Graduate School of the Environment Centre for Alternative Technology, Machynlleth, Powys, SY20 9AZ, UK. tel:

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1 Graduate School of the Environment Centre for Alternative Technology, Machynlleth, Powys, SY20 9AZ, UK tel: School of Computing and Technology University of East London Docklands Campus 4-6 University Way London E16 2RD tel: i

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3 A Methodology for Evaluation of an Energy Efficient Refurbishment of a Typical 1960 s semi-detached Dublin House in Line with Ireland s 2020 National Goals Patrycja Kochaniuk July 2012 iii

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5 Abstract This study aims to develop a methodology for evaluation of an energy efficient refurbishment for a typical 1960 s semi-detached Dublin house. The research offers an individual approach to the retrofit of this specific building type and provides general guidelines as to how to choose the suitable measures and analyse their performance taking into account different priorities. The problem is investigated in two stages. First, the suitable measures for building fabric and new ventilation strategies are described and evaluated. Four levels of upgrades achieving different depths are proposed. Their suitability with regards to the building physics is explored and possible space heating energy savings are calculated. The suitable new heating systems and renewable technologies are also proposed and their impact on the primary energy use is assessed. The second stage analyses both the building fabric upgrade levels and different heating system options under economic, environmental and social factors. It quantifies the CO 2 emission and monetary savings associated with the different options of refurbishment using the life cycle analysis. The final conclusions propose optimal solutions taking into account all the factors. This study shows that a refurbishment of all the building fabric elements and a new ventilation system can bring serious space heating cuts. The four levels of upgrades can ensure between 82% and 99% of savings in space heating energy comparing to the original house s performance. When looking at the whole house s heating related primary energy use, the building fabric upgrades with ventilation and new heating systems can provide between 77% and 96% savings depending on the level of upgrades and the system type. Even though the higher levels of upgrades provide more CO 2 savings, they prove to bring less return on the investment. This study discusses the discrepancy between financial, environmental and social aspects of the different levels of upgrade and makes recommendations aiming at addressing it. Ireland agreed along with the EU to substantial cuts in CO 2 emissions but in 2012 it is still not on the right track to realise its commitments. This thesis analyses the existing CO 2 emission saving plans and investigates possible additional cuts that can be achieved in construction sector. It points out deficiencies in the current programmes and proposes to include more comprehensive solutions for addressing the existing problematic housing sector. It suggests introducing more efficient incentives using the example of German and British approach for financing deep retrofit. v

6 Table of Contents Title page...iii Abstract...v Table of Contents...vi List of Chapters...vii List of Figures...x List of Tables...xi List of Appendices...x List of Abbreviations...xiii vi

7 List of Chapters 1 Introduction Literature Review: EU goals and domestic energy efficiency in Ireland, UK and Germany EU directives Ireland s government goals for the energy reduction in housing and existing practice in low energy refurbishment Other countries approach UK Germany Lessons for Ireland Literature Review: existing procedures for calculating energy use in dwellings and methodologies for the low-energy refurbishment Energy use calculation DEAP PHPP and Passivhaus Existing methodologies for the low-energy refurbishment Tarbase model Toolbox approach Summary Methodology Methodology overview Methods of data gathering Evaluation of measures (Chapter 5) Analysis of data (Chapter 6) Refurbishment strategies optimal measure choice and calculation results Existing conditions a case study dwelling Building fabric refurbishment and ventilation reducing space heating demand Floor insulation Wall Insulation Roof insulation Windows and doors replacement Combined building fabric savings Air tightness Layout and windows modification improving solar gains Ventilation strategy...31 vii

8 5.2.9 Summary Energy efficient equipment reducing space and water heating energy use Water heating Fossil fuel heating systems Renewable heating Summary of the heating systems options Analysis results Environmental impact Annual CO 2 savings due to reduced energy use for space heating Annual CO 2 savings due to improved efficiency of heating system and different fuel options for Levels A to D Summary Economic validation Summary of capital costs for the four levels of the fabric upgrade Running cost of the heating system in existing house Economic analysis of the building fabric upgrade levels Economic analysis of the heating systems Summary Social considerations Discussion Environmental factor Economic factor Social factor Summary Governmental incentives Conclusions Summary of the findings Limitations Further research References...62 Appendix A PHPP methodology...65 Appendix B Tarbase methodology...67 Appendix C Comparison between DEAP, PHPP and Tarbase methodologies...69 Appendix D Existing house specification and baseline settings for PHPP...71 Appendix E Summary of capital costs for all refurbishment measures...73 Appendix F Phenolic insulation between timber joists...77 viii

9 Appendix G The influence of thermal mass...78 Appendix H U-value calculations...79 Appendix I Internal or external wall insulation?...83 Appendix J Window rating...84 Appendix K Direct solar gain strategy...86 Appendix L Ventilation strategies...87 ix

10 List of Figures Figure 1. Example output of the Tarbase Domestic Model. From: Jenkins at al. (2012)... 8 Figure 2. Case study house existing plans Figure 3. Case study house existing elevations Figure 4. Existing suspended timber floor insulation. Adapted from: EST (2011) Figure 5. Existing suspended timber floor replaced by concrete floor with insulation above the slab. Adapted from: Energy Saving Trust (2011)...19 Figure 6. Existing suspended timber floor replaced by concrete floor with insulation below the slab. Adapted from: Energy Saving Trust (2011)...19 Figure 7. Section through internally insulated external wall Figure 8. Section through externally insulated external wall Figure 9. Thermal bridge at wall ceiling junction Figure 10. Wall ceiling junction thermal bridge reduced Figure 11. Window installation with minimised thermal bridge Figure 12. Changes in windows layout that allow maximising direct solar gains Figure 13. Changes in plan layout that allow maximising direct solar gains Figure 14. Annual CO2 emission savings for Levels A, B, C and D Figure 15. Comparison of annual CO2 emissions for different heating systems x

11 List of Tables Table 1. Projected Energy Savings 2020 for residential sector - adapted from: Ireland. Department of Communications, Energy and Natural Resources, Table 2. Adapted from: UK. Department of Energy and Climate Change (2011)... 5 Table 3. Assumed lifespan of ventilation and heating systems Table 4. Irish governmental incentives for existing house retrofit Table 5. Maintenance costs of ventilation and heating systems Table 6. Fuel costs for 2011 (SEAI, 2012)...14 Table 7. Floor refurbishment options...20 Table 8. Wall refurbishment options...23 Table 9. Ceiling refurbishment options...25 Table 10. Window replacement options...27 Table 11. Combined effect of building fabric upgrade options...28 Table 12. Combinations of fabric upgrade options and air tightness measures...29 Table 13. Possible energy savings for each upgrade level due to increased solar gains...31 Table 14. Energy savings for different upgrade levels...32 Table 15. Accumulation of space heating energy savings for each upgrade level...32 Table 16. Average daily hot water usage...33 Table 17. Energy savings due to a boiler upgrade (regular boiler) and its capital cost Table 18. Energy savings due to a boiler upgrade (combi boiler) and its capital cost Table 19. Energy savings due to a biomass boiler upgrade and its capital cost Table 20. Energy savings due to solar water heating installation and its capital cost Table 21. Energy savings due to a heat pump upgrade and its capital cost Table 22. Energy savings in Primary Heating Energy Demand due to the different heating system upgrade options Table 23. Breakdown of CO2 emissions components for the original heating system for four levels of building fabric upgrade Table 24. Breakdown of CO2 emissions for the new regular gas boiler heating system Table 25. Breakdown of CO2 emissions for the regular gas boiler heating system and solar DHW Table 26. Breakdown of CO2 emissions for the components for the upgraded combi gas boiler heating system for four levels of building fabric upgrade Table 27. Breakdown of CO 2 emissions for the wood pellet stove heating system...42 Table 28. Breakdown of CO2 emissions for the wood pellet stove heating system and solar DHW Table 29. Breakdown of CO2 emissions for the heat pump heating system Table 30. Breakdown of CO2 emissions for the heat pump heating system and solar DHW xi

12 Table 31. Summary of Capital Costs for all the refurbishment measures for four levels of fabric upgrade Table 32. Annual Costs of Delivered Energy for existing heating system in existing house Table 33. Annual Investment Costs for four levels of upgrade with old boiler heating system...46 Table 34 Annual Costs of Delivered Energy for the old boiler heating system Table 35 Annual Savings due to four levels of building fabric and ventilation upgrade Table 36. Annual Investment Costs for regular gas boiler heating system Table 37. Annual Investment Costs for regular gas boiler heating system plus solar DHW Table 38. Annual Costs of Delivered Energy for new regular condensing gas boiler heating system and the same system with solar DHW installation Table 39. Annual Investment Costs for combination gas boiler heating system Table 40. Annual Costs of Delivered Energy for four levels of fabric upgrade and new combination gas boiler heating system Table 41. Annual Investment Costs for biomass boiler heating system Table 42. Annual Investment Costs for regular gas boiler heating system plus solar DHW Table 43. Annual Costs of Delivered Energy for biomass boiler heating system without and with the solar DHW Table 44. Annual Investment Costs for heat pump heating system Table 45. Annual Investment Costs for heat pump heating system and solar DHW Table 46. Annual Costs of Delivered Energy for heat pump heating system without and with solar DHW Table 47. Annual Investment Costs for each upgraded heating system Table 48. Annual Costs of Delivered Energy for each upgraded heating system Table 49. Annual savings due to the level A refurbishment for each heating system Table 50. Annual savings due to the level B refurbishment for each heating system Table 51. Annual savings due to the level C refurbishment for each heating system Table 52. Annual savings due to the level D refurbishment for each heating system Table 53. Summary of CO2 emissions savings for all heating systems for all upgrade levels Table 54. Summary of monetary savings for all heating systems for all upgrade levels Table 55. Cost effectiveness of carbon reduction for level A refurbishment, for all heating system options Table 56. Cost effectiveness of carbon reduction for level B refurbishment, for all heating system options Table 57. Cost effectiveness of carbon reduction for level C refurbishment, for all heating system options Table 58. Cost effectiveness of carbon reduction for level D refurbishment, for all heating system options Table 59. CO 2 emissions savings in xii

13 List of Abbreviations The following abbreviations have been used in this document: AE BER BES CFL COP DCMV DEAP DHW DPM EBS EPBD ESCO EU EWI GHS HES ipsv KfW MVHR NZEB PHE PHPP PSV RD&D Programme SAP SEAI SH Tarbase WH VHEPB Auxiliary Electricity Building Energy Rating Better Energy Scheme Compact fluorescent lamp Annual coefficient of performance Demand control mechanical ventilation Dwelling Energy Assessment Procedure Domestic hot water Damp proof membrane Efficient Standard Energy Performance of Buildings Directive Energy Service Company European Union External Wall Insulation Greener Homes Scheme Home Energy Savings Intelligent passive stack ventilation Kreditanstalt fuer Wiederaufbau mechanical ventilation with heat recovery Nearly zero-energy buildings Primary Heating Energy Passive House Design Package Passive stack ventilation Research, Development and Demonstration Programme Standard Assessment Procedure Sustainable Energy Authority of Ireland Space heating Technology Assessment for Radically Improving the Built Asset base Warmer Homes Very high energy performance buildings xiii

14 1 Introduction Energy efficient refurbishment of old properties is a complex task and homeowners may feel confused as to what measures are optimal for the specific situation and what depth of the retrofit is the most beneficial. There is a substantial amount of information available, for example from the governmental bodies, but usually in a form of a general advice for all possible measures and choices and they are not specifying what results can be expected. At the same time, the European Union has committed to reduce the greenhouse gas emissions by at least 20% below 1990 levels until 2020 (European Parliament, 2010). Since the built environment uses 40% of the total energy consumption in the EU, reduction in CO 2 emissions in this sector can have a significant impact. This study aims to develop a methodology for evaluation of an energy efficient refurbishment of a specific example house type. Its unique character is based on the two-sided approach regarding both the best interest of the homeowner and the wider environmental point of view represented by the governmental bodies. This research attempts to find refurbishment options optimal for both parties, discusses the possible conflicts of interests and ways of addressing them. The thesis begins with a discussion of the EU countries commitments with regards to CO 2 emissions reduction. In Chapter 2 the current situation in Ireland is compared with British and German approach and conclusions are drawn. Chapter 3 investigates the existing methodologies both for calculating the energy use and for the existing houses refurbishment and then proposes an optimal approach for the case study house. Afterwards, in Chapter 4 a methodology is further developed, including strategy for choosing the appropriate refurbishment measures and their analysis. The proposed measures are discussed in Chapter 5 in detail. Their correct use is illustrated and explained. The suggested measures for building fabric and ventilation upgrade are combined in four options, proposing different levels of space heating energy savings. Also all available and suitable heating systems are presented and evaluated in the light of possible to achieve cuts in primary energy use. In Chapter 6, the four levels of upgrades are analysed in the light of environmental, economic and social factors and the best performing combination of measures is proposed considering different priorities. The proposed heating systems are examined in conjunction with all the upgrade levels and the best performing ones are chosen. Finally, the influence of this refurbishment on achieving the national goals is discussed in Chapter 7 and possible governmental incentives helping both the homeowners and the environment are investigated. The study concludes with outlining the limitations of this approach and discussing necessary further research. 1

15 2 Literature Review: EU goals and domestic energy efficiency in Ireland, UK and Germany 2.1 EU directives Directive 2010/31/EU (European Parliament, 2010) required Member States to develop policies to stimulate the refurbishment of existing buildings to the same high standard as with regards to new buildings and include minimum energy performance requirements for major renovations. As a result of slow response, a new Energy Efficiency Plan has been developed (European Commission, 2011) to improve the pace of changes by the Member States through their National Plans. It warns that in case of no improvement, the legally binding national targets for 2020 will be imposed in The new document recognizes deficiencies in current approach by Member States and proposes that the scope of the national frameworks, represented in National Energy Efficiency Action Plans, is expanded to capture more energy saving potentials. With regards to energy savings by buildings renovation, the Commission recognizes its unrealized potential and proposes to strengthen the role of the Energy Service Companies (ESCOs) as catalysts for renovation. 2.2 Ireland s government goals for the energy reduction in housing and existing practice in low energy refurbishment The first National Energy Efficiency Action Plan (Ireland. Department of Communications, Energy and Natural Resources, 2009) specifies the target of 20% reduction in energy demand through proposed actions by 2020, comparing to average energy use of the levels of period. The total energy savings needed to meet that requirement was calculated at 31,925 GWh/y. The document presents energy efficiency improvement actions divided by sectors that are estimated to provide 23,730 GWh/y of the savings. This constitutes nearly 15% of the committed levels by 2020, not yet meeting the targeted value. Residential sector represents nearly 44% of the total planned savings at 10,355 GWh/y. The action plan presents two major challenges in relation to residential sector: to create energy efficient new dwellings and to address the high energy use and CO 2 levels of the existing housing stock. The actions concerning increasing the energy efficiency in new buildings include mainly changes in consecutive Building Regulations regarding conservation of fuel (points 1 to 4 in Table 1). The only RD&D programme, the House of Tomorrow scheme (point 5) was a grant support for housing exceeding current building regulations requirements by 40%. It supported 5,000 new houses in , but it is discontinued. The projected total savings based on new buildings related actions are 5,030 GWh/y and 1,258 ktco 2 /y (sum of points 1 to 5). 2

16 Energy efficient improvement programmes, energy services and other measures aiming to improve energy efficiency Annual energy savings expected by Building Regulations 2002 improved energy performance of residential buildings 2. Building Regulations % improvement on energy performance of residential buildings relative to 2002 building regulations 3. Building Regulations % improvement of residential buildings relative to 2002 building regulations 4. Low Carbon Homes % improvement of residential buildings relative to 2002 building regulations 5. House of Tomorrow Programme developer support for buildings exceeding existing building regulations GWh/y ktco 2 /y 1, , , Warmer Homes Scheme Home Energy Saving scheme improving current residential building stock in Ireland Greener Homes Scheme Smart meter installation estimated efficiency gains among domestic users Ecodesign for Energy-Using Appliances (Lighting) 1, Efficient standard 2, Total Residential Sector 10,355 2,436 measures relating to new buildings measures relating to existing buildings Table 1. Projected energy savings for residential sector. Adapted from: Ireland. Department of Communications, Energy and Natural Resources, With regards to existing dwellings, most of the savings (points 10 and 11 totalling at 3,600 GWh) are based on the Efficient Standard (EBS) and Ecodesign for Energy-Using Appliances (Lighting). EBS is assuming that all existing boilers will have to be replaced by 2020 to 90% efficient ones, as per the requirement of latest building regulations (Ireland. Department of Environment, Heritage and Local Government, 2011). The Ecodesign relates to incandescent bulbs being replaced by compact fluorescent lamps (CFLs). Those measures do not require any action other than perhaps the regulations enforcement. The main measures requiring actions include grant schemes (points 6, 7 and 8 suggesting savings of 1,035 GWh/y) and installation of smart meters (point 9-690GWh/y). Warmer Homes (WH) scheme supported upgrading homes occupied by those on low incomes (up to 100% of installation cost), Home Energy Savings (HES) was assisting energy upgrades of older homes for any homeowners (about 30% of installation cost) and Greener Homes Scheme (GHS) supported new installations of renewable energy appliances in existing buildings. In 2011 WH, HES and GHS were combined into Better Energy Scheme (BES), the grant sums were reduced and grants for renewable heating systems except for solar thermal, were cancelled (Ireland. Department of Communications, Energy and Natural Resources, 2012). Thus it is possible that the savings projected in 2009 may not be achievable any more. 3

17 Total savings potential of residential sector (10,355 GWh/y) consists of: 49% of measures relating to new building regulations, 35% savings from boiler and light fixtures replacement, 10% grants and 7% smart meters installation. Only the grant schemes have direct impact on the housing refurbishment, so it can be said that the potential for savings in this sector is not yet fully exploited. More importantly, although the grants are addressing a large number of houses, they allow for refurbishment of one or more building elements (measures include wall and roof insulation, heating controls with or without a new gas or oil boiler and installation of solar panels for water heating). SEAI report (2009) lists 33,400 measures implemented in 18,100 homes. The most recent one (SEAI, 2010) shows an increase to 82,900 measures in 46,000 homes, but the average of the measures per house stays at the same level at 1.8. The requirement for upgrades is to bring those elements to 2008 building regulations standard, and it is still valid in the beginning of 2012, despite the introduction of more restrictive regulations in 2011 (Ireland. Department of Environment, Heritage and Local Government, 2011). The grant scheme plays an important role with regards to development of skills of tradesmen and increasing awareness of importance of energy efficiency among the public, but its impact on the overall savings in residential sector is quite small (10%). In addition to that, the 2007 National Action Plan did not introduce any measures for realizing the Directive 2010/31/EU recommendation for stimulation of deep retrofits. However, it pointed out a potential for more savings in existing stock that needs to be explored in the future, so ways of realizing deep retrofit opportunities should be further explored. The national Action Plan was due to be revised in 2011 but at the time of writing the thesis the revision is still not available. It is worth mentioning that also the latest revision in building regulations, envisaged in 2010 was actually realized in the end of 2011, so it is evident that legislation tends to be lagging behind the high-level goals. A report by CODEMA DIT Partnership (2005), presented in Colley, J. (2011), researched Irish homes in houses built between 1997 and 2002 were checked for compliance with Part L of Irish Building Regulations current at the time and only one of them fully complied. Such dwellings would be expected to use 41% less energy comparing to those constructed in due to the amendments to the Building Regulations since However, the report stated that the actual energy use decreased only by 13%. That discrepancy was explained as a combination of two factors: faulty installation of prescribed measures and increased comfort expectations. It was noted that although the fabric insulation was 87% compliant where it was reported by a normal inspection, the infra red technology has revealed that 15% of dwellings had insulation defects concealed within the wall and roof constructions, which contributed significantly to heat losses. 92% of houses did not meet the minimum insulation requirements for pipes, ducts and hot water cylinders and 63% had insufficient heating controls. Also 44% of boilers failed to meet the minimum efficiency level. The findings of this report proved that the building control failed in Ireland at the time and since regulations with that respect did not change until now, it can be expected that the problem persists. To conclude, the report shows that it is not reasonable to base the energy saving forecasts solely on the base of the building regulations prescriptions until their enforcement is improved. 2.3 Other countries approach UK In their report, UK. Department of Energy and Climate Change (2011) evaluated the energy savings introduced in British National Action Plan in 2007 and proposed ideas for further governmental policies. That analysis revised the original calculation methodology, eliminating savings from overlapping policies. The new report sets out energy savings of 18% by 2020, not yet meeting the 20% energy use savings as specified by EU. 4

18 Table 2 shows a total savings potential of residential sector (153 TWh/y). It consists of: 32% of measures relating to building regulations, 12% product policies, 43% savings from supplier obligation related measures, 8% grants and 5% smart meters installation. Comparing to Irish plans, UK proposes more actions relating to existing housing. The biggest part of it, the supplier obligations, is a program committing the energy suppliers to promote energy efficiency measures (low energy lighting, insulation, etc.) and offer free or subsidized help. Grants supported by the government only relate to tackling fuel poverty and supporting renewable heating. Energy efficiency improvement programmes, energy services, and other measures to improve energy efficiency planned for achieving the target Annual energy savings expected by end of 2010 Annual energy savings expected by end of 2016 Annual energy savings expected by end of 2020 TWh/y MtCO 2 /y TWh/y MtCO 2 /y TWh/y MtCO 2 /y Building Regulations Supplier obligations (Energy Efficiency Commitment, Carbon Emissions Reduction Target, the Community Energy Savings Programme) - for existing houses Products policy In home displays / Smart meters Renewable Heat Incentive Warm Front Household sector Table 2. Adapted from: UK. Department of Energy and Climate Change (2011) The consultation Building a Greener Future: Towards Zero Carbon Development (UK. Department for Communities and Local Government, 2006) lists a number of new policies announced to be developed in near future. Regarding tacking the existing dwellings, it proposes the Green Deal financing energy efficient retrofitting in homes and businesses through energy bill savings. The packages of measures would be expected to bring enough return to pay back for investment over the specified time. It is also planned for 2016 to oblige private landlords to implement energy efficient improvements suggested by their tenants and by 2018 to require them to upgrade the least efficient properties Germany Schimschar at al. (2011) analysed the German potential in realizing the requirements of the Directive 2010/31/EU by researching the influence of governmental initiatives on energy efficiency in buildings. The study evaluated the past achievements of the policies and analysed the findings to predict possible future developments. 5

19 For the purpose of the study the authors defined the nearly zero-energy buildings (NZEB) as those with the primary energy demand for space heating of maximum 20 kwh/m 2 /y both for new and existing dwellings and very high energy performance buildings (VHEPB) with space heating demand of max. 40 kwh/m 2 /y. They postulated the need to start implementing climate neutral refurbishments already in 2020, as the Germany s long distance goal is to have nearly climate neutral building stock by 2050 and typical refurbishment intervals are 30 years. The Kreditanstalt fuer Wiederaufbau (KfW), governmentally owned bank has been providing subsidies for new and refurbished houses constructed to exceed the building regulations since Based on KfW data and Passivehaus certification numbers, Schimschar at al. (2011) estimated that there were 335,000 VHEPBs in Germany in 2009, constituting 1% of the building stock. The study concluded that the NZEB standard could be achieved in 2020 with the gradually improving building codes. However, the 20% target for reducing the energy in the whole building stock appeared to be very ambitious. The study showed that it would only be possible with the most dramatic changes in building regulations and high rates of refurbishment, demolition and new construction. The study also shows that the energy use in the whole building stock is more influenced by deep energy renovation of the existing stock than by ambitious changes in building codes regarding new buildings Lessons for Ireland To enable savings of the CO 2 emissions in existing housing stock on a bigger scale, the initial grant programme should be transformed to a more comprehensive approach in Ireland. The German and English ideas for financing deep retrofit projects could be an example for the Irish model. The German concept of conditioning the subsidies on the extent of energy savings due to the retrofit would encourage homeowners to choose deeper refurbishment solutions. The UK s proposal of a programme with favourable loan interest rates for energy efficient refurbishment, where the upgrades are expected to pay for themselves over their lifetime could make the energy efficient retrofit financially viable. 6

20 3 Literature Review: existing procedures for calculating energy use in dwellings and methodologies for the low-energy refurbishment 3.1 Energy use calculation DEAP Dwelling Energy Assessment Procedure (DEAP) is a procedure and a software tool that calculates the energy use of dwellings in Ireland (SEAI, 2012C). It follows the method from the EU Energy Performance of Buildings Directive (EPBD) and is based on the Standard Assessment Procedure (SAP), an official UK methodology. It is designed for the purpose of demonstrating compliance with the EPBD in Ireland. DEAP calculates the primary energy consumption and carbon dioxide emissions. It estimates the energy use for space and water heating, ventilation and lighting and deducts savings from energy generated on site and from solar and internal gains. The factors influencing the energy use are: size, geometry and exposure of the building, thermal properties (U-values) of the building fabric elements, windows characteristics, ventilation type, efficiency, responsiveness and control of the heating system, thermal mass of the building, fuels used to produce the energy and finally the renewable energy sources. The Building Energy Rating (BER) calculation uses certain assumptions regarding the pattern of occupant s behaviour, for example internal temperatures, duration of heating and usage of electrical appliances, etc. The procedure uses one climatic data set for any Irish location. It is not possible to modify any of the assumption settings (SEAI, 2012C) PHPP and Passivhaus Passive House Design Package (PHPP) is an MS Excel-based model for calculating the energy performance of buildings. It acts as a verification tool for Passivhaus, the voluntary building standard developed in Germany, but was adapted for different climates throughout Europe (Feist at al., 2007). The main idea of the Passivhaus is to reduce building s heat losses to such a small amount that a separate space heating system is not needed. To allow for that, the specific annual demand for space heating must be kept under 15 kwh/m²/y. Also the final energy demand for space and water heating, ventilation and household electricity cannot exceed 120 kwh/m²/y. The house s overall heating requirements have to be verified by PHPP and depend not only on the building s elements performance and equipment specification but also on its compactness and orientation, so a holistic design approach is required. The general rule calls for the U-values for walls, roofs and floors at 0.15 W/ m²k, windows U-value not exceeding 0.8 W/m²K and a use of MVHR system, min. 80% efficient. These values are valid for the Central Europe conditions, and as set out by Sustainable Energy Ireland (2009), can be relaxed for a milder Irish climate. PHPP calculations are based on a set of Excel sheets that allow for modifications. A detailed methodology can be found in Appendix A. Passivhaus standard has been originally developed for new dwellings, but the same principles apply for the retrofitted houses. It has been however recognised that sometimes upgrading of the existing buildings can encounter situations difficult to solve, like unavoidable thermal bridges or restrictions in insulation depth etc. That is why the Passivhaus Institute eased the requirements for retrofitted buildings to the EnerPHit standard (annual demand for space heating requirement is changed from 15 kwh/m²/y to 25 kwh/m²/y and max. air change rate at pressurization test from 0.6 ac/h to 1.0 7

21 ac/h). However, the enlarged space heating demand may require an installation of additional heating supply, so a consideration in this regard is necessary. 3.2 Existing methodologies for the low-energy refurbishment Tarbase model Jenkins at al. (2012) describe a Technology Assessment for Radically Improving the Built Asset base (Tarbase), an assessment model calculating the energy use in buildings. As it is designed specifically for refurbishment, it includes choices of carbon-saving measures that can be applied to investigated dwelling. The model was developed to allow for climate, internal activity and occupancy variations as opposed to the other available tools (for example SAP) that treat all buildings in the same way what provides unreliable results. The authors concluded that in order to be able to achieve useful output from a steady-state model like Tarbase, it has to be flexible in allowing variability in some inputs. The tool is producing automated output, such as in Fig.1, demonstrating the annual CO 2 emissions due to space and water heating and appliances and lighting energy use. Figure 1. Example output of the Tarbase Domestic Model. From: Jenkins at al. (2012) Tarbase allows for calculating the effects of different measures that can be applied in any order and is showing the accumulated results (as shown in Fig.1). It allows the user to choose refurbishment options from a list of demand side interventions (appliances and lighting, fabric improvements, infiltration and ventilation rates, heating systems etc.) and supply side measures (solar thermal water heating, photovoltaic panels, micro combined heat and power and heat pumps). Details of the methodology can be found in Appendix B. 8

22 3.2.2 Toolbox approach Konstantinou and Knaack (2011) present a methodology used for a design of energy efficient refurbishment of an apartment block in Germany, where the indicator used was the heating demand. They proposed to identify the possible refurbishment measures and then assess how each of them contributes to the energy efficiency upgrade. They isolated the impact of each option by first modelling the room in existing apartment and its heating demand for each orientation. Then, based on this model, each upgrade option was simulated separately, by changing only one component in the model. Finally, the impact of each measure was quantified as the percentage of reduction to current energy demand. They proposed to list the results to create a toolbox, organised according to the efficiency of the measures, including variations of the specifications of the construction details (e.g. the insulation thickness). The authors explained that the purpose of the individual calculations is to provide an assessment of the impact of the different options to provide guidance for designer in a form of a database of solutions. The toolbox options could also include resolution of the technical issues likely to occur during the upgrade implementation. 3.3 Summary Appendix C summarizes the performance of DEAP, PHPP and Tarbase models. DEAP is tailored for Irish conditions but some of its unrealistic assumptions restrict the possibility of flexible adjustment to a specific situation. The Tarbase model is much more flexible and includes features useful for the retrofit situation, but it was developed for the British climatic conditions and is not yet available commercially. PHPP Excel worksheet appears to be the most flexible and easy tool for energy use calculation. It can be adapted both for Irish conditions and for specific occupancy and is readily available. That is why it is proposed to use it for the case study house calculations of the space heating demand and primary energy demand to compare the impact of the different upgrade measures. The Tarbase model s elements worth adapting are the specific list of refurbishment options and its ability to show the cumulative effects of designed measures which can be compared with the original condition. Chapter 4 presents the methodology for developing such a list for a case study house. The toolbox approach from the Konstantinou and Knaack (2011) study can also be adapted to show the differences in energy savings between the different measures. 9

23 4 Methodology The review of literature carried out in Chapter 2 set out the need for reducing energy use in domestic sector in Ireland and pointed out possible unrealized energy savings in existing housing retrofit. It also discussed the lack of the existing guidance and legislation encouraging deep retrofit projects. Chapter 3 then presented several existing tools for energy use calculation and retrofit strategies that could be adapted for the purpose of deep retrofit methodology suitable for Irish conditions. This chapter introduces the link between the findings from literature review and the proposed investigations. Finally, it sets out a framework of steps to be taken to arrive at a methodology for evaluation of an energy efficient retrofit of the case study house. 4.1 Methodology overview This paper s methodology draws ideas from the described earlier models but proposes to add some new features. It is proposed to calculate the energy use of the building and associated CO 2 emissions using the PHPP tool, with baseline settings described in Appendix D. It is the most flexible software as explained in the summary of Chapter 3, so can be easily adapted. It is proposed to use the Tarbase model s idea to include a choice of specific measures suitable for the deep retrofit. However, the novelty of this research includes the evaluation of the proposed suitable measures for building fabric refurbishment with explanation why they were chosen. So it not only presents a list of choices, but also advises why one is better than others. As opposed to the models described earlier, this study has an individual approach to a specific building type. Its purpose is to support the particular house type owners in decision making, but it is also providing a methodology that can be adapted for other building types. The methodology has two steps. The first, discussed in Chapter 5 proposes measures for building fabric, ventilation and heating system upgrade. It introduces qualitative approach to provide solutions optimal from the building physics point of view and offers calculations for possible energy savings. The second stage, shown in Chapter 6 analyses the proposed solutions of building fabric and ventilation upgrades, followed by the heating system options under economic, environmental and social factors in the quantitative manner. It uses the life cycle analysis to calculate CO 2 emission and monetary savings associated with the different options. Another innovative approach includes looking at the refurbishment task not only from the homeowner s point of view, but also locating the problem in the wider national aspect. In Chapter 7 the study discusses Ireland s environmental commitments and proposes to integrate the homeowner s and national goals to achieve better results. It is also investigates possible governmental incentives in the light of examples of German and British approach described in Chapter Methods of data gathering Evaluation of measures (Chapter 5) Chapter 5 provides information on all suitable upgrading measures and qualitative evaluation of the proposed four levels for each element. The steps include: 1. Presentation of the case study existing house and its energy use calculated using PHPP. 2. Evaluation of measures providing space heating energy savings: a. Evaluation of approaches for fabric elements (floor, walls, roof, windows) upgrade includes the review of all the possible choices available and their suitability for this particular application. Then four levels from the simplest Level A to the most complex level D are 10

24 proposed for each measure. Calculations showing space heating energy savings are done in PHPP, using settings described in Appendix D. For each element, the improved space heating energy for each option is compared with the original house s heating demand to show their isolated impact. b. Calculation of the combined effect of the building fabric upgrades shows the impact of all the upgrades. c. Discussion on options for air tightness upgrade and calculations of accumulated energy savings. d. Discussion on windows location and size and plan layout. Calculations show the impact of improved solar gains on space heating energy for the same layout and window changes for each level. e. Discussion on ventilation options and their impact on energy savings. 3. Discussion of heating system upgrades including options for traditional approach and renewable options measures providing savings in primary energy use. In this chapter, all initial capital costs of installing each of the measure variations in the case study house are estimated from the fee quotations from contractors for similar works on different projects from the past year and from supplier price lists published online. The assumed prices are summarized in Appendix E Analysis of data (Chapter 6) Chapter 6 provides qualitative analysis of the upgrade options in the light of environmental, economic and social factors. 1. Environmental analysis focuses on the impact of carbon emissions from the ventilation and heating systems. The full life cycle analysis, taking into account the recourse depletion, embodied energy and waste could provide more information helping to guide the choice of materials and systems but unfortunately is not in the scope of this work. Thus, the calculations take into account only operational CO 2 emissions. Also household appliances and lighting electricity is not included here as the study focuses on aspects connected directly with the building envelope. The environmental benefits of an energy efficient refurbishment are calculated by deducting the CO 2 emissions due to decreased energy use for heating and running the ventilation and heating systems from the original house s CO 2 emissions. The delivered energy is multiplied by a CO 2 emission factor associated with each fuel, as explained below. Thus, the final amount of CO 2 emissions is influenced both by lower energy use and by the type of fuel. The calculations are done in two stages: a. CO 2 savings due to reduced space heating energy use (section ) Space heating energy savings and electricity use associated with running ventilation and heating (auxiliary electricity) for each option are calculated using PHPP methodology described earlier. Savings associated with each implemented measure are shown separately as they are gradually applied to the original house. The CO 2 emissions are calculated using the gas emission factor for the original heating system. The differences of the impact of the four levels of upgrades are discussed. Fabric and ventilation refurbishment impact only the space heating, so hot water production is not affected here. Thus the savings are realised only in space heating (SH) and auxiliary electricity (AE). As the space heating is realised by a gas boiler and electricity comes from grid, the CO 2 emission factor is kg/kwh for gas and kg/kwh for electricity respectively. These factors are taken from DEAP as it is considered more accurate for Irish circumstances rather than Germany based PHPP factors. 11

25 b. CO 2 savings due to improved efficiency of heating system and different fuel options (section ) The efficiency of the boiler system impacts both space and water heating, so in this section CO 2 emissions are calculated and compared for all energy demand, except for household and lighting electricity (as explained earlier). The biomass boiler and heat pump heating systems are compared with the traditional gas boiler approach, all of them with and without an addition of solar DHW. CO 2 levels are shown for all components (space heating, water heating and auxiliary electricity) separately to compare the influence of different fuels and the extent of emissions that can be eliminated by the solar thermal heating system. CO 2 emission factors: kg/kwh for gas, kg/kwh for electricity and 0.05 kg/kwh for wood pellets are taken from DEAP as explained earlier. 2. Economic validation. The whole life cost analysis verifies the economical viability of the refurbishment project options. It includes calculation of capital investment, maintenance and running costs. First, the capital cost for all improvement measures are summarized for levels A to D. The prices for capital investments are shown in Appendix E. Next, the running cost of existing heating system in the original case study house is established for comparison purposes. Economic analysis for all the heating system options is conducted in the following steps: a. Capital cost of improvements from table 31; b. Additional cost over 30 years. In the case study house, the building fabric life span is assumed to be 50 years and the life span for mechanical systems is set out in Table 3. It was decided to perform the whole life cost calculation over 30 years in order to capture the balance during the assumed loan term. For ventilation and heating systems with a lifespan shorter than 30 years, it is assumed that the cost of replacement will be the same for the similar equipment performance in future. Ventilation strategy Lifespan [years] PSV 50 DCMV 15 MVHR 15 Heating strategy Lifespan [years] Gas condensing boiler 15 Biomass boiler 30 Heat pump 15 Solar DHW 15 Table 3. Assumed lifespan of ventilation and heating systems. c. Governmental incentives are then deducted from the capital cost. They are summarized in Table 4 for the present situation (SEAI, 2012B) SEAI Grant 'Better Energy Home' Value Gas boiler + controls 560 Attic insulation 200 External Wall insulation 2700 Solar Heating 800 Table 4. Irish governmental incentives for existing house retrofit. 12

26 d. It is assumed that the building components expected lifetime is 50 years. Thus, they will have a residual value left after the 30 year loan is paid, which should be deducted when calculating the relevant investment costs. The residual value of building envelope investment after 30 years can be calculated with the following formula: R = (1-(A product life x P.V.F. loan term )) x I, where: -n(product life) A product life = p r /(1-(1+p r ) P.V.F. loan term = (1-(1+p r ) -n(loan time) )/ p r A product life = Annuity factor for the product life P.V.F. loan term = Present value factor for the loan term I = Investment cost (in this case - the fabric upgrade cost) p r = real loan interest rate n = number of years e. Final cost of improvements over the 30 years of loan is calculated as a sum of capital cost, additional costs for replacement of mechanical systems with the life shorter than 30 years minus grants and residual value of components with a life longer than 30 years. f. The cost of annual loan repayment can then be calculated by an annuity calculation method, using the following formula: Annuity = Final Cost of Improvements during loan term x Annuity factor (A), where A= p r /(1-(1+p r ) -n, and p r = ((1+ p n ) / (1 + i)) -1, and A = annuity factor, p r = real loan interest rate, n = number of loan years, p n = nominal loan interest rate, i = inflation rate. For the purpose of calculations a loan for 30 years at a rate of 4% and inflation at 1.5% is assumed. g. Annual maintenance costs cover the necessary servicing (Table 5). Those assumptions are the best guess based on review of manufacturers information published online and from earlier study of Woodhead (2010). 13

27 Maintenance required Annual Cost Ventilation strategy PSV Cleaning of vents every 5 years 40 DCMV Annual cleaning of vents 200 MVHR Annual cleaning of vents and filters 300 Heating strategy Gas condensing boiler Annual servicing (by qualified installer) 150 Biomass boiler Cleaning every 2-4 days (by the occupant), Bi-annual servicing (by qualified installer) 100 Heat pump Annual servicing (by qualified installer) 200 Table 5. Maintenance costs of ventilation and heating systems. h. The total annual spend on improvements over the 30 years of loan is a sum of annual loan repayments and annual maintenance cost. i. Annual cost of delivered energy is calculated for fuels and electricity used for ventilation and heating options. Prices published by SEAI (2012) are used (Table 6). The heating energy use for gas (or pellets) and electricity, taken from calculations in PHPP are multiplied by the cost of kwh of each fuel. These calculations are excluding household electricity use (lighting and appliances) as they are focused on energy connected with heating. The actual delivered energy values are taken into account here, as these are the amounts of kilowatt-hours that the occupants are paying for. The future possible rises of energy prices are not taken into account. Fuel Price per kwh Natural gas Pellets (bulk delivery) 0.05 Electricity Table 6. Fuel costs for 2011 (SEAI, 2012) j. The annual savings due to implementation of levels A to D of the upgrade for all heating systems is calculated as the difference between the cost of heating bills for the original house and the sum of the costs of delivered energy and loan payments for the refurbishment options. They are summarized in section The social performance in the energy efficient retrofit covers the occupant s satisfaction with the indoor environment, the user friendliness of service systems and responsible sourcing. The choice of natural materials for the building fabric upgrade can be also included here as the decision of their use would be guided by the social rather than economical factor. Possible implications of each upgrade option are discussed in Chapter 6. The influence of the qualitative social factors is difficult to compare and evaluate but they can be taken into consideration individually when making decision on the upgrade option. 14

28 5 Refurbishment strategies optimal measure choice and calculation results Xing at al. (2011) established a sequential approach in retrofitting existing buildings to achieve zero carbon building, which they called a hierarchical pathway. The authors stressed the importance of reducing energy demand by retrofitting building fabric as a first step. The second stage includes installing energy efficient equipment, and the last - establishing onsite energy supply systems that can be connected to grid and appropriately controlled. This view is taken as a general approach for housing refurbishment strategies (Jenkins at al., 2012, Konstantinou and Knaack, 2011, Feist at al., 2007). In this chapter, such a hierarchical pathway focused on measures closely connected with the building envelope is studied for a case study of an existing house in Dublin. First, the existing house condition is presented for comparison purposes. The first stage of improvements covers measures aiming at space heating demand reduction. Building fabric refurbishment measures consists of floor, walls and roof insulation, windows and doors replacement and the air-tightness strategy for reducing the heat losses and modifications to internal, and window layout for increasing the solar gains. The last measure aiming to reduce the space heating demand is a high efficiency ventilation system. Second stage includes a choice of high efficiency heating system, which enables further reductions in the space heating requirements and provides efficient water heating. The possible renewable technologies aiming at reducing CO 2 emissions due to heating loads are solar thermal panels for the water heating and biomass boilers and heat pumps for space heating. Electrical loads should also be lowered by implementing low energy electrical appliances and behavioural changes. Additionally, PV panels can be installed to reduce the grid electricity demand and further decrease CO 2 emissions connected with producing power. However as these issues are not integrated in the building envelope they are outside of the scope of this work. 5.1 Existing conditions a case study dwelling The best improvements can be achieved in buildings with the worst energy performance as the impact of upgrades will be the most evident. It also makes the most financial sense to invest in a house without any significant upgrades. To allow for a comparison between the different combinations of refurbishment measures a typical semi-detached house was selected that represents one of the common types of Dublin houses among those with the worst energy performance. It is proposed to use a house type that does not pose any issues related to historical listed buildings as this provides opportunity to investigate the possible extent of the deep retrofit techniques. The case study house is an actual building located at no. 58 Cedarmount Road, Mount Merrion, Co. Dublin. It has been a subject of an energy efficient retrofit and extension project the author worked on in 2011 and thus its details are readily available. It is a 3 bedroom, semi detached dwelling built in 1960 s with a suspended, uninsulated and unsealed timber floor, hollow block single leaf walls and no insulation in the roof area. The windows are single glazed with metal frames and the only modernization that was made to the house after it was built was the central gas heating with radiators and a 78% efficient gas boiler. There are two open fireplaces that are still in use on the ground floor and two temporarily blocked chimneys on upper floor. The natural ventilation system consists of four open vents, one in each room with a fireplace. There are no extract fans in bathroom and kitchen. 15

29 The specific space heating demand of the house is 394 kwh/m 2 /y and primary energy demand is 708 kwh/m 2 /y calculated with PHPP. The exact specification, assumptions for PHPP calculations and details of heat losses and gains can be found in Appendix D. Figure 2. Case study house existing plans Figure 3. Case study house existing elevations 16

30 The house has a standard, repeatable plan (Fig. 2). No consideration was given to its orientation, with the north-west (rear) windows having larger area than the south east ones at front (Fig. 3). 5.2 Building fabric refurbishment and ventilation reducing space heating demand The building fabric refurbishment measures are chosen specifically for the case study house type. For floors, walls, roof insulation, windows replacement and air tightness upgrade four levels of refurbishment are proposed depending on its complexity and cost of installation, resulting in different levels of energy savings. One optimal solution is proposed for the layout changes aiming at increasing the solar gains, but it provides different results when combined with the different insulation levels. There are also four ventilation strategies chosen to suit each level of building fabric upgrades. Calculations at the end of each section show the possible energy savings connected with each level. For floor, walls and roof insulation and windows upgrade, the accumulated space heating energy savings are a sum of all the single elements. On the other hand, the air tightness, internal layout changes and ventilation measures have to be applied after all the building fabric measures to provide reliable results showing the energy savings. The sections below follow these guidelines Floor insulation The U-value of the uninsulated and unsealed existing suspended timber floor is 0.68 W/m 2 K. It is a serious source of draughts from between the floor boards, behind the skirtings and around all the penetration holes. There are two options available for upgrading a suspended timber floor: adding insulation and air tightness to an existing structure or replacing it with insulated concrete floor and both are discussed below. a. Upgrading existing timber floor In the case study house the space available for insulation between the existing joists is limited to 110mm (insulation should not be installed below the joists to keep the original ventilation void). For this depth, the U-value of 0.18 W/m 2 K could be achieved for rigid phenolic insulation with thermal conductivity of W/mK. However, even though it provides the best U-value, its application between timber joists poses a risk of water condensation in timber structural elements, as explained in Appendix F. For that reason it should be avoided in this application. The least expensive and easy to install material would be the mineral wool (thermal conductivity of 0.04 W/mK) that would achieve U=0.26 W/m 2 K. However, it is fully permeable, so its installation does not address the air tightness in any way. The most effective material suitable for the floor application is open cell sprayed foam. Once it is installed after all the elements penetrating the floor are in place, the expanded foam fills all the gaps and both insulate and seal the floor. With thermal conductivity of W/mK it provides a U-value of 0.24 W/m 2 K. To add air tight layer to upgraded timber floor, EST (2011) recommends replacing the old floorboards with chipboard and ensure sealing all the joints. 17

31 Figure 4. Existing suspended timber floor insulation. Adapted from: EST (2011) b. Replacing existing floor with insulated concrete floor The removal of existing timber floor and replacing it with new concrete structure gives an opportunity to install more insulation and a new damp proof membrane (DPM) to achieve very good air tightness. It is important to maintain the continuity of insulation between wall and floor. Insulation can be placed above the concrete floor in case of internal wall insulation and when a low thermal mass is preferred (Fig. 5). The influence of thermal mass is discussed in Appendix G. Insulation below the concrete is better suited if an under floor heating system is planned (the pipes can be installed in upper part of the slab) or when a high thermal mass is desired. In that case a layer of insulation should be installed between the concrete slab and rising wall to minimize thermal bridge (Fig.6). A DPM playing a role of air tightness barrier should be installed under the insulation, lapped up the wall and sealed in case of both solutions. In the case study house, the depth from the finished floor level to existing floor sand blinding is 300mm. The necessary floor finish and concrete slab should be 130mm, so the following U-values could be achieved assuming 170mm of insulation is added on top of the existing sand blinding: - U =0.17 W/m 2 K for white polystyrene insulation, λ = 0.04 W/mK; - U =0.11 W/m 2 K for phenolic insulation, λ =0.022 W/mK. In case of a removal of the existing sand blinding, any thermal transmittance can be achieved, for example 300mm of grey polystyrene insulation provides a U-value of 0.09 W/m 2 K. All U-value calculations can be found in Appendix H. 18

32 Figure 5. Existing suspended timber floor replaced by concrete floor with insulation above the slab. Adapted from: Energy Saving Trust (2011) Figure 6. Existing suspended timber floor replaced by concrete floor with insulation below the slab. Adapted from: Energy Saving Trust (2011) c. Calculations Table 7 shows a comparison of four chosen options for the floor insulation. Option A includes installation of the 110mm open cell foam spray between the existing timber joists, as it provides the simplest and least expensive solution that allows improving the air tightness in timber floor. Its cost consists of the insulation and new chipboard installation. For the improved U-value all other options involve removing the existing timbers and installation of DPM, new concrete slab, insulation and screed. Options B and C assume the existing sand blinding is left in place, so that a 170mm layer of insulation can be installed, but different insulation materials are used: less expensive white polystyrene in option B and better performing, but more expensive phenolic rigid insulation in option 19

33 C. Option D includes removing the existing sand blinding and installation of 300mm of the less expensive polystyrene. All U-value calculations (column 1) are shown in Appendix H. The specific space heating demand of the house (column 2) is calculated with PHPP. The specification and assumptions for the existing house calculations (baseline) can be found in Appendix D. The calculations for options A to D are derived from the baseline settings, with the U-value of the upgraded element changed according to column 1. The saved energy (column 3) is a difference between the baseline performance and upgraded heating energy. The capital cost (column 4) is estimated from the quotes for similar projects conducted by the author during 2011 and from supplier price lists published online (the calculations can be found in Appendix E). Columns 5 and 6 indicate the costs and energy savings per meter square of the house. This method applies to all calculations of refurbishment options in section 5.2. (1) (2) (3) (4) (5) (6) U-value [W/ m 2 /K] Heating Energy [kwh/m 2 /y] Saved energy [kwh/m 2 /y] Capital Cost Cost/TFA [ /m 2 ] Saved kwh/ m 2 /y per 1 A B C D Baseline - suspended timber, no insulation 110mm sprayed foam between the joists 170mm white polystyrene + 100mm concrete floor 170mm phenolic + 100mm concrete floor 300mm grey polystyrene + 100mm concrete floor , , , , Table 7. Floor refurbishment options Wall Insulation The case study single leaf wall can either be insulated internally or externally, both options are described below and more discussions on their advantages and disadvantages are provided in Appendix I. a. Internal insulation The most common internal insulation material is currently a rigid insulation board a layer of phenolic insulation with attached plasterboard. The boards are either fixed to the wall using adhesive and mechanical fixings, or nailed to 25mm softwood battens. The vapour control is built in the system in the form of a foil at the back of the boards. Another approach includes installing insulation between the timber battens fitted to the wall and applying a vapour control membrane followed by the plasterboard. Mineral wool was used in the past, but currently it is recognized that it is not the best solution for vertical insulation as it is prone to sagging and collapsing when in contact with moisture. Natural materials, such as hemp wool or woodfibre boards can be used more successfully, although they are more expensive. However, such installation would require about twice as much 20

34 depth of the insulation comparing to the phenolic insulated plasterboard (thermal conductivity of woodfibre is 0.04 W/mK, comparing to 0.02 W/mK for rigid phenolic board). The necessary vapour membrane can act as an air tightness barrier, but its installation in a continuous layer proves to be problematic, as explained in Appendix I. Figure 7. Section through internally insulated external wall b. External insulation External Wall Insulation (EWI) systems consist of an insulation layer, fixed to the external surface of the wall, followed by a reinforcing mesh and a finish render or cladding. Wet render systems have either a thick sand-cement render applied over a wire mesh, or a thinner polymer based render applied to a lighter glass reinforced mesh (EST, 2011). The dry systems use cladding systems as a finish (timber panels, stone or clay tiles etc.) There is a number of different insulation types used, but the most common for standard application (and cost effective) is the expanded polystyrene (EPS) with thermal conductivity of 0.04W/mK for standard white boards and W/mK for enhanced 21

35 grey ones. If the thickness of insulation is an issue, phenolic insulation can be used with thermal conductivity of 0.02W/mK. In case of masonry with moisture issues the best application would be mineral wool or natural materials with ability to transfer the moisture to outside. Fig. 8 shows a typical external insulation application. Figure 8. Section through externally insulated external wall Installation of external insulation enhances the air tightness of the building, but additional measures are required to achieve the highest levels. This can be achieved by either installing sealed membranes and plasterboard, or internally plastering all external walls (or repairing existing plaster). The latter is easier and preferable for retaining the high thermal mass of the construction (discussion on thermal mass effects is provided in Appendix G). It is necessary to pay attention to careful application of a continuous layer of plaster. Difficult places include area between the joists in the depth of intermediate floor or narrow gap between the last joists along the wall. Where the plaster cannot be installed, open cell foam insulation can be applied or the joists can be taped to the wall. 22

36 c. Calculations Table 8 shows a comparison of four installations. The performance and cost per square meter of each level takes into account the influence of thermal bridges associated with each application (the calculations for U-values can be found in Appendix H). The choice of options is based on discussions from Appendix I. Option A is an internal insulation with 80mm of woodfibre insulation, breathable membrane and a 25mm service cavity filled with cellulose insulation, finished with plasterboard. Options B to D include different thicknesses of grey polystyrene external insulation. (1) (2) (3) (4) (5) (6) A B C D Baseline - no insulation 80mm woodfibre + 20mm callulose in service cavity 150mm grey polystyrene external insulation 200mm grey polystyrene external insulation 300mm grey polystyrene external insulation U-value [W/ m 2 /K] Heating Energy [kwh/ m 2 /y] Saved energy [kwh/ m 2 /y] Capital Cost Cost/TFA [ /m 2 ] Saved kwh/ m 2 /y per , , , , Table 8. Wall refurbishment options Roof insulation It is commonly recognized that the insulation at attic floor is generally the easiest and the most costeffective way for roof insulation. Rafter insulation should be considered only if the attic space is habitable, otherwise the whole attic would be unnecessarily heated. In the case study house the attic space is limited with its hipped end, so it is assumed it will not be adapted. Thus the ceiling insulation is the best solution. a. Insulation at attic floor Insulating between the joists can bring the U-value of the ceiling to about 0.4W/m 2 K with the material s thermal conductivity of 0.04W/mK and additional layers can be installed on top. Insulation should not be squeezed, so if it is not rigid and the attic is going to be used as a storage space, the floor needs to be raised. This usually requires counter joists installed across original ones with insulation between them and decking boards on top. Attic space ventilation ensures that condensation does not occur, so the vapour control is not necessary (Fig.9). However, it is also important to provide an air tight barrier at the ceiling level. When using traditional insulating materials, like mineral wool, an air tight membrane can be installed under the timber joists. To facilitate this, the existing ceiling plasterboard needs to be replaced. Also 23

37 all penetrations (cables etc.) need to be carefully sealed. Another, simpler approach is to install the open cell spray foam insulation from above, leaving the existing plasterboard in place. This would have to be done once all the wiring is in place and the cables should be extended above the insulation in the attic. The foam would seal all the openings, make the ceiling air tight and provide insulation in the same time. It is more expensive than other more traditional materials, but eliminates work related to installing the membrane and new plasterboard. Also, when sprayed between the joists, it does not necessarily require installation of flooring boards for storage purposes. A closed cell, non breathable insulation materials like phenolic board are more difficult to deal with, as explained in Appendix F and should be avoided if possible. Figure 9. Thermal bridge at wall ceiling junction A. Insulation between existing rafters B. Part of the roof raised Figure 10. Wall ceiling junction thermal bridge reduced 24

38 Adding insulation at ceiling in the existing geometry of joists and rafters is creating a thermal bridge at the wall plate (Fig.9). It can be partially mitigated by installing insulation in the rafter space at the junction of wall and ceiling floor. If an existing old non-breathable felt is left in place a ventilation cavity would need to be created. Additional insulation could also be added internally at the wall to ceiling junction (Fig.10A), or a part of the roof could be raised to accommodate more insulation in the rafter space (Fig.10B). The simplest method of dealing with recessed light fittings would be to eliminate them completely in the first floor ceiling, but if they are necessary the air tightness barrier should be created above the fixture enclosure. b. Calculations The simplest upgrade in option A involves installing 100mm of spray foam directly between the existing joists and about 50mm between rafters at wall plate. The associated cost covers installation of insulation only. Option B shows calculations for additional 200mm of sprayed foam between added counter-joists and the same 50mm at wall plate (Fig.10A). Additional cost includes installation of counter joist timbers and more insulation. In option C the wall plate area is additionally insulated with 150mm of sprayed foam in the raised section of roof (Fig.10B). Extra work involves removing and re-fitting the bottom layers of roof tiles and replacing that part of the membrane. Option D adds an additional 100mm of insulation on the floor. The U-value calculations take into account the poorer performance of wall plate area and can be found in Appendix H. The cost of new soffit and fascias is not included in calculations below as they are not directly connected with thermal upgrade. (1) (2) (3) (4) (5) (6) A B C D U-value [W/ m 2 /K] Heating Energy [kwh/ m 2 /y] Base - no insulation mm spray between joists, 50mm between rafters at wall plate 100mm spray between joists + 200mm above joists, 50mm between rafters at wall plate 100mm spray between joists + 200mm above joists, 150mm between rafters at wall plate 100mm spray between joists + 300mm above joists, 150mm between rafters at wall plate Saved energy [kwh/ m 2 /y] Capital Cost Cost/TFA [ /m 2 ] Saved kwh/ m 2 /y per , , , Table 9. Ceiling refurbishment options 25

39 5.2.4 Windows and doors replacement Correctly installed energy efficient windows not only reduce the use of energy in the house due to smaller heat losses and greater solar gains, but also improve occupants thermal comfort (Feist, no date). The performance of a window is determined by: a. U-value and the solar transmittance of the glazing, which is influenced by the number of panes (two or three), width of the gap between them, low-e coatings helping to reflect the heat back to the house, the gas filling the gap and level of iron content in glass, as it influences light and solar transmittance (EST, 2011); b. U-value of the frames, which depends on the material they are made of and its insulation. It is important the frame size is as small as possible, as it always has bigger thermal transmittance then the glazing; c. The performance of the spacer spacer thermal bridge should be minimized; d. The performance of the installation to achieve the lowest thermal bridge, windows should be fitted in the depth of the insulation (Fig. 11). Figure 11. Window installation with minimised thermal bridge Window frames can be manufactured from different materials. Current most common options include PVC, timber and aluminium-clad timber frames. Austrian Institute for Healthy and Ecological Building (2009) rated windows looking at their primary energy content, global warming potential, disposal and utilization potential and maintenance evaluation. Discussion on the performance of all the options can be found in Appendix J. b. Calculations It is proposed to use timber and alu-clad timber windows to eliminate the worst performing environmentally PVC option, as explained in Appendix J. Each option s U and g-values are described in Table 10 in detail. The costs includes an installation with a minimal Ψ=0.009W/mK, according to Fig.11. Table 10 shows the same results in columns 1-6 for the overall house s performance changes as in tables 5-7 above, but has additional columns 7 and 8 outlining the specific performance of the window options. Column 7 presents the window s heat losses and column 8 shows how much energy is gained due to solar energy. The balance between losses and gains explain why the higher upgrade levels are beneficial. When it comes to the door replacement, the well insulated examples can currently achieve a U-value of 0.8W/m 2 K, a significant improvement over solid timber doors with a U- value of about 3.0W/m 2 K. 26

40 A B C D Base - metal, no thermal break, single glazing, g=0.87 timber, double glazing (Ug=1.1, Uf=1.0, g=0.64, Ψ spacer =0.14); doors U=1.4 timber, triple glazing (Ug=0.6, Uf=1.0, g=0.54, Ψ spacer =0.14); doors U=1.2 alu-clad, triple glazing (Ug=0.6, Uf=1.0, g=0.54, Ψ spacer =0.14); doors U=1.2 alu-clad, triple glazing, Passivehaus certified (Ug=0.53, Uf=0.75, g=0.55, Ψ spacer =0.027); doors U=0.8 (1) (2) (3) (4) (5) (6) (7) (8) U- value [W/ m 2 /K] Heating Energy [kwh/ m 2 /y] Saved energy [kwh/ m 2 /y] Capital Cost Cost/TFA [ /m 2 ] Saved kwh/ m 2 /y per 1 Transmis -sion Losses [kwh/ m 2 /y] Solar Gains kwh/ m 2 /y , , , , Ug=U-value of glazing Uf= U-value of frame g= solar transmittance Ψ spacer =thermal bridge of the spacer Table 10. Window replacement options As can be seen in column 6 the biggest savings in kwh/m 2 /y per each Euro invested is brought by the double glazing in Level A when looking at energy savings comparing to the original house performance. However, the net heat gains delivered by windows are only possible with triple glazing (options B to C), as shown in columns 7 and 8. The biggest net gain is achieved by the Passivhaus certified window (option D) and comparing to option C, its higher costs is recovered by bigger energy savings. 27

41 5.2.5 Combined building fabric savings Air tightness strategy depends on the chosen type of insulation, so it always has to be considered simultaneously with the insulation strategy for each element. This is why the cumulated effect of floor, wall and roof insulation and windows replacement was calculated first. The results are shown in Table 11. Column 1 shows the energy needed for space heating for each level of upgrade. Column 2 presents accumulated energy savings calculated as a sum of the previously calculated in PHPP savings from the four implemented measures. The total cost of those four measures is summarized in column 3, the costs per meter square of the house can be found in column 4 and saved energy per m 2 per year for one Euro spent in column 5. Level of combined floor, walls and roof insulation and windows upgrade (1) (2) (3) (4) (5) Heating Energy [kwh/m2/y] Saved energy [kwh/m2/y] Cost of all measures Cost/TFA m 2 [ /m2] Saved kwh/m2/y per 1 Baseline 394 A , B , C , D , Air tightness a. Air tightness measures Table 11. Combined effect of building fabric upgrade options Air leakage leads to draughts and discomfort as the replacement air coming from outside is cold and to heat losses as it needs to be reheated. It has also been recognized that air leakage is not a suitable mean for ventilation, as it is impossible to control its air flows. That is why introducing air tightness is an integral part of a retrofit. It requires a strategy for the whole house and the simpler it is, the easier it can be executed on site (for example choosing the wet plaster approach is safer than using membranes and tapes on external walls). Most commonly the air tight layer is located on the internal side of exterior fabric elements, as discussed in sections above. The most vulnerable points of the air tightness layer are the joints between different elements and any penetrations. Fig. 7 and 8 show a possible approach to treating all the joints: they can be taped over or sprayed with expandable foams. Simple measures helping to limit breaking the air tightness layer include avoiding electrical fittings on external walls and recessed lights in 1 floor ceiling, whenever possible. b. Calculations additional air tightness measures Table 12 shows possible to achieve air tightness strategies associated with earlier described four upgrade levels. All the options include removing of the existing chimneys, as they will not be used and would be a source of air permeability difficult to deal with. In option A air tightness strategy integrated in fabric upgrade includes sprayed foam insulation in existing timber floor, internal wall insulation with vapour control, sprayed insulation in ceiling and double glazed timber windows. Additional air tightness measures allowing upgrading the house s air permeability to 5m 3 /m 2 /h 28

42 consist of: taping between floor chipboard and wall membranes, around existing 1 floor joists and windows and between the wall membrane and ceiling. In options B, C and D fabric upgrade involves installation of new concrete floor with DPM, external wall insulation and sprayed foam insulation in the ceiling (the difference between the options is the depth of insulation). The additional air tightness measures ensuring achieving better results in air tightness test include application of wet plaster on external walls and taping between all the joints: between DPM and wall, around 1 floor joists and windows and between walls and ceiling plasterboard. Column 1 presents the accumulated heating energy use for combinations of fabric elements upgrade summarized in Table 11. Column 2 shows the heating energy use improved after installation of additional air tightness measures resulting in assumed improved air tightness test results: 5.3 ac/h for level A, 3.2 ac/h for level B, 1.0 ac/h for level C and 0.6 ac/h for Level D. Level of upgrade A level for fabric (1) + airtigness at 5 m 3 /m 2 /h (5.3 ac/h) (2) B level for fabric (1) + airtigness at 3 m 3 /m 2 /h (3.17 ac/h) (2) (1) (2) (3) (4) (5) (6) Heating Energy (1) [kwh/m 2 /y] Heating Energy (2) [kwh/m 2 /y] Saved energy [kwh/m 2 /y] Capital Cost Cost/TFA [ /m 2 ] Saved kwh/m 2 /y per , , C level for fabric (1) + airtigness at 0.95 m 3 /m 2 /h (1.0 ac/h) (2) D level for fabric (1) + airtigness at 0.57 m 3 /m 2 /h (0.6 ac/h) (2) , , Table 12. Combinations of fabric upgrade options and air tightness measures Layout and windows modification improving solar gains a. Direct solar gains The calculations for a re-design of internal layout and window openings, implementing solar energy design should be done after minimising all heat losses (Kwok and Grondzik, 2011). The general rules describing direct solar gain strategies can be found in Appendix K. Implementing direct gain principles in the case study house included enlarging of the front window openings from 20% to 46.6% of the front wall area. It was the maximum feasible change considering the existing streetscape. The area of north-west windows was reduced from 24.7 % to 16.6% (the minimum for daylight requirements), while the north-east windows were retained at low 4% (Fig. 12). Internal layout changes included removing most of internal partition walls on ground floor to allow for free flow of light and more even distribution of solar heat. The revised layout also provides a more spacious living area within the original external walls. The proposed new window size and location not only decreases heating energy use, but also provides better distribution of the light and access to the garden from the living space. The area of thermal mass required to store the solar heat can be 29

43 estimated by a general rule, as explained in Appendix K (thermal massive elements are marked on Fig.13). Figure 12. Changes in windows layout that allow maximising direct solar gains Figure 13. Changes in plan layout that allow maximising direct solar gains 30

44 b. Calculations When it comes to refurbishment projects, the solar design implementation is restricted by existing conditions. However, substantial heat gains can still be achieved with the use of available passive solar techniques, as shown in Table 13. Changing the size and layout of windows and improving internal layout allowing for better use of natural light could also bring savings in energy spend on lighting and improve indoor environment. The cost involved in the reconfiguration of internal walls and window openings could not be justified just by the heating energy savings, but the most important benefit involves the improved living conditions. That is why for the purpose of this calculation the energy savings are treated as an extra feature that does not incur any costs. Column 1 of Table 13 shows the energy required for heating after implementing all the previous upgrades (carried out from column 2 of Table 12). Column 2 presents the improved heating energy after implementing changes in internal layout described above (the changes are the same for each level). Level of upgrade (1) (2) (3) Heating Energy for original layout [kwh/m2/y] Heating Energy for revised layout [kwh/m2/y] Saved energy [kwh/m2/y] A B C D Table 13. Possible energy savings for each upgrade level due to increased solar gains Ventilation strategy a. Ventilation systems The role of ventilation is removing pollutants, regulating humidity and providing the occupants with sufficient fresh air. Since most of the existing sources of uncontrolled ventilation are removed in the retrofit situation due to increased air tightness, a new strategy is required to provide sufficient ventilation levels. Two factors will contribute to the energy efficiency of the new ventilation system: ventilation heat losses and energy used for running the system. Typically the natural systems contribute to greater heat losses, but use little or no energy for running, whereas mechanical systems control the fresh air intake, thereby limiting heat losses, but they are using considerable amount of power to achieve this. Natural systems do not provide control over the ventilation rates, so they are unpredictable and if not properly controlled manually by occupants can lead either to large heat losses or inefficient air quality and problems with dampness. Mechanical systems provide more control, provided that they are operated according to how they were designed. The main types of natural and mechanical ventilation systems that can be used in retrofitted dwellings are described in Appendix L. 31

45 b. Calculations Since the performance of ventilation system is directly connected with the air tightness level of the building, the following systems were chosen to match the relevant upgrade level (based on the Appendix L discussion): - Level A: intelligent passive stack natural ventilation (ipsv) with non electrical humidity-sensitive control extract grilles and air inlets; - Level B: demand control mechanical extract ventilation with humidity controlled extract fan and air inlets; - Levels C and D: whole house balanced mechanical ventilation with heat recovery with humidity controlled fan that is recovering heat from exhaust air. Table 14 shows further space heating energy savings. Column 1 presents the accumulated improved space heating energy after installation of building fabric measures. Column 2 shows heating energy after installing new ventilation systems as discussed above. (1) (2) (3) (4) (5) Heating Energy (1) [kwh/m 2 /y] Heating Energy (2) [kwh/m 2 /y] Saved energy [kwh/m 2 /y] Capital Cost Power use [kwh/m 2 /y] A level + ipsv B level + DCMV , C level + MVHR , D level + MVHR , Summary Table 14. Energy savings for different upgrade levels Table 15 summarizes upgrades connected with the space heating demand reduction. Space Heating Energy Level A [kwh/m 2 /y] Space Heating Energy Level B [kwh/m 2 /y] Space Heating Energy Level C [kwh/m 2 /y] Space Heating Energy Level D [kwh/m 2 /y] 1 Baseline Floor insulation Wall insulation Roof insulation Wind. + Doors Air tightness Solar gains Ventilation Table 15. Accumulation of space heating energy savings for each upgrade level 32

46 Table 15 shows the accumulated space heating energy savings. The installation of building fabric upgrades (rows 2 to 7) provides a 78% improvement in the space heating energy use for Level A, 85% for Level B, 87% for Level C and 90% for Level D comparing to the original house s performance. The final improvement in the space heating energy use after implementing the proposed ventilation systems brings the results up to 82% for Level A, 92% for Level B, 97% for Level C and 99% for Level D comparing to the original house s performance. The final space heating energy after ventilation system improvements added is almost 93% smaller for Level D than for Level A of the upgrades, a much bigger difference than for the building fabric improvements alone. Level D of the upgrades provides a significant improvement, reducing the space heating requirement almost to zero. However, it has to be noted that these improvements do not take into account the energy used for running the ventilation system and the final balance needs to be taken into account as well. 5.3 Energy efficient equipment reducing space and water heating energy use With the reduced space heating use, the hot water preparation becomes the main part of energy required for heating. Once the space and water heating demand is reduced as much as possible, the increased heating system s efficiency provides the final cut in energy delivered to the house. These two issues are discussed below Water heating The hot water energy demand should be reduced similarly as in the case of the space heating. The possible measures include features like shower heads reducing the use of hot water etc., but in this case a much more important aspect is the occupant s behaviour. It would be valuable to investigate the possible energy savings possible to achieve in this area. Unfortunately, this is not in the scope of this study. Instead, the average hot water demand is estimated, based on the assumed occupant s usage. It is summarized for the case study house family in Table 16. Water usage /2 adults + 2 children no/day L L/day Washing up Shower (adults, once a day) Bath (children every second day) Bath (adults, once a week) Sink (hands washing) Sink (evening washing) Daily consumption (L) 129 Daily consumption/ person 32 Table 16. Average daily hot water usage The default PHPP value of 25L/person/day would suggest implementation of more rigorous hot water saving strategies, the proposed by DEAP 40L/person/day on the other hand seems excessive. It can be assumed that 32L is a viable average. The useful heat required for preparing the required hot water demand is 2710 kwh/y, calculated in PHPP. The total heat demand of the DHW system depends on the distribution and storage insulation and it is discussed in section 5.3.2b. 33

47 5.3.2 Fossil fuel heating systems The heating system s type and output needs to be adjusted, taking into consideration the extent of the fabric improvement. Since the case study house has an existing gas connection, a new efficient gas boiler would be the simplest solution for the fossil fuel heating system. Other options for renewable sources of heat are discussed in the next section. Two types of gas boilers are available: a regular and combi systems. a. Space heating distribution options Radiators or underfloor (UF) heating can be used for distribution of space heating. It is common to combine UF heating on the ground floor with radiators upstairs (piping for UF heating can be easily installed in the new concrete ground floor, freeing walls from radiators) because of the expected better occupant s thermal comfort due to more even distribution of heat. Drawbacks of UF include lower responsiveness of the heating system, which can be especially concerning when the design is counting on the direct solar gains. The size of new distribution system needs to be calculated so that it provides the required level of heating in the hose with less heat losses. Radiators or UF system may even not be necessary if the ventilation system with heat recovery is installed and is capable of distributing the required heat loads. The system also needs adequate control and responsiveness to external conditions. The boiler and pump must react automatically when there is no demand for heat. The configuration ensuring that is known as a boiler interlock. If there is a requirement of having different temperature in different parts of the house, it should be divided into zones with separate time and temperature controls. Seven day programmable room thermostats are recommended (EST, 2011) as they give the greatest choice of temperature and timing. Water heating should be timed separately. The most efficient use of the heating system is ensured by controls that are easy to use and understand by the occupants. b. Regular gas condensing boiler A regular system produces hot water that is stored in a cylinder. The cold water from mains is first transported to a cold water storage cistern located in the attic, to use gravity to enhance pressure. Table 17 presents the primary heating energy demand (PHED) for the original boiler (column 1) and a new condensing boiler (column 2) for the four levels of upgrades, calculated with PHPP. PHED includes space and water heating energy and auxiliary electricity necessary for running the heating system. The original heating system is a 78% efficient, 30kW gas boiler without heating controls, uninsulated pipes (Ψ=0.64) and hot water cylinder (specific heat loss=7.5 W/K). The proposed new heating system includes a 91% efficient, 8kW regular condensing gas boiler, with heating controls: 3 zoned timer (water heating and 2 space zones), room and hot water cylinder thermostats, 50mm PIR pipes insulation (Ψ =0.14) and hot water cylinder insulation (specific heat loss=2.5w/k). (1) (2) (3) (4) PHED (1) [kwh/m 2 /y] PHED (2) [kwh/m 2 /y] Saved energy [kwh/m 2 /y] Capital Cost Baseline 660 A Level , B Level , C Level , D Level , Table 17. Energy savings due to a boiler upgrade (regular boiler) and its capital cost. 34

48 As can be seen in column 1, the PHED is not decreasing linearly for the higher levels of upgrades. This is due to the hot water heat losses from uninsulated pipes and storage in the ineffective original heating system and the issue is explained in more detail in section 6.1.2a. The PHED for the new heating system (in column 2) is decreasing in a linear way due to smaller hot water losses. However it is not decreasing proportionally to the space heating values. This is because of the rising auxiliary energy for the ventilation systems in higher upgrades and this is also discussed in section c. Combination boiler A combination (combi) boiler heats water directly from the main and the system does not need to store cold and hot water. A type of instantaneous combi boiler has a so called keep hot facility. It keeps hot water within the boiler to reduce the response time at boiler start-up (EST, 2011). Table 18 shows the energy savings for a combi boiler upgrade. The new boiler efficiency, space and water distribution system and controls are the same as for the regular boiler. (1) (2) (3) (4) PHED (1) [kwh/m 2 /y] PHED (2) [kwh/m 2 /y] Saved energy [kwh/m 2 /y] Capital Cost A Level , B Level , C Level , D Level , Table 18. Energy savings due to a boiler upgrade (combi boiler) and its capital cost. The increased savings that can be seen when comparing column 3 of tables 17 and 18 are due to the lack of heat losses from the hot water storage in the combi system Renewable heating a. Biomass boilers Biomass boilers emit considerably less CO 2 than gas boilers. Burning biomass does release CO 2, but this is balanced by the carbon dioxide that was absorbed during the plant s growth. The process is almost carbon neutral, with the only additional emissions associated with planting, harvesting, processing and transportation. Even with these, its emissions are about 90% lower compared to the burning of fossil fuels (EST, 2011). This is reflected in the PHPP methodology which uses the primary energy factor of 0.2 for any wood fuels comparing to 1.1 for gas. Modern stoves and boilers have efficiencies in the range of 90%-95% and can be successfully controlled. Disadvantages of biomass include the storage space required for the fuel, the need for feeding the appliance (in the absence of a hopper, used for bigger applications) and removal of the ash residue. Biomass boilers may be suitable for larger single dwellings or for example for two semi detached houses, where a greater heating capacity is required. A stove would be a better choice for small application, such as the case study house. For well insulated dwelling it can provide the entire heating demand and can also be connected to the hot water cylinder to supply or augment the hot water supply. 35

49 For this case study house it is considered there wouldn t be enough space for a larger hopper fed boiler, but a manually fed stove could be installed provided the occupants would not mind the associated maintenance. Table 19 shows a difference in PHED calculated in PHPP between the original gas boiler with 78% efficiency (column 1) and a biomass stove, 95% efficient for all 4 levels of the upgrade. The distribution systems, hot water storage and controls are the same as for the regular gas boiler option in section 5.3.2b. (1) (2) (3) (4) PED (1) [kwh/m 2 /y] PED (2) [kwh/m 2 /y] Saved energy [kwh/m 2 /y] Capital Cost A Level , B Level , C Level , D Level , Table 19. Energy savings due to a biomass boiler upgrade and its capital cost. The very low energy use for biomass boiler reflects the use of factor 0.2 between the delivered energy and final primary energy comparing with the 1.1 factor for gas boilers. b. Solar thermal panels Solar thermal hot water systems are most efficient in providing Domestic Hot Water (DHW). The panels in the form of a flat plate or evacuated tube absorb sun radiation. The heat is then transferred (usually by an antifreeze liquid) to the hot water storage through an additional coil in the cylinder. The amount of heat collected depends on the panel s size and type, angle of its position, existence of shading, the geographic location and also the size of tank (EST, 2011). During summer the system can satisfy about 80% of DHW demand, and during the year 40% - 60% depending on the size of panels. An auxiliary heat source will be required to ensure that the water is heated to a required temperature at all times. Table 20 presents energy saved by the use of solar panels, calculated in RETScreen (Natural Resources Canada, 2012) (1) (2) (3) (4) (5) 3.74m 2 evacuated tube panels + 200L cylinder 4.675m 2 evacuated tube panels + 250L cylinder 5.61m 2 evacuated tube panels + 300L cylinder Hot water demand [kwh/y] Solar heating delivered [kwh/y] Saved energy [kwh/m 2 /y] Solar heating delivered % Capital Cost % 4, % 4, % 5, Table 20. Energy savings due to solar water heating installation and its capital cost. 36

50 The above energy saving calculation assumes that all available heat will be utilized. However, a lot depends on the occupants behaviour as well. A study by Hill at al (2011) showed that a 65% of surveyed solar hot water installation users do not utilize its full energy savings potential by programming the boilers to top up the water heating in the morning. If the water is heated before the systems starts working, it can t be heated even if there is sun available. The calculations for larger households (similar in size to the case study water usage) showed that the potential energy savings from solar thermal system of 56% can drop to 42% if the boiler is used both in evening and in the morning. Thus it is very important that the occupants know how to use the system in the most efficient manner. c. Heat pumps The heat pump can use ground or air as a heat source. Ground pumps are more efficient as they operate on a depth with a constant temperature of about C. However, they require a reasonably large site for installation of the heat exchanger, so they are not considered appropriate for a semi-detached house situation. Air source heat pumps (ASHP) concentrate the heat of the outside air, so with the lower temperatures in winter they are less efficient. However, they are also easier to install and less expensive. Table 21 shows the possible energy savings of the typical application and its cost for the four levels of upgrade. (1) (2) (3) (4) PED (1) [kwh/m 2 /y] PED (2) [kwh/m 2 /y] Saved energy [kwh/m 2 /y] Capital Cost A Level , B Level , C Level , D Level , Table 21. Energy savings due to a heat pump upgrade and its capital cost. Heat pumps are capable of providing only low temperatures, so it is more efficient to use low temperatures for heating, such as under floor heating and low temperature radiators. The typical efficiency of an ASHP is %, but can be up to 500% on more recent units in comparison to direct electric heating. The improvement compared to a highly efficient gas boiler is much lower, because grid electricity is more carbon-intensive than gas (for DEAP calculations the electricity factor is 2.58 and gas: 1.1). If the heat pump s power source is topped up by a low-carbon source like solar PV, then a further reduction in CO 2 emissions can be achieved. 37

51 5.3.4 Summary of the heating systems options Table 22 summarizes the primary energy for heating savings possible to achieve with different heating system upgrades. Renewable heating options save more energy than the gas boilers and the biomass boiler achieves the best result. PHED Regular Gas PHED Combi Gas PHED Heat Pump PHED Biomass A Level 77% 78% 84% 95% B Level 83% 85% 88% 96% C Level 86% 88% 90% 96% D Level 86% 89% 91% 96% Table 22. Energy savings in Primary Heating Energy Demand due to the different heating system upgrade options. 38

52 6 Analysis results In this chapter, the building fabric, ventilation and heating upgrade options described and preliminarily evaluated in Chapter 5 are analysed in the light of environmental, economical and social factors, as set out in Chapter Environmental impact Environmental impact of the refurbishment measures focuses on the reduction of CO 2 emissions, as discussed in section In section savings due to the reduced energy demand for space heating are discussed for proposed building fabric refurbishment measures. Section analyses CO 2 emissions that can be avoided due to reduced energy use by more efficient heating systems for both space and water heating. Regular and combination gas boilers are compared to biomass boiler and heat pump, with an option of solar thermal heating for each boiler type system. Here the amount of emissions is influenced by lower energy use caused by increased efficiency of systems and also by the type of fuel Annual CO 2 savings due to reduced energy use for space heating Figure 14. Annual CO2 emission savings for Levels A, B, C and D. 39

53 Regarding the building fabric refurbishment, the CO 2 savings relate only to energy used for space heating, so this section excludes energy used for water heating. Savings of CO 2 emissions from gas due to space heating (SH) and auxiliary electricity (AE) per each upgrade measure are shown in Fig.14 for each refurbishment level, calculated as set out in section 4.2.1a. Level A offers overall cut in CO 2 emissions of 78.7%: from the baseline of 8.7 tco 2 /y to 1.9 tco 2 /y, level B cuts them to 1.1 tco 2 /y providing 86.9% savings, level C to 0.9 tco 2 /y, with 89.6% savings and level D achieves 0.7 tco 2 /y, with 92% savings in CO 2 emissions Annual CO 2 savings due to improved efficiency of heating system and different fuel options for Levels A to D The calculations from section give information on the CO 2 savings from reduced space heating requirements due to building fabric improvements that can provide guidance for choosing required level of refurbishment. However, only the choice of the heating system in conjunction with the fabric upgrade level provides a full picture of achievable savings. As shown in next subsections, the water heating energy demand becomes not only more important, but also raises with the decreased space heating demand, becoming a dominant energy consumer in the low energy house. The calculations below show CO 2 levels for both space and water heating after installation of new gas boiler, biomass boiler and heat pump in conjunction with the four previously discussed fabric upgrade levels and compare them with the original heating system performance. a. Summary of annual CO 2 emissions for the original gas boiler First, for the comparison purposes, the annual CO 2 emissions due to Primary Heating Energy (PHE) are established for the original boiler system and four levels of fabric improvements. Table 23 shows a breakdown of PHE elements for the original heating system. It shows CO 2 emissions for gas used by the boiler for water and space heating and also emissions due to electricity use by auxiliary systems (pumps, fans etc.) Insulation Level CO 2 Emissions from DHW Heating CO 2 Emissions from Space Heating CO 2 Emissions from Auxiliary Electricity Total CO 2 Emissions from PHE CO 2 Emission Savings Comparing to Baseline House PHE [%] Baseline A level % B level % C level % D level % Table 23. Breakdown of CO2 emissions components for the original heating system for four levels of building fabric upgrade. It can be noticed that the hot water related CO 2 emissions rise for lower space heating demand (gradually from level A to D). Better insulated houses have shorter heating season, so the hot water pipes heat losses are contribute to the space heating to a smaller degree. The final DHW energy rises because of the bigger net heat losses. In addition to this, water heating becomes more and more substantial part of the energy use with decreasing space heating demand. The increase in CO 2 40

54 emissions due to higher hot water demand is bigger than the saved CO 2 emissions due to smaller space heating demand. Auxiliary energy demand also rises for options B, C and D due to mechanical ventilation electricity usage, despite the fact that the heating systems use less electricity. The rules regarding rising hot water demand and auxiliary electricity CO 2 emissions for higher levels of upgrade apply to all the upgraded heating options described below. The overall CO 2 savings are growing for higher upgrades B and C, because the space heating demand drops faster than the water heating demand rises. However, it goes down for Level D, when that situation reverses. That is why the heating system should be upgraded together with the refurbishment of the building fabric in the deep retrofit situation, including especially important water pipes and hot water insulation. Thus the next sections compare the performance of the new systems with the baseline house performance, to show the achieved CO 2 emissions more clearly. b. Annual CO 2 savings for upgraded system with a regular condensing gas boiler without and with solar thermal heating Table 24 shows CO 2 emission levels for regular condensing gas boiler upgrade (as per section 5.3.2b specification). The last column shows possible savings in total CO 2 emissions due to this upgrade comparing with the baseline house levels. Table 25 shows CO 2 emission levels for the same heating system with added solar DHW. The calculation assumes installation of 3.74 m 2 of evacuated tube panels with a 200L cylinder, able to provide 49% of annual water demand (excluding heat losses) for the 4 person family with a water usage of 32L/ day, as per section explanation. Insulation Level CO 2 Emissions from DHW Heating CO 2 Emissions from Space Heating CO 2 Emissions from Auxiliary Electricity CO 2 Emissions from PHE CO 2 Emission Savings Comparing to Baseline House A level % B level % C level % D level % Table 24. Breakdown of CO2 emissions for the new regular gas boiler heating system. Insulation Level CO 2 Emissions from DHW Heating CO 2 Emissions from Space Heating CO 2 Emissions from Auxiliary Electricity CO 2 Emissions from PHE CO 2 Emission Savings Comparing to Baseline House PHE A level % B level % C level % D level % Table 25. Breakdown of CO2 emissions for the regular gas boiler heating system and solar DHW. 41

55 Comparison of the last colums of tables 24 and 25 shows that the addition of the solar panels to the regular boiler installation increases the system s CO 2 savings by 3% to 4%. c. Annual CO 2 savings for upgraded system with a combination condensing gas boiler Table 26 shows CO 2 emission levels using 8kW, 91% efficient combination condensing gas boiler and the same heating control and distribution system insulation as for the regular boiler above. The combination boiler system eliminates hot water storage and some distribution losses. As the combi boilers are not usually recommended for installation with solar thermal panels, this option is not considered here. Insulation level CO 2 Emissions from DHW Heating CO 2 Emissions from Space Heating CO 2 Emissions from Auxiliary Electricity CO 2 Emissions from PHE CO 2 Emission Savings Comparing to Baseline House PHE A level % B level % C level % D level % Table 26. Breakdown of CO2 emissions for the components for the upgraded combi gas boiler heating system for four levels of building fabric upgrade. Despite the savings in hot water demand related CO 2 emissions, combi boiler system is saving only about 1% more emissions than the regular boiler, comparing to the baseline house. d. Annual CO 2 savings for upgraded system with a biomass boiler without and with solar thermal heating Table 27 shows CO 2 emission levels using 8kW, 95% efficient pellet stove with the same heating control and distribution system insulation as for the gas boilers above. The impact of the use of solar thermal heating with the biomass stove system is shown in Table 28. Solar panels used here have the same specification as those in section b. Insulation Level CO 2 Emissions from DHW Heating CO 2 Emissions from Space Heating CO 2 Emissions from Auxiliary Electricity CO 2 Emissions from PHE CO 2 Emission Savings Comparing to Baseline House PHE A level % B level % C level % D level % Table 27. Breakdown of CO 2 emissions for the wood pellet stove heating system. 42

56 Insulation Level CO 2 Emissions from DHW Heating CO 2 Emissions from Space Heating CO 2 Emissions from Auxiliary Electricity CO 2 Emissions from PHE CO 2 Emission Savings Comparing to Baseline House PHE A level % B level % C level % D level % Table 28. Breakdown of CO2 emissions for the wood pellet stove heating system and solar DHW. The CO 2 savings for wood pellets stove system upgrade are substantially higher than for all the other options. Two factors influence its lower CO 2 emissions: its better efficiency and more importantly the substantial difference in fuel CO 2 emissions factor for pellets (0.203 kgco 2 for gas comparing to kgco 2 for pellets for each kwh of energy delivered). The CO 2 emissions are so low, that comparing to the base house, the difference between the levels is very small. The increased impact of auxiliary electricity influences the performance of the solar water heating installed with the biomass boiler. The CO 2 emission due to solar system s additional auxiliary electricity exceeds the savings due to lower water heating demand. So, in this case, the addition of solar water heating actually increases the CO 2 emissions. The difference however is negligible, as can be seen when comparing the last columns in tables 27 and 28, while installation of the solar panels with conjunction with a biomass stove can have different merits, as explained in section 6.3. e. Annual CO 2 savings for upgraded system with a heat pump without and with solar thermal heating Table 29 shows CO 2 emission levels using 8kW air to water heat pump with an annual coefficient of performance (COP) of 3.0. The system uses the same heating controls and distribution system insulation as in section b. The impact of the use of solar thermal heating with a heat pump system is shown in Table 30. Solar panels used here have the same specification as those in section b. Insulation Level CO 2 Emissions from DHW Heating CO 2 Emissions from Space Heating CO 2 Emissions from Auxiliary Electricity CO 2 Emissions from PHE CO 2 Emission Savings Comparing to Baseline House PHE A Level % B Level % C Level % D Level % Table 29. Breakdown of CO2 emissions for the heat pump heating system. 43

57 Insulation Level CO 2 Emissions from DHW Heating CO 2 Emissions from Space Heating CO 2 Emissions from Auxiliary Electricity CO 2 Emissions from HE CO 2 Emission Savings Comparing to Baseline House PHE A Level % B Level % C Level % D Level % Table 30. Breakdown of CO2 emissions for the heat pump heating system and solar DHW. Electrically driven heat pump offers less CO 2 savings than a biomass boiler, but performs better than a gas boiler. It is worth noting that the COP of 3.0 used in this calculation represents an average performance. There are more efficient systems available on the market but they would be more expensive. Since the pump is to be replaced in 15 years possibly by a better performing one, it is not essential to invest in the best possible performing system available today. The performance of this heating system can be enhanced from 2% to 3% by adding the solar panels Summary Figure 15 summarizes the performance of all the investigated heating systems in terms of the CO 2 emissions reductions in the case study house. Figure 15. Comparison of annual CO2 emissions for different heating systems. 44

58 It can be noticed that the very low CO 2 emission factor for wood pellets in biomass boiler system makes the system outstanding in the environmental category. Its emissions are so low that there is very little difference across the four levels of the fabric upgrade. As mentioned before, solar panels have very little influence on environmental performance in this system. For all the other heating system upgrade solutions it can be noticed that Level A performs considerably worse than the other three options. Heat pump with solar thermal is the next best performing system, but its emissions are still considerably higher than for the biomass boiler option (4 times higher for level A and about 2 to 3 times higher for other levels). The performance of a regular gas boiler with solar DHW is very similar to that of the heat pump system without solar panels and is in the middle of the range of the researched systems. The smallest CO 2 emission savings are brought by the regular and combi gas boilers. 6.2 Economic validation Summary of capital costs for the four levels of the fabric upgrade Table 31 summarizes all the capital costs for the four levels of the fabric upgrade. Prices are taken from Chapter 5, from the column Capital Cost of each table. Measure A level B level C level D level Floor Insulation 1, , , ,915.1 Wall Insulation 11, , , ,786.9 Roof Insulation , , ,014.3 Windows 8, , , ,083.0 Air Tightness 2, , , ,615.0 Total Fabric Retrofit (FR) 25, , , ,414.3 Ventilation , , ,500.0 Total Fabric Retrofit +Ventilation (FR+V) 26, , , ,914.3 Regular gas boiler heating system 5, , , ,500.0 FR + V + Gas 31, , , ,414.3 Extra for added Solar Thermal system 3, , , ,600.0 FR + V + Gas + Solar DHW 35, , , ,014.3 Biomass boiler heating system 12, , , ,000.0 FR + V + Biomass 38, , , ,914.3 FR + V + Biomass + Solar DHW 41, , , ,514.3 Heat Pump 6, , , ,000.0 FR + V + Heat Pump 32, , , ,914.3 FR + V + Heat Pump+ Solar DHW 35, , , ,514.3 Table 31. Summary of Capital Costs for all the refurbishment measures for four levels of fabric upgrade. 45

59 6.2.2 Running cost of the heating system in existing house. Table 32 shows a summary of Annual Energy Costs for the existing heating system in the existing case study house. Heating Energy Use - Gas [kwh//y] Heating Energy Use - Electricity [kwh//y] Annual Cost of Energy Delivered [ /y] Existing house 49, ,236.1 Table 32. Annual Costs of Delivered Energy for existing heating system in existing house Economic analysis of the building fabric upgrade levels Table 33 shows a summary of an annual investment costs for the existing heating system in the case study house for four levels of building fabric and ventilation upgrade. Capital Cost of Improvements Additional costs over 30 years Governmental Inscentives Residual value of building fabric improvements after 30 years Final Cost of Improvements over 30 years Annual Loan Repayment Annual Maintenance Costs Total Annual Spend A Level 26, , , B Level 30, , , , , ,211.4 C Level 35, , , , , ,555.6 D Level 42, , , , , ,874.4 Table 33. Annual Investment Costs for four levels of upgrade with old boiler heating system Table 34 shows a summary of calculations of the annual costs of energy delivered. Heating Energy Use - Gas [kwh//y] Condensing gas boiler Heating Energy Use - Electricity [kwh//y] Annual Cost of Energy Delivered [ /y] A Level 15, ,043.8 B level 11, C level 10, D level 10, Table 34 Annual Costs of Delivered Energy for the old boiler heating system. 46

60 The savings brought by each level of the upgrade are summarized in Table 35. They are calculated by deducting annual investment costs and delivered energy costs of the upgraded options from the annual energy cost of the original house. Original House Energy Cost Annual Investment Spend Upgraded House Energy Cost [ /y] Annual Cost Saved [ /y] A Level 3, , ,226.6 B Level 3, , ,204.9 C Level 3, , D Level 3, , Table 35 Annual Savings due to four levels of building fabric and ventilation upgrade. Table 35 shows that for the building fabric and ventilation upgrade, Level A brings the best savings. Annual savings from Level D is 51% lower than that from Level A. This means that the capital costs related to higher upgrade are not recovered by the annual energy costs savings due to smaller energy demand Economic analysis of the heating systems a. New regular condensing gas boiler heating system without and with solar thermal heating Tables 36 and 37 show a summary of calculations of the total annual spend due to upgrade investments for each level of fabric upgrade, calculated as per methodology described in section (points 1-7). Table 36 presents heating system with a regular gas boiler and Table 37 adds the solar thermal heating with the installation described in section b. Capital Cost of Improvements Additional Costs over 30 years Governmental Inscentives Residual Value of Building Fabric Improvements after 30 Years Final Cost of Improvements over 30 years Annual Loan Repayment Annual Maintenance Costs Total Annual Spend A Level 31, , , , ,445.7 B Level 38, , , , , ,786.9 C Level 44, , , , , ,225.7 D Level 47, , , , , ,306.8 Table 36. Annual Investment Costs for regular gas boiler heating system. 47

61 Capital Cost of Improvements Additional costs over 30 years Governmental Inscentives Residual Value of Building Fabric Improvements after 30 Years Final Cost of Improvements over 30 years Annual Loan Repayment Annual Maintenance Costs Total Annual Spend A Level 35, , , , , ,702.4 B Level 41, , , , , ,043.6 C Level 48, , , , , ,482.4 D Level 51, , , , , ,563.5 Table 37. Annual Investment Costs for regular gas boiler heating system plus solar DHW. Table 38 shows a summary of calculations of the annual costs of energy delivered for each level of fabric upgrade for a new gas boiler heating system without and with the solar DHW installation, calculated as per methodology described in section (point 8). Regular Gas Regular Gas + Solar DHW Heating Energy Use - Gas [kwh//y] Heating Energy Use - Electricity [kwh//y] Annual Cost of Energy Delivered [ /y] Heating Energy Use - Gas [kwh//y] Heating Energy Use - Electricity [kwh//y] Annual Cost of Energy Delivered [ /y] A level 10, , B level 7, , C level 5, , D level 4, , Table 38. Annual Costs of Delivered Energy for new regular condensing gas boiler heating system and the same system with solar DHW installation. 48

62 b. Combination condensing gas boiler heating system The total annual spend due to upgrade investments is shown in Table 39. Capital Cost of Improvements Additional costs over 30 years Governmental Inscentives Residual Value of Building Fabric Improvements after 30 Years Final Cost of Improvements over 30 years Annual Loan Repayment Annual Maintenance Costs Total Annual Spend A Level 31, , , , ,469.4 B Level 38, , , , , ,810.7 C Level 44, , , , , ,249.5 D Level 47, , , , , ,330.5 Table 39. Annual Investment Costs for combination gas boiler heating system. Table 40 shows a summary of calculations of the annual costs of energy delivered for this option. Heating Energy Use - Gas [kwh//y] Heating Energy Use - Electricity [kwh//y] Annual Cost of Energy Delivered [ /y] A Level 10, B Level 6, C Level 4, D Level 4, Table 40. Annual Costs of Delivered Energy for four levels of fabric upgrade and new combination gas boiler heating system. Even though the combi boiler limits energy losses due to hot water storage and saves energy produced by gas boiler, the slight increase on more expensive electricity makes the saving in annual cost of delivered energy very small. Thus, in economic terms the impact of both of those boilers is very similar. c. Biomass boiler heating system: without and with solar thermal heating The pellet boiler considered in this example is more expensive than a gas boiler, there is also no grant for this source of heating currently in Ireland. However, good pellet boilers have a longer life expectancy of years, so it is assumed there will be no need for the boiler replacement during the 30 years of operation. Also, the servicing is only bi-annual as opposed to annual requirement for a gas boiler. Thus, the total annual spend over 30 years is only slightly higher for a pellet boiler than for gas boiler, as set out in Table

63 Capital Cost of Improvements Additional costs over 30 years Governmental Inscentives Residual Value of Building Fabric Improvements after 30 Years Final Cost of Improvements over 30 years Annual Loan Repayment Annual Maintenance Costs Total Annual Spend A Level 38, , , , ,760.0 B Level 44, , , , , ,082.1 C Level 51, , , , , ,496.0 D Level 53, , , , , ,577.0 Table 41. Annual Investment Costs for biomass boiler heating system. Table 42 shows a summary of calculations for a biomass boiler with solar DHW. The calculation assumes the same solar panels installation as in section Capital Cost of Improvements Additional costs over 30 years Governmental Inscentives Residual Value of Building Fabric Improvements after 30 Years Final Cost of Improvements over 30 years Annual Loan Repayment Annual Maintenance Costs Total Annual Spend A Level 41, , , ,778.9 B Level 48, , , , , ,110.6 C Level 54, , , , , ,549.4 D Level 57, , , , , ,630.4 Table 42. Annual Investment Costs for regular gas boiler heating system plus solar DHW. The annual energy costs are slightly lower than those of gas boiler due to better boiler efficiency and less expensive fuel (kwh delivered by pellets is 5 cents versus 6.2 cents of one kwh delivered by gas). Table 43 compares the costs of delivered energy for biomass boiler without and with solar DWH. Heating Energy Use - Pellets [kwh//y] Biomass boiler Heating Energy Use - Electricity [kwh//y] Annual Cost of Energy Delivered [ /y] Heating Energy Use - Pellets [kwh//y] Biomass boiler + solar DHW Heating Energy Use - Electricity [kwh//y] Annual Cost of Energy Delivered [ /y] A Level 10, , B Level 6, , C Level 5, , D Level 4, , Table 43. Annual Costs of Delivered Energy for biomass boiler heating system without and with the solar DHW. 50

64 d. Heat pump without and with solar thermal heating The cost of heat pump is only slightly higher than that of the gas boiler and it has similar life expectancy. However, there is no governmental grant for its installation so the final investment costs are higher comparing to the gas boiler. Tables 44 and 45 set out the annual investment costs for heat pump system without and with the solar DHW. Capital Cost of Improvements Additional Costs over 30 years Governmental Inscentives Residual Value of Building Fabric Improvements after 30 Years Final Cost of Improvements over 30 years Annual Loan Repayme nt Annual Maintenance Costs Total Annual Spend A Level 32, , , , ,579.3 B Level 38, , , , , ,911.1 C Level 45, , , , , ,349.9 D level 47, , , , , ,430.9 Table 44. Annual Investment Costs for heat pump heating system. Capital Cost of Improvements Additional costs over 30 years Governmental Inscentives Residual Value of Building Fabric Improvements after 30 Years Final Cost of Improvements over 30 years Annual Loan Repayment Annual Maintenance Costs Total Annual Spend A Level 35, , , , ,836.1 B Level 42, , , , , ,167.8 C Level 48, , , , , ,606.6 D Level 51, , , , , ,687.7 Table 45. Annual Investment Costs for heat pump heating system and solar DHW. In case of the heat pump, the much better efficiency of the system (300%) is counter-balanced by the fact that it uses much more expensive electricity for running. Table 46 compares annual spending on fuel for heat pump without and with solar DWH. Heating Energy Use - Electricity [kwh//y] Heat Pump Heating Energy Use - Electricity [kwh//y] Annual Cost of Energy Delivered [ /y] Heating Energy Use - Electricity [kwh//y] Heat Pump + solar DHW Heating Energy Use - Electricity [kwh//y] Annual Cost of Energy Delivered [ /y] A Level 3, , B Level 2, , C Level 1, , D Level 1, , Table 46. Annual Costs of Delivered Energy for heat pump system without and with solar DHW. 51

65 In this case the decreased demand for water heating due to solar panels installation makes a bigger difference as the energy saved would be produced by the expensive electricity Summary The annual investment repayment amounts for upgraded systems are presented in Table 47. The least expensive instalments are for the regular gas boiler installation and the most expensive those for the biomass system + solar DHW. Not surprisingly, systems with solar DHW are more expensive than those without solar panels. However, the biomass boiler without solar thermal heating is located in the middle of the scale it is less expensive than the regular boiler + solar DHW. Insulation Level Baseline Reg. Gas Combi Gas Heat Pump Biomass Reg. Gas + Solar DHW Heat Pump + Solar DHW Biomass + Solar DHW A Level 0.0 1, , , , , , B Level 0.0 1, , , , , , C Level 0.0 2, , , , , , D Level 0.0 2, , , , , , Table 47. Annual Investment Costs for each upgraded heating system. The annual running costs of each heating system considered are compared in Table 48, together with the original system costs. The least expensive solution is the biomass boiler and the most expensive the regular gas boiler. The systems with solar heating panels are generally less expensive to run than those without them. Insulation Level Baseline Reg. Gas Heat Pump Combi Gas Reg. Gas + Solar DHW Heat Pump + Solar DHW Biomass Biomass + Solar DHW A Level 3, B Level 3, C Level 3, D Level 3, Table 48. Annual Costs of Delivered Energy for each upgraded heating system. Tables 49 to 52 show annual savings due to implementation of levels A to D of refurbishment. The heating systems have been lined up from the biggest to the smallest savings. They are calculated by deducting the annual running and investment costs of each upgraded option from the costs of energy bills for the original house. 52

66 Biomass Reg. Gas Combi Gas Heat Pump Reg. Gas + Solar DHW Biomass + Solar DHW Heat Pump + Solar DHW , , Table 49. Annual savings due to the level A refurbishment for each heating system. Combi Gas Reg. Gas Biomass Heat Pump Reg. Gas + Solar DHW Biomass + Solar DHW Heat Pump + Solar DHW Table 50. Annual savings due to the level B refurbishment for each heating system. Combi Gas Reg. Gas Biomass Heat Pump Reg. Gas + Solar DHW Heat Pump + Solar DHW Biomass + Solar DHW Table 51. Annual savings due to the level C refurbishment for each heating system. Combi Gas Reg. Gas Biomass Heat Pump Reg. Gas + Solar DHW Heat Pump + Solar DHW Biomass + Solar DHW Table 52. Annual savings due to the level D refurbishment for each heating system. All the considered system upgrades make financial sense over 30 years, as every one of them pays back (the savings in energy bills exceed loan costs). It is interesting to note that the net gains are lower for levels with higher investment costs. This means that the rise in upgrade investment is not directly correlated with savings on energy costs. For level A, the biomass boiler has the best performance as the larger amount of heat is delivered by the cheap fuel the larger investment costs is balanced by larger savings on energy delivered. In options B to D, the largest profits from investment are brought by regular and combi gas boilers as the more expensive fuel only has to cover very small heating demand and the investment costs are smaller. The increased costs of systems including solar DHW are not fully recovered by savings in running costs, so those systems bring the smallest savings. 53

67 6.3 Social considerations As mentioned in section 4.2.3, social considerations are qualitative and difficult to evaluate but they could influence the decision making when other factors do not provide conclusive answer. The most important factor occupant s satisfaction is likely to increase following any of the proposed levels of fabric refurbishment and heating systems. However, the higher levels of fabric upgrade (using more insulation on external elements) will ensure higher temperatures of those surfaces and more comfortable distribution of heat. The tests made by the Passivhaus Institute (Feist, 2007) have shown that the difference of internal air and building s surface temperature should not be higher than 1 degree for the optimal comfort conditions. That could be achieved for levels C and D of floor, walls and roof insulation (U=0.15 W/m 2 /K or smaller) but only for level D for the windows (Passivhaus certified model). A study (Schnieders, 2004) considering the performance of the Passivhauses in Europe has shown that the occupant s satisfaction with internal temperatures and ventilation system with heat recovery is very high. User-friendliness of the service systems and the occupier s ability to operate them in the appropriate manner is extremely important to ensure their performance is both the most efficient and ensures satisfaction. Macintosh and Steemers s (2005) study of the MVHR performance in a new housing scheme in London concluded that the lack of occupant s knowledge of how to operate them led to substantial discrepancies between the modelled and actual performance, making the installation a failure. The biomass boiler may seem a difficult to deal with option for the heating system as the least expensive version of the wood pellet stove used in the case study house example is manual fed and needs to be cleaned at least once a week by the user. It also requires storage space for pellets. However, the awareness of contributing to reduction of the CO 2 emissions could be a sufficient factor to overcome the inconveniences. Another appealing factor may be its vernacular character: the stove located in living room looks and behaves like a fireplace, which can be considered pleasant. This is where the addition of the solar panels complements that approach the stove would not have to be used in the sunny summer days at all, as the solar thermal heating could cover water heating demand. Choosing products made locally is a good example of responsible sourcing due to the saved CO 2 emissions for transport. There are more and more insulation materials and mechanical systems manufactured in Ireland and they should be the first choice when sourcing building components. 54

68 7 Discussion This chapter discusses the finding from the analysis conducted in Chapter 6 - it concludes the effects of the four levels of building fabric and ventilation upgrades and different heating systems choices in the light of environmental, economic and social factors. Finally, recommendations for homeowners and advice for possible governmental incentives are proposed. 7.1 Environmental factor With regards to the level of building fabric upgrade, the application of the least expensive and simple refurbishment level A provides 79% of the CO 2 saving in space heating demand. Installation of Level B adds further 8%, Level C 11% and Level D cuts emissions by additional 13% and brings them up to 92% comparing to the baseline. The analysed emissions consist of space heating related gas emissions from the boiler and auxiliary electrical emissions. As can be seen on the graphs in Fig.14 from section , the biggest saving from a single measure is brought by the wall insulation. However, applying all the measures, even in the lowest proposed Level A gives better results than upgrading only one measure to the highest Level D. Of course, the deepest retrofit approach of applying all measures to Level D ensures the best result. When it comes to the choice of heating system, the analysis in section presents the differences in CO 2 emissions for different heating systems for space and water heating and auxiliary electricity. The biomass heating system is a definite winner from the environmental point of view with a 95% CO 2 emission savings comparing to the original baseline house. However, the extremely low emissions make the difference between lower and higher levels of building fabric upgrade negligible. Table 53 shows a summary of the percentage of CO 2 emission savings for all investigated systems comparing to the baseline emissions. Insulation Level Reg. Gas Combi Gas Reg. Gas + Solar DHW Heat Pump Heat Pump + Solar DHW Biomass + Solar DHW Biomass A Level 76% 76% 76% 78% 82% 96% 96% B Level 83% 83% 84% 86% 88% 96% 96% C Level 86% 86% 87% 89% 90% 96% 96% D Level 87% 87% 88% 90% 91% 96% 96% Table 53. Summary of CO2 emissions savings for all heating systems for all upgrade levels. Except for the biomass boiler system, where CO 2 emissions are similar across all upgrade levels, for all other heating system options the emissions are considerably lower for upgrade levels B to D, with a difference of 10%-14% between Levels A and D. Also, the biggest difference within the upgraded levels is between levels B and C (6-8%), whereas differences between higher levels are in the range of 1-3%. Regarding the question of the installation the solar thermal heating, when it comes to CO 2 emission savings, they are beneficial for gas boiler and heat pump systems. However, they improve the performance of a gas boiler by only about 1% and a heat pump by 1%-4% across the upgrade levels. Solar panels have very little influence on environmental performance of the biomass boiler. 55

69 7.2 Economic factor The financial criterion is represented by the predicted annual savings, calculated as a difference between the annual cost of original heating bills and a sum of annual investment costs and energy costs of upgraded house. It has to be noted, that all the investigated heating system upgrades make financial sense over 30 years, because the savings in energy bills exceed investment costs. The question is which of them brings more savings. Regarding the savings due to the four levels of building fabric and ventilation upgrade, Level A performs the best. Table 35 from section shows annual savings from Level D at 51% lower than those from Level A. As explained in section , this due to the fact that the capital costs related to higher upgrades are not recovered by the annual energy costs savings due to smaller energy use. The situation does not change with regards to the choice of a heating system. The best return is brought by the level A of the upgrades, meaning that also in this case the higher investment cost does not incur higher savings on energy costs. Tables 49 to 52 in Chapter 6 present the savings for each level. The best performing system for Level A is a biomass boiler, closely followed by regular and combi gas boilers. For the level with the highest heating energy demand, which is satisfied the cheap wood pellets, the higher than for gas boiler capital cost of the biomass boiler is recovered by small running costs. For higher levels of building fabric insulation the two gas boilers perform better and the biomass boiler comes in third place. Here, smaller amount of less expensive pellets does not overcome the more expensive capital investment. However, the differences of savings for the first three best performing heating systems are not substantial. Interestingly, savings for Level B better performing boilers (both gas boilers and the pellet boiler) are bigger than for worse performing boilers for Level A (heat pump, and all the boiler systems with solar DHW). Table 54 shows the percentage of savings for all investigated systems comparing to the baseline 0%. Biomass [kgco 2/ ] Reg. Gas [kgco 2/ ] Combi Gas kgco 2/ ] Heat Pump [kgco 2/ ] Reg. Gas + Solar DHW [kgco 2/ ] Biomass + Solar DHW [kgco 2/ ] Heat Pump + Solar DHW [kgco 2/E] A Level 31.46% 31.31% 31.09% 27.54% 25.85% 24.96% 22.04% Combi Gas kgco 2/ ] Reg. Gas [kgco 2/ ] Biomass [kgco 2/ ] Heat Pump [kgco 2/ ] Reg. Gas + Solar DHW [kgco 2/ ] Biomass + Solar DHW [kgco 2/ ] Heat Pump + Solar DHW [kgco 2/E] B Level 27.86% 27.83% 26.17% 24.22% 22.52% 19.37% 18.72% Combi Gas kgco 2/ ] Reg. Gas [kgco 2/ ] Biomass [kgco 2/ ] Heat Pump [kgco 2/ ] Reg. Gas + Solar DHW [kgco 2/ ] Heat Pump + Solar DHW [kgco 2/E] Biomass + Solar DHW [kgco 2/ ] C Level 17.29% 17.05% 15.31% 13.38% 11.65% 7.88% 7.74% Combi Gas kgco 2/ ] Reg. Gas [kgco 2/ ] Biomass [kgco 2/ ] Heat Pump [kgco 2/ ] Reg. Gas + Solar DHW [kgco 2/ ] Heat Pump + Solar DHW [kgco 2/E] Biomass + Solar DHW [kgco 2/ ] D Level 16.02% 15.42% 13.44% 11.72% 9.99% 6.23% 5.87% Table 54. Summary of monetary savings for all heating systems for all upgrade levels. 56

70 The systems including solar DHW bring the smallest savings, because their increased cost is not fully recovered by savings in delivered energy. A factor that combines the environmental and economic views is the cost effectiveness of carbon reduction. It is summarized in Tables 55 to 58 for all the upgrade levels. The heating system choices are lined up from least to most expensive per tco 2 saved for every level. Biomass [ /tco 2] Biomass + Solar DHW [ /tco 2] Heat Pump [ /tco 2] Heat Pump + Solar DHW [ /tco 2] Reg. Gas [ /tco 2] Combi Gas [ /tco 2] Reg. Gas + Solar DHW [ /tco 2] Table 55. Cost effectiveness of carbon reduction for level A refurbishment, for all heating system options. Biomass [ /tco 2] Biomass + Solar DHW [ /tco 2] Reg. Gas [ /tco 2] Heat Pump [ /tco 2] Heat Pump + Solar DHW [ /tco 2] Combi Gas [ /tco 2] Reg. Gas + Solar DHW [ /tco 2] Table 56. Cost effectiveness of carbon reduction for level B refurbishment, for all heating system options. Biomass [ /tco 2] Reg. Gas [ /tco 2] Biomass + Solar DHW [ /tco 2] Heat Pump + Solar DHW [ /tco 2] Heat Pump [ /tco 2] Combi Gas [ /tco 2] Reg. Gas + Solar DHW [ /tco 2] Table 57. Cost effectiveness of carbon reduction for level C refurbishment, for all heating system options. Reg. Gas [ /tco 2] Biomass [ /tco 2] Biomass + Solar DHW [ /tco 2] Combi Gas [ /tco 2] Heat Pump [ /tco 2] Heat Pump + Solar DHW [ /tco 2] Reg. Gas + Solar DHW [ /tco 2] Table 58. Cost effectiveness of carbon reduction for level D refurbishment, for all heating system options. For options A to C, the most cost effective carbon reduction is performed by the biomass boiler heating. Only in option D it is overtaken by the regular gas boiler, but the difference is very small. The biomass boiler with solar thermal heating is only slightly worse performing than the pellet stove alone. The least effective system is the regular gas boiler with solar DHW for all levels of refurbishment. It can be noted that these results are similar to those resulting from applying economic criterion Level A of the upgrades brings the least expensive savings of one tone of CO 2. The best performing heating system is again the biomass boiler. 57

71 7.3 Social factor It is assumed that the thermal comfort is the most important social factor and the secondary aspect would cover the occupant's contentment with their newly renovated house's environmental performance. Level D of refurbishment provides the best internal comfort (as explained in section 6.3.) and the best environmental performance is offered by the biomass and heat pump heating systems with solar thermal heating, as set out in Table 53 above. Thus the best three options here include biomass boiler, biomass boiler + solar DHW and heat pump with solar DHW, all for level D of the refurbishment. 7.4 Summary The best heating system option under environmental factor is a biomass boiler, regardless for which upgrade level. Second best CO 2 emission savings are brought by the heat pump systems. As for the rest of the heating system options, they perform best for Level D of the upgrades. Solar DHW improves the performance of all the systems except for the biomass boiler, where it does not have much influence. It can be said that from the financial point of view, most of those rules are reversed. The most beneficial in terms of monetary savings are heating systems with Level A of the upgrades and addition of solar panels decreases the savings. The only factor that stays the same for both aspects is the use of the biomass boiler heating system, although it brings most monetary savings for Level A and for CO 2 savings the level of upgrades is not important. On the other hand, social factor recommends a biomass boiler with Level D of the upgrades. To conclude, the biomass boiler is the best performing heating system for all the factors. The level of upgrades choice depends on the approach. The cheapest option is Level A and the most comfortable is Level D. Governmental incentive could help the occupants choosing Level D in order to compensate the difference in monetary savings and make the deepest refurbishment the best choice. 7.5 Governmental incentives The measures listed by the National Plan (Ireland. Department of Communications, Energy and Natural Resources, 2009) described earlier in section 2.2 propose to bring savings of 2,436 ktco 2 in the residential sector. The plan also explains that the suggested savings propose only 75% of the committed target. Thus, to achieve 100% of the target, the residential sector would have to save further 812 ktco 2. Table 59 presents a summary of CO 2 emissions savings during seven years, up to 2020 (assuming the works are completed in 2013) due to different options of the case study refurbishment. Insulation Level Reg. Gas Combi Gas Reg. Gas + Solar DHW Heat Pump Heat Pump + Solar DHW Biomass + Solar DHW Biomass A level B level C level D level Table 59. CO 2 emissions savings in

72 Assuming Level A of a deep retrofit with biomass boiler, 20.4 tco 2 could be saved per one house in the 7 years of operation between 2013 and Nearly 12,000 houses would have to be upgraded on top of the already listed in the plan actions (Ireland. Department of Communications, Energy and Natural Resources, 2009), to achieve the target. This number is much lower than the 46,000 houses already addressed by the Irish grant schemes between 2009 and As explained in section 2.2, the current governmental incentives in Ireland cover only the grant schemes, which are supporting on average 1.8 measures per house. Two most popular measures installed (SEAI, 2010) were external insulation and gas boiler with heating controls. They would bring about 21 tco 2 emission savings in seven years. Thus, in order to cover the missing 812ktCO 2 of the savings, 39,000 houses would need to be addressed, over three times more than in case of the deeply retrofitted houses. This simplified calculation shows that deep retrofit could be easier to conduct because of the lower number of houses and possibly smaller administrative costs. In order to reduce the emissions in the quickest possible way to fill the gap recognized in the latest national plan, the government s goal should be to enable the deepest refurbishment. According to the findings of this study, it would suggest encouraging the biomass heating systems in conjunction with comprehensive building thermal refurbishment. This means the government should change its approach and start supporting deep retrofit instead of the grant system and promote biomass boilers rather than gas and oil boilers. The new incentives could base on the UK s pay as you save model, where the loan is administrated by the energy provider and the capital cost it invests is recovered in heating bills. Another approach is the German model, with the loans directly subsidised by the government. Of course, deep retrofit requires a much bigger capital investment than one or two measures supported by the grants. But in case of the most underinvested houses (such as the case study one) that investment brings profits when comparing to the cost of energy bills for the original house performance, even for a commercial interest rate. Thus, first of all such dwellings should be addressed and governmental efforts could focus on encouraging the public to refurbish them. 59

73 8 Conclusions 8.1 Summary of the findings The aim of this study was to propose a methodology for evaluation of an energy efficient refurbishment for a typical 1960 s semi-detached Dublin house. The research offers information about best refurbishment choices from different angles, providing a comprehensive overview of the subject. First, the suitable measures for building fabric and new ventilation strategies are described and evaluated. Four levels of upgrades achieving different depths are proposed. Their suitability with regards to the building physics is explored and possible space heating energy savings are calculated. The suitable new heating systems and renewable technologies are also proposed and their impact on the primary energy use is assessed. The second stage analyses both the building fabric upgrade levels and different heating system options under economic, environmental and social factors. It quantifies the CO 2 emission and monetary savings associated with the different options of refurbishment using the life cycle analysis. The final conclusions propose solutions optimal taking into account all the factors. The first novelty of this thesis is an individual approach to the retrofit of a specific building type chosen for the case study. The problem is investigated in two steps. The first one is discussed in Chapter 5 and it evaluates measures for building fabric and ventilation upgrade. It proposes four levels of upgrades and explores their space heating energy savings possibilities. It also calculates the primary energy savings due to installation of the suggested new heating systems and renewable technologies showing differences between the systems. Second analyses the heating system options under economic, environmental and social factors. It is conducted in Chapter 6 and it quantifies the CO 2 emission and monetary savings associated with the different options of refurbishment using the life cycle analysis. The conclusions discussed in Chapter 7 provide support for decision making. The second innovative approach includes looking at the refurbishment task from two angles: the advice for homeowners and recommendations for the wider national aspect. The described methodology suggests certain solutions for this particular example but at the same time provides general guidelines as to how to choose the suitable measures and analyse their performance taking into account different priorities. The thesis discusses Ireland s environmental commitments and planned actions for the CO 2 emission savings. It points out deficiencies in the current programmes and proposes to focus on addressing the existing problematic housing stock in a more comprehensive manner. It is also suggests to introduce more suitable incentives using the example of German and British approach for financing deep retrofit. The important finding is that only a deep retrofit can bring serious CO 2 emission savings, which means that all elements of the building have to be upgraded. Discussions in Chapter 7 revealed that there is a discrepancy between financial and social aspects of the refurbishment. Higher levels of insulation bring less return on the investment, but they guarantee better thermal comfort. Lower loan interest rates for retrofits could encourage home owners to invest in higher levels of deep retrofit. However, their availability should depend on the depth of the retrofit. The basic threshold could be a 75% improvement in water and space heating related CO 2 emissions, possible to achieve with any of the options discussed in this study. Higher improvements could be encouraged by even less expensive loan interest rates. 60

74 8.2 Limitations A semi-detached house is an average type, between detached and terraced houses in terms of building geometry and size. It was selected as a house type for the case study also because it was the most popular at the time when it was built. However, focussing on one type and not extending the findings on the wider stock is a limitation of this thesis. This study focussed on the elements and systems directly connected with the building envelope. Throughout the analysis, the savings in CO 2 relate to energy connected with space and water heating and not the energy the house will use in total. The efficiency of electrical appliances and lighting was not investigated and their energy use was not included in the calculations. This approach has its merits but does not provide information about full energy savings potential and is limited in this regard. Another limitation is the lack of investigation of the renewable sources of electricity, especially the photovoltaic panels. The influence of the use of renewable electricity on the performance of heat pumps and biomass boilers could possibly change the final conclusions. However, the wide field of the solar electricity could become a topic of a separate discursion, so it did not fit in the scope of this study. All the calculations in Chapter 6 that form a base for discussions are assuming that replaced ventilation and heating systems will have the same performance and price in 15 years. This is most probably not going to be the case, as the technology is developing much faster in these areas and systems are becoming more efficient and less expensive. The calculations are also assuming the fossil fuel prices will remain unchanged over the next 30 years, which most definitely is not going to be valid. However, the intention was to show the performance of the refurbishment measures in the worst case scenario and it is most probable that all the investigated investments will bring even more profits. 8.3 Further research It was shown that the need for research in the general field of energy efficiency in the existing building is undeniable. Results of this study proved that in case of the investigated house, investing in energy efficient upgrades bring savings when the total spending cost is compared to energy bills cost in the inefficient house. As mentioned in section 8.2, in order to fully understand the potential of energy and CO 2 savings, buildings of other orientation, types and ages should be investigated as well. The presented methodology has been carefully explained in Chapter 4 allowing to be used by others for performing similar calculations for different house types and other conditions. Research in the available energy efficient household appliances and lighting as well as the impact of the behavioural changes with regards to electricity use would be valuable for the homeowners to understand the possible CO 2 emission savings in the whole household. In addition to this, investigation of the renewable electricity production installations, such as photovoltaic panels, would help determining the economic viability of investment in more efficient electrical appliances and renewable sources, similarly as it was conducted for heating energy. Biomass boilers and especially stoves that act like boilers still remain a reasonably unknown heating system type in Ireland. It was proven that it is a preferable technology from the point of view of its low CO 2 emissions and competitive cost of performance over 30 years. However, the inconveniences of its operation and high initial cost might still be discouraging for the general public. Thus more research and publications showing their advantages and support of demonstration installations would be beneficial. 61

75 9 References Austrian Institute for Healthy and Ecological Building (2009) Details for Passive Houses. A catalogue of ecologically rated constructions. 3rd ed., Austria: SpringerWienNewYork Azhar, S., Brown, J., Farooqi, R. (2009) BIM-based Sustainability Analysis: An Evaluation of Building Performance Analysis Software [Online] Available at: (Accessed: 19 April 2012). CODEMA DIT Partnership (2005) Energy Performance Survey of Irish Housing. Final Report. [Online] Available at: (Accessed: 23 March 2012). Colley, J. (2011) Unpublished SEAI Report: key findings revealed. Construct Ireland. 9 (5) Commission of the European Communities (2008) Second Strategic Energy Review. An EU Energy Security and Solidarity Action Plan [Online] Available at: (Accessed: 26 March 2012). EREC (2000) Technology Factsheet: Passive Solar Design. [Online] Available at: (Accessed 13/03/2012) EREC - Energy Efficiency and Renewable Energy Clearinghouse EST (2011) Sustainable refurbishment [Online] Available at: Sustainable-Refurbishment-2010-edition (Accessed: 8 May 2011) EST - Energy Saving Trust European Commission (2011) Energy Efficiency Plan [Online] Available at: (Accessed: 21 March 2012). European Parliament (2010) Directive 2010/31/EU of the European Parliament and of the Council on the energy performance of buildings (recast) [Online] Available at: EN:PDF (Accessed: 20 March 2012). Feist, W., Pfluger, R., Kaufmann, B., Schnieders, J. and Kah, O. (2007) Passive House Planning Package Requirements for Quality Aprroved Passive House (2007). [Computer program]. Passivehaus Institut. Darmstadt. Feist, W. (no date) Cost-Efficient Passive Houses in a Central European Climate. [Online] Available at: (Accessed: 29 March 2012). Feist, W. (no date) Cost-Efficient Passive Houses in a Central European Climate. [Online] Available at: (Accessed: 29 March 2012). Harris, C. and Borer, P. (2005) The whole house book. 2nd ed., Aberystwyth: Centre for Alternative Technology Hill, F., Lynch, H., Levermore, G. (2011) Consumer impacts on dividends from solar water heating.' Energy Efficiency. 4 (2011)

76 Ireland. Department of Communications, Energy and Natural Resources (2009). Maximising Ireland s Energy Efficiency. The National Energy Efficiency Action Plan [Online] Available at: NEEAP_full_launch_report.pdf (Accessed: 23 March 2012). Ireland. Department of Communications, Energy and Natural Resources (2012). Better Energy: the National Upgrade Programme [Online] Available at: Better+Energy.htm (Accessed: 4 July 2012). Ireland. Department of Environment, Heritage and Local Government (2008) Part L Supplementary Documents Acceptable Construction Details.Internal wall insulation. [Online] Available at: FileDownLoad,18753,en.pdf (Accessed: 4 July 2012). Ireland. Department of Environment, Heritage and Local Government (2011) Building Regulations 2011, Technical Guidance Document Part L: Conservation of Fuel and Energy Dwellings. Stationery Office, Dublin Jenkins, D.P., Peacock, A.D., Banfill, P.F.G., Kane D., Ingram V., Kilpatrick, R. (2012) Modelling carbon emissions of UK dwellings The Tarbase Domestic Model.' Applied Energy. 93 (2012) Konstantinou, T., Knaack, U. (2011) Refurbishment of residential buildings: a design approach to energy-efficiency upgrades.' Procedia Engineering. 21 (2011) Kwok, A. and Grondzik, W. (2011) The Green studio handbook, environmental strategies for schematic design. 2nd ed., USA: Elsevier Macintosh, A. and Steemers, K. (2005) Ventilation strategies for urban housing: lessons from a PoEcase study Building Research & Information 33 (2005) Natural Resources Canada (2012) RETScreen Software Suite (Version 4) [Computer program]. [Online] Available at: (Accessed: 20 July 2012). Schimschar, S., Blok, K., Boermans, T., Hermelink, A., (2011) Germany s path towards nearly zeroenergy buildings enabling the greenhouse gas mitigation potential in the building stock.' Energy Policy. 39 (2011) SEI (2007) Sustainable Energy Ireland's House of Tomorrow Programme supports 5000 homes. [Online] Available at: House_of_Tomorrow_Programme_supports_5000_homes.html (Accessed: 4 July 2012). SEI - Sustainable Energy Ireland SEI (2009) Retrofitted Passive Homes. Guidelines for upgrading existing dwellings in Ireland to the Passivhouse standard. [Online] Available at: Retrofit_Guidelines.pdf (Accessed: 30 March 2012). SEAI (2010) Annual Report [Online] Available at: (Accessed: 2 April 2012). SEAI - Sustainable Energy Authority of Ireland 63

77 SEAI (2012) Domestic Fuels Comparison of Energy Costs [Online] Available at: Domestic_Fuel_Costs_Comparison_April_2012_pdf.pdf (Accessed: 15 June 2012). SEAI (2012A) Domestic Fuels Comparison of Energy Costs [Online] Available at: Costs_Comparison_April_2012_pdf.pdf (Accessed: 15 June 2012). SEAI (2012B) What grants are available? [Online] Available at: Are_Available (Accessed: 19 July 2012). SEAI (2012C) Dwellings Energy Assessment Procedure (DEAP) [Online] Available at: (Accessed: 20 July 2012). Schnieders, J. and Hermelink, A. (2004) CEPHEUS results: measurements and occupant s satisfaction provide evidence for Passive Houses being an option for sustainable building Energy Policy 34 (2006) Tucker, S. (2003) Thermal Mass in Buildings. CEM 159, MSc Architecture: Advanced Environmental and Energy Studies by Distance Learning, Graduate School of the Environment, Centre of Alternative Technology, Machynlleth. UK. Department for Communities and Local Government (2006) Building A Greener Future: Towards Zero Carbon Development [Online] Available at: (Accessed: 03 April 2012). UK. Department for Communities and Local Government (2009) Sustainable New Homes The Road to Zero Carbon. Consultation on the Code for Sustainable Homes and the Energy Efficiency standard for Zero Carbon Homes [Online] Available at: (Accessed: 16 April 2012). UK. Department of Energy and Climate Change (2009) The Government s Standard Assessment Procedure for Energy Rating of Dwellings [Online] Available at: (Accessed: 18 April 2012). UK. Department of Energy and Climate Change (2011) UK Report on Articles 4 and 14 of the EU Enduse Efficiency and Energy Services Directive (ESD). Update on progress against the 2007 UK National Energy Efficiency Action Plan [Online] Available at: (Accessed: 03 April 2012). Woodhead, D. (2010) A Methodology to Evaluate Ventilation Options for Existing Dwellings undergoing Low Carbon Retrofit Graduate School of the Environment, Centre for Alternative, MSc Architecture: AEES Xing, Y., Hewitt, N., Griffiths, P. (2011) Zero carbon buildings refurbishment A hierarchical pathway.' Renewable and Sustainable Energy Reviews. 15 (2011)

78 Appendix A PHPP methodology The PHPP methodology is divided into the following tabs: - Areas where all the building external fabric areas (measured externally) are inputted; there is also a thermal bridge inputs table for determining the length and value of linear thermal bridges; Research presented by Feist (no date) shows that it is possible to avoid typical thermal bridges in super-insulated building envelopes if the connections between all elements are carefully designed. Regarding the unavoidable geometric thermal bridges, the PHPP methodology includes calculation of heat losses using external dimensions of the shell. This way the geometrical thermal bridges are accounted for in heat loss calculations and do not have to be considered separately. This approach was verified for the Passivhouse prototype buildings, where all joints have been calculated by two-dimensional heat flow programs; - U-list and U-values tabs where U-values of all fabric opaque elements are calculated according to ISO 6946 (for walls and roofs) and to ISO (for floors); input values include material types in the fabric element, their thermal conductivity and thicknesses; calculation is also provided for structures with bridged layers; - Ground where heat losses of the floors on the ground are calculated; it takes into account ground characteristics and floor slab type (advice on standard values is given and climatic data is automatically loaded from Climate tab); - Windows tab for specifying the window areas for each type and its orientation and tilt: U-value of frame and glazing, g-value, frame dimensions, and thermal bridges for spacer (manufacturer s value) and installation (depending on the way the window is installed); there is space for user inputs and some pre-defined choices; The use of triple glazed windows with insulated frames and spacers is very important for ensuring there are more gains from solar irradiation than heat losses and for maintaining comfortable temperature of the internal surface of the glazing (in the absence of any heating source close to windows). Windows located on the south elevation (in Northern hemisphere) have more gains then losses throughout the year, so it is very important in Passivhouse to maximize their area and minimizing them on other sides of the building as the solar gains are becoming an important source of heat. - Shading where shading devices corresponding to each window are specified; - Ventilation with inputs for: supply air per person (the number of occupants is based on the house s area, but can be also edited, number of extract fans (wet rooms), design air flow rate and air change rate; this tab also includes inputs for air infiltration - air change rate at pressurization test (the maximum allowed value for achieving the standard is 0.6 ac/h) and efficiencies for ventilation system; a mechanical ventilation system is necessary to guarantee good indoor air quality in an air-tight building. - Annual Heat Demand and Heating Load inputs are transferred from other tabs and the heat demand is calculated by adding transmission heat losses to ventilation heat losses and deducting solar and internal heat gains; it is assumed that the house is heated all year round to 20 degc, but the internal temperature can be altered if required; - DHW and Heating Distribution where the useful heat for hot water is calculated: the suggested usage is 25 L of hot water per person and the temperature of cold water is 10 degc; distribution heat losses for hot water and space heating are also taken into account, inputs include: lengths for distribution pipes, their insulation and a specific heat loss for storage cylinder; the factor of heat losses from distribution and storage that are utilized for space heating is calculated using data from climate tab; - Solar DHW where solar fraction for hot water heating is calculated using manufacturer s data for panels, and orientation and tilt of the panel; - Electricity and Auxiliary Electricity electricity use for dishwashing, washer and dryer, refrigerating, cooker, lighting, electronics and small appliances is estimated; guidelines are 65

79 provided, but can be overridden; Auxiliary Electricity tab copies data from other tabs with regards to electricity used for boilers, pumps, ventilation systems etc.; It is advised that appliances installed in Passivehouse are very efficient as well not only to limit the energy use, but also to minimize the internal heating gains in summer. It is recommended to connect washers and dishwashers to hot water system, use low energy lights and efficient fridges and freezers (max. 100 kwh/y and 117 kwh/y respectively); - Primary Energy Value converts the energy used to primary energy demand and CO 2 emissions; it is possible to use combination of heating systems; the non-renewable primary energy factor of the energy source is taken automatically from Data worksheet but can be altered; - Heating systems for back-up space heating and for top-up water heating can be chosen from: Compact heat pump unit, or District heating; each has an option for solar fraction for space heat; - Compact unit functions both as heat and hot water producer and a ventilation unit; the worksheet calculates the efficiency and primary energy demand of electrically driven Passivhouse certified units (using laboratory test data); the priority for hot water or space heating can be chosen; - the worksheet determines the boiler s performance ratio for the space and hot water heating; inputs include the heat source and heat generator data (from manufacturer or standard values from drop-down list); for DHW heating a year round operation of 8,760 hours is used, the length of space heating period is determined from the ratio of the space heat demand relative to the average annual heating demand; - District Heating includes systems such as hard coal burning district heating, natural gas cogeneration plant and oil cogeneration plant; it is also possible to include the fraction of cogeneration; - Climate Data worksheet includes data sets for annual heating demand (monthly average values for the outside temperatures, solar irradiation on the horizontal as well in the four main sky directions, the latitude, monthly dew point and sky temperatures) and for heating load for a number of European locations (including Dublin and Birr for Ireland); user-defined data can also be used or data can be imported from a program Meteonorm but climate data for the heating load can only be modelled by a dynamic simulation, not supported by PHPP (calculations are available for example from Passivhouse Institute) - Internal Heat Gains sheet is collecting data from Electricity and Auxiliary electricity tabs for internal gains from appliances and there is a standard of 80 W per person in the dwelling; the usability of heat source was established by Passivhouse Institute and tested in houses in Germany, but can be adjusted by the user; 66

80 Appendix B Tarbase methodology The Tarbase methodology is divided into following energy categories : - Appliances the model includes a database and allows for user-defined inputs, they are defined by average power consumption (W) and annual usage (h); to estimate the internal heat gain generated, they are divided into categories, defining the degree to which the appliance provides useful heat; - Lighting energy use for lighting is calculated for each zone, where different types of lighting can be associated with each room and the lighting model takes into account the required luminance and the lit area; heat gains are calculated for the heating period; - Water heating hot water use calculation depends on the daily volume of water required (V=46+(26xn) for n<5 and V=40+(28xn) for n>5 based on data collected in 120 dwellings) and establishes the energy required to raise the temperature of water taking into account immersion, pipes and heating system heat losses; - Space heating Jenkins at al. (2012) emphasize that all steady-state models have limitations with regards to space heating demands but Tarbase offers advantages of using specific internal activities and climate information and thus provides reliable guidance on how different measures might perform for specific scenarios; the heat loss of the dwelling fabric is calculated by multiplying U-values by respective elements areas and taking into account thermal bridges (assumed linear thermal bridges from SAP model); ventilation losses are based on air-tightness testing or estimated for dwellings on the base of age and user-defined data on window openings/vents and mechanical ventilation; the dwelling s heat losses are calculated taking into account the comfort internal temperature as an area-weighted room-specific figures (bedroom and kitchen 18 deg., bathroom 26.5 deg. and the rest of the house 21.5 deg., but can be altered by user); external temperatures can be chosen for specified locations or entered manually; the space heating consumption is calculated by deducting internal gains and solar gains from the heat losses and multiplying the result by degree hours (operation time of the boiler) and divided by the efficiency of the boiler; heat gains from people assume 84 W for male, 71W for female and 63 W for a child; boiler is assumed to operate 3553 h/year; electrical consumption of the boiler and associates uses is added to appliance section; As the Tarbase model was developed as refurbishment tool it allows for estimating the effect of a range of different technology options that can be applied in any order and is calculating the cumulative effect. Tarbase allows the user to choose refurbishment options from a list of demand side interventions: - Appliance and lighting a choice of domestic lighting and appliance improvements; - Fabric improvements the individual U-values would be changed, suggestions are provided for appropriate targets; glazing upgrade options can be chosen (with specified U-values and transmission factors); - Infiltration and ventilation rates the rates can be adjusted (with a range of recommended thresholds, also advising on the need for additional ventilation for maintaining air quality; for mechanical ventilation options (including heat recovery) it can be chosen if it works 24h or according to occupancy and a list of manufacturers with data on efficiency, electricity use etc. is provided; - Heating systems alternative heating upgrade options; calculation take into account new sources of heat production from renewable sources; - Externalities the model allows a change to grid carbon intensity, climate and internal comfort; the model allows specifying current and future grid carbon intensity, allowing this change to be used as a carbon-saving intervention with the effect shown separately. 67

81 The supply-side interventions include: - Solar thermal for water heating with area and tilt of panels to be inputted and assumed efficiency at 40% and for included climatic data; model provides recommendation what area will meet the 50% domestic hot water requirement to prevent oversizing; - Solar photovoltaic manufacturer s data on efficiency is used to calculate possible yields taking into account area and tilt of the panel; - Micro combined heat and power the model includes estimates of the potential savings possible when replacing conventional boilers with appropriately sized mchp units; - Heat pumps the model estimates the heat pump Coefficient of Performance (COP), based on assumes part-load performance, size of system and chosen climate (it can be also user-defined); there is also an option for satisfying the hot water demand by heat pumps; - Micro-wind rooftop turbines are usually not recommended for domestic sector but included in the model for reference default values are provided for generic calculations. 68

82 Appendix C Comparison between DEAP, PHPP and Tarbase methodologies Issue PHPP DEAP Tarbase Availability Climatic data and general approach Available to public (at cost of 50). Any European location (for Ireland two default locations, but possible manual climatic data input). Available to public (free). Specific for Ireland (one climatic data for any location) Not yet available to public. Specific for UK, includes some SAP calculations, which are very similar to DEAP, but includes local climate data and internal activity and occupancy variations. Best choice for energy calculation PHPP or DEAP. PHPP - includes the biggest choice of climatic data, flexibility and generally most detailed. External fabric elements areas Measured externally (to take account of geometrical thermal bridges). Measured internally. Measured internally. All options are OK (geometrical thermal bridges are accounted elsewhere in DEAP and SAP) U-values Internal spreadsheet for calculations in the ISO 6946 (for walls and roofs) and ISO (for floors) included. Need to be calculated outside of the software, to be based on ISO 6946 (for walls and roofs) and ISO (for floors). Need to be calculated outside of the software, to be based on ISO 6946 (for walls and roofs) and ISO (for floors). PHPP is the most convenient with the internal spreadsheets. Thermal bridges Input needed (thermal bridges to be calculated outside); general aprroach is to avoid them whenever possible using suitable details. Assumed linear thermal bridges (0.15 for all existing buildings, 0.11 for details built to 2005 regulations, 0.08 for details built to 2008 and 2011 regulations), or they can be calculated manually. Assumed linear thermal bridges from SAP model Thermal bridges have to be calculated outside for all the options, but the PHPP's aproach of avoiding thermal bridges whenever possible is convenient. 69

83 Windows Heat lossess and gains calculated using exact glazing and frame U-values, g-values, frame dimensions and individaual thermal bridges for each window; shading can be included for each window; exact orientation for each window Heat lossess and gains calculated using overall U- values and g-values; generic vlues for overshadowing. Heat lossess and gains calculated using overall U- values and g-values; generic vlues for overshadowing PHPP approach is the most detailed. Ventilation Air flow rate is specified (taking into account supply air per person and extract air requirement), air infiltration is taken from the air change rate at pressurization test (the maximum allowed value for achieving the standard is 0.6 ac/h) and manufacturer's efficiencies are applied for ventilation system heat recovery. Generic values are generated for the number of screened sides of the building, the air infiltration etc.; manufacturer's efficiencies are applied for ventilation system heat recovery. Air flow rate can be specified, manufacturer's efficiencies are applied for ventilation system heat recovery. PHPP approach is the most detailed. Number of occupants Manual input. Based on area. Manual input. PHPP and Tarbase have the same flexibility. Hot water usage [L/day] Manual input (suggested 25L/day/person). Number of occupants is ased on the area, water usage is based on the occupant number (40L/day/person). Sugested use V=46+(26xn) for n<5 and V=40+(28xn) for n>5 - based on analysis of usage patterns. PHPP and tarbase are flexible, but the usage needs to be calculated; Tarbase provides guidance for the calculations. Approach to retrofit No guidance, but allows for flexibility in adjusting it for the purpose of retrofit. No guidance and no flexibility. Includes a choice of improvement for domestic lighting and appliance, fabric insulation and windows, infiltration and ventilation, heating systems and renewable options. Only Tarbase provides guidance. 70

84 Appendix D Existing house specification and baseline settings for PHPP Below are dimensions and specifications for the existing case study house that are necessary to perform calculations in PHPP and the resulting heat losses. All external building elements areas are measured on the outside to account for the geometrical thermal bridges, as explained in Appendix A. Dimensions: Total Treated Floor Area [m 2 ] Ground floor height [m] 2.55 First floor height [m] 2.75 Floor Area [m 2 ] 53.6 Walls Area [m 2 ] Attic Ceiling Area [m 2 ] 44.2 Rafters at Wall Plate [m 2 ] 9.5 Windows and Door: Single glazed, metal frame without thermal break Total area [m 2 ] 17.8 Percentage of floor area 20.0% U-value [W/m 2 K] 5.5 Front windows area (SE) [m 2 ] 7.2 Percentage of SE wall area 20.0% Side windows area (NE) [m 2 ] 1.8 Percentage of NE wall area 4.0% Rear windows area (NW) [m 2 ] 8.8 Percentage of NW wall area 24.7% Front door area [m 2 ] 1.9 Side door area [m 2 ] 1.9 Door U-value [W/m 2 K] 3 Ground floor: Suspended timber floor Area [m 2 ] 53.5 Perimeter [m] 21.2 U-value [W/m 2 K] 0.68 Walls external: Hollow concrete block single leaf Area [m 2 ] U-value [W/m 2 K] 2.4 Party wall: Solid concrete Area [m 2 ] 47.1 U-value [W/m 2 K]

85 Roof at ceiling: Solid concrete Area [m 2 ] 53.5 U-value [W/m 2 K] 2.3 Airtightness and ventialtion: Assumed test results: 10 m3/h/ m2 = in this case: 10.6 ac/h Ventiltion: Natural, 2 x chimneys Thermal mass Thermally massive elements 5 Spec. Capacity 180 Summer shading reduction factors Blinds z 70.0% Activation factor 70.0% Zeffective 79.0% Domestic Water Heating Occupancy (2 adults + 2 children) [persons] 4 DHW consuption per person per day (at 60 o C) [L] 32 Lenght of distribution pipes for hot water (uninsulated): Circulation [m] 8.60 Individual [m] 6.50 Heat Loss Coefficient per m of pipe [W/m 2 K] 1.0 Design Flow Temperature [ 0 C] 60 Hot water cylinder (uninsulated) [L] Heat released from storage [K] Space Heating Gas Efficiency 78.0% Internal temperature [ 0 C] Heating pattern [hours/days] 24/7 Lenght of distribution pipes for space heating [m] 20 Heat Loss Coefficient per m of pipe [W/m 2 K] 1.0 Design Flow Temperature [ 0 C] 55 Heat Lossess: Floors [kwh/y] 2233 Walls [kwh/y] Roof [kwh/y] 7459 Windows [kwh/y] 5911 Doors [kwh/y] 688 Ventilation Heat Lossess [kwh/y] 5220 Solar Gains: 1502 Internl Gains: 897 Annual Heat Demand [kwh/y] Specific Annual Heat Demand [kwh/m 2 /y]

86 Appendix E Summary of capital costs for all refurbishment measures The table below shows the areas of building elements to which the costs of upgrade elements are applied. House Area [m 2 ] 87 Floor Area [m 2 ] 53.6 Walls Area [m 2 ] Internal Area of Walls (Plastering) [m 2 ] 95 Rising Walls Area [m 2 ] Attic Ceiling Area [m 2 ] 44.2 Rafters at Wall Plate [m 2 ] 9.5 Modified Roof Section [m 2 ] 16.0 Windows and Doors Area [m 2 ] 28.1 No. of Openings [pc] 11.0 The following tables present the costs elements of each upgrade measure and calculations of the total cost of each upgrade measure. Element cost row includes installation prices of each element per the unit. They are estimated by the author from the fee quotations from contractors for similar works on different projects from the past year and from supplier price lists published online. The following rows show calculations for each level of the upgrade. Total price per element is calculated as the price per square meter multiplied by the area of the element. Total cost of the level upgrade is a sum of the costs of all the elements that are applied in that option. Floor Insulation Total cost Sprayed foam ins. 110mm [ /m 2 ] White EPS 170mm [ /m 2 ] Phenolic ins. 170mm [ /m 2 ] Grey EPS 300mm [ /m 2 ] Concrete Slab + Screed + DPM [ /m 2 ] Chipboard flooring [ /m 2 ] Element Cost Level A 1, , Level B 3, , ,913.5 Level C 4, , ,913.5 Level D 4, , ,913.5 Total cost Woodfibre ins. Internally 80mm [ /m 2 ] Wall Insulation Grey EPS externally 150mm [ /m 2 ] Grey EPS externally 200mm [ /m 2 ] Grey EPS externally 300mm [ /m 2 ] Service Cavity + Intello Membrane + Plasterboard [ /m 2 ] Element Cost Level A 11, , ,125.4 Level B 12, ,414.9 Level C 13, ,641.1 Level D 15, ,

87 Roof Insulation Total cost Sprayed foam ins. 100mm [ /m 2 ] Sprayed foam ins. 50mm at Wall Plate [ /m 2 ] Sprayed foam ins. Additional 200mm [ /m 2 ] Sprayed foam ins. Additional 300mm [ /m 2 ] Timber Joists for Raised Floor [ /m 2 ] Modification of Roof Section [ /m 2 ] Element Cost Level A Level B 2, Level C 2, Level D 3, , Total cost Timber, Double Glazing (Ug=1.1, Uf=1.0, g=0.64, Ψ spacer =0.04 doors U=1.4 [ /m 2 ] Windows Timber, Triple Glazing (Ug=0.6, Uf=1.0, g=0.54, Ψ spacer =0.04 doors U=1.2 [ /m 2 ] Alu-clad, Triple Glazing (Ug=0.6, Uf=1.0, g=0.54, Ψ spacer =0.04 doors U=1.2 [ /m 2 ] Alu-clad, Triple Glazing, PassiveHouse certified (Ug=0.53, Uf=0.75, g=0.55, Yspacer=0.04 doors U=0.8 [ /m 2 ] Element Cost Level A 8, ,935.8 Level B 2, ,835.0 Level C 2, ,240.0 Level D 12, ,083.0 Air Tightness Total cost Chimney removal [ /pc] Taping Around Windows [ /pc] Existing 1 Floor Joists Remediation Wet Internal Plaster [ /m 2 ] Element Cost 1, Depending on Upgrade Level 14.0 Level A 2, , Level B 3, , ,330.0 Level C 3, , ,330.0 Level D 3, , ,

88 Ventialtion Total cost Type of ventialtion Level A Passive Stack Ventialtion Installation Level B 2,107.5 Demand Control Mechanical Ventilation Level C 3,500.0 Mechanical Ventilation with Heat Recovery Level D 3,500.0 Mechanical Ventilation with Heat Recovery Regular Condensing Gas Heating System Total cost Radiators GF Underfloor Heating + FF Radiators Heating Controlls New Insulated Piping New Insulated Hot Water Cylinder 100L Regular Gas Element Cost 1, , , , ,000.0 Level A 5, , , , ,000.0 Level B 6, , , , ,000.0 Level C 6, , , , ,000.0 Level D 4, , , ,000.0 Combination Condensing Gas Heating System Total cost Radiators GF Underfloor Heating + FF Radiators Heating Controlls New Insulated Piping Combi Gas Element Cost 1, , , , ,500.0 Level A 5, , , , ,500.0 Level B 6, , , , ,500.0 Level C 6, , , , ,500.0 Level D 4, , , ,500.0 Total cost Radiators Biomass Heating System GF Underfloor Heating + FF Radiators Heating Controlls New Insulated Piping New Insulated Hot Water Cylinder 100L Biomass Element Cost 1, , , , ,500.0 Level A 12, , , , ,500.0 Level B 12, , , , ,500.0 Level C 12, , , , ,500.0 Level D 11, , , ,

89 Total cost Evacuated Tube Panels 3.74m 2 Solar Panels Evacuated Tube Panels 4.68 m 2 Evacuated Tube Panels 5.61 m 2 Controls, Pumps, Heat Dump, Etc. Element Cost 2, , , m 2 evacuated tube panels + 200L cylinder 4.68 m 2 evacuated tube panels + 250L cylinder 5.61m 2 evacuated tube panels + 300L cylinder Overhead for Larger Hot Water Cylinder 4, , , , , , , , ,300.0 Heat Pump Heating System Total cost Radiators GF Underfloor Heating + FF Radiators Heating Controlls New Insulated Piping New Insulated Hot Water Cylinder 100L Heat Pump Element Cost 1, , , , ,500.0 Level A 6, , , , ,500.0 Level B 6, , , , ,500.0 Level C 6, , , , ,500.0 Level D 5, , , ,

90 Appendix F Phenolic insulation between timber joists When a closed cell, non breathable insulation material like phenolic board is installed between timber joists, it will not allow the water vapour through, so if any moisture gets through the barrier (for example if incorrectly fitted) it will get to the timber, which could cause its damage over time. The smaller the thermal conductivity of the insulation material, the bigger of a thermal bridge the timber joists are becoming and the bigger is the risk of water condensation in structural wood. Thus, phenolic insulation should only be installed between structural timber if there is limited space not allowing for installation of other breathable insulation material and under a condition that the water vapour (and air tightness) barrier can be installed as a continuous layer and will not be damaged during the lifetime of the installation. 77

91 Appendix G The influence of thermal mass Thermal mass can be defined as the quality of the building material that absorbs heat from a source (such as the sun), and then releases it back into the building. Thermally massive buildings have large areas of the internal wall and floor surfaces constructed from dense materials, such as stone or concrete (Tucker, 2003). In the passive solar building the heat from solar gains heat is stored in the thermally massive building elements. Heat storage saves the surplus energy for later (when the sun is gone) and also helps avoiding overheating. Its effectiveness is governed by: the heat storage capacity of the material, its volume and how the heat gets in and out. The amount of energy that building material can store (admittance) depends on its density, insulating value and thermal capacity. For most building materials, the range of useful thickness is from 50mm for lightweight materials, like plasterboard and timber to 150mm for denser materials, such as stone and concrete (Harris and Borer, 2005) The area of thermal mass required to store the solar heat can be estimated by a general rule. The heavy mass elements of a thickness of about mm that receive direct irradiation should be about three times the area of the solar glazing (Kwok and Grondzik, 2011). It needs to be twice as much for elements with reflected radiation. In the case study house the south-east solar collecting widows are 15.6m 2, so there would be a need of 47m 2 of directly irradiated heavy thermal mass. About 30m 2 is available on the ground floor for direct radiation (concrete floor). It would leave 17m 2 x 2 that could be covered by reflected radiation. There is 30m 2 of the dense concrete external or party walls on ground floor and additional 20m 2 on first floor which would cover the requirement (the thermal massive elements are marked on Figure 13 ). To help with heat absorption, the ground floor should be a dense concrete with a dark-coloured clay tiled surface. 78

92 Appendix H U-value calculations Wall - Level A Materials Thicknesses Conductivity Resistance [m] [W/mK] [m 2 K/W] External surface External render Concrete block Insulation 0.085* Internal plaster Internal surface Total thermal resistance 2.54 U-value [W/m 2 K] 0.39 *85mm is an area weighted thickness of insulation for internal application, taking into account no insulation at internal wall junctions and reduced thickness at wall floor joints connection. Wall - Level B Materials Thicknesses Conductivity Resistance [m] [W/mK] [m 2 K/W] External surface External render Concrete block Insulation Internal plaster Internal surface Total thermal resistance [m 2 K/W] 5.25 U-value [W/m 2 K] 0.19 Wall - Level C Materials Thicknesses Conductivity Resistance [m] [W/mK] [m 2 K/W] External surface External render Concrete block Insulation Internal plaster Internal surface Total thermal resistance [m 2 K/W] 6.87 U-value [W/m 2 K]

93 Wall - Level D Materials Thicknesses Conductivity Resistance [m] [W/mK] [m 2 K/W] External surface External render Concrete block Insulation Internal plaster Internal surface Total thermal resistance [m 2 K/W] U-value [W/m 2 K] 0.10 In case of the roof U-value, it is calculated as the area weighted value taking into account the main roof space and the wall plate area with reduced amount of insulation. Roof - Level A - main roof Materials Thicknesses Conductivity 1 Conductivity 2 [m] [W/mK] [W/mK] External surface Joists/ Insulation between joists Percentage of bridging layer 10% Plasterboard Internal surface Total thermal resistance [m 2 K/W] 2.38 U-value [W/m 2 K] 0.42 Roof - Levels B and C - main roof Materials Thicknesses Conductivity 1 Conductivity 2 [m] [W/mK] [W/mK] External surface Joists/ Insulation between joists Percentage of bridging layer 10% Plasterboard Internal surface Total thermal resistance [m 2 K/W] 7.14 U-value [W/m 2 K]

94 Roof - Level D - main roof Materials Thicknesses Conductivity 1 Conductivity 2 [m] [W/mK] [W/mK] External surface Joists/ Insulation between joists Percentage of bridging layer 10% Plasterboard Internal surface Total thermal resistance 9.09 U-value [W/m 2 K] 0.11 Roof - wall plate area 1 Materials Thicknesses Conductivity 1 Conductivity 2 [m] [W/mK] [W/mK] External surface Joists/ Insulation between joists Percentage of bridging layer 10% Plasterboard Internal surface Total thermal resistance 1.33 U-value [W/m 2 K] 0.75 Roof - wall plate area 2 Materials thicknesses conductivity 1 conductivity 2 [m] [W/mK] [W/mK] External surface Joists/ Insulation between joists Percentage of bridging layer 10% Plasterboard Internal surface Total thermal resistance 3.45 U-value [W/m 2 K] 0.29 Roof - Level A U-value [W/m 2 /K] Area [m 2 ] Ceiling Rafters at wall plate Area - weighted average

95 Roof - Level B U-value [W/m 2 /K] Area [m 2 ] Ceiling Rafters at wall plate Area - weighted average Roof - Level C U-value [W/m 2 /K] Area [m 2 ] Ceiling Rafters at wall plate Area - weighted average Roof - Level D U-value [W/m 2 /K] Area [m 2 ] Ceiling Rafters at wall plate Area - weighted average

96 Appendix I Internal or external wall insulation? First disadvantage of internal insulation includes reducing the internal area of the house (in case of existing houses it means decreasing the area that the homeowner has already paid for). Another drawback is connected with unavoidable thermal bridges (for example at junctions of internal walls or floors with the external wall), that not only weaken the thermal performance of the whole house, but also could cause condensation on the worse insulated building elements leading to structural damage. There is a common problem recognized with the interstitial condensation in internally insulated walls, which can lead to mould growth and deterioration of the insulation. It is usually caused by the incorrect installation of a vapour barrier, when the sheets are not continuous or it is punctured by building services (pipes, electrical sockets). It can also be damaged for example by nails installed during the building occupancy (for hanging things on the walls). It can be addressed by a careful design and installation of a vapour barrier. The joints between the vapour control sheets and connections with floors, ceilings and window reveals can be taped and sealed, while the problem with its penetration by services can be addressed by introducing an internal service zone in a form of a void created in front of the vapour barrier (Harris and Borer, 2005), as shown in Fig.7. However, introducing a service zone would impact the most important advantage of internal insulation, which is the low cost of its typical installation comparing with external insulation. In the past, issues connected with addressing thermal bridging and problems with keeping a continuous layer of vapour barrier have not been addressed, thus the cost of internal insulation have been significantly lower. Internal insulation is also lowering the thermal mass of the concrete walls, which can be seen either as a positive (because the house could possibly be heated quicker) or on the contrary as a drawback (because it will not keep the heat as well as exposed walls insulated externally), depending on the pattern the house will be used and the heating method. The main benefit of external insulation is a possibility of elimination of most of the thermal bridging (there could be problematic areas in connections of walls with roofs due to the geometry of the existing building), because the insulation layer is continuous (Fig.8.). More importantly, the problem with water vapour condensing does not exist, as the walls are kept on the warm side. One main disadvantage of external insulation is its cost. However, it can be mitigated if there is a need for a remedial work on external elevation anyway (for example to prevent rainwater penetration, or if the windows are being replaced or relocated). Its application both improves the dwelling s appearance and extends its lifespan. To conclude, it is proposed to use internal insulation in Level A, with 80mm of breathable woodfibre material and a 20mm cavity zone. A thicker insulation would take up too much space and the cavity zone ensures correct installation of vapour membrane. For all other levels it is proposed to install external insulation with varying depths. There is no limitation for external insulation depth as the soffits are wide enough to accommodate even 300mm. Thus the less expensive EPS insulation can be used. 83

97 Appendix J Window rating The following graphs present rating for global warming potential, primary energy content, maintenance and disposal potential for the chosen types of windows: 1. Solid wood with insulation 2. Solid wood with insulation, filled with Krypton 3. Wood/PUR/wood with insulation 4. Wood/PUR/wood without additional insulation 5. Wood/PUR/wood with insulation, filled with Krypton 6. Wood/XPS/aluminum with additional insulation 7. Wood/XPS/aluminum without additional insulation 8. Wood/XPS/aluminum with additional insulation, filled with Krypton 9. Wood/cork/aluminum with additional insulation 10. Wood/cellulose/aluminum with additional insulation 11. PVC with additional insulation 84

98 From: Austrian Institute for Healthy and Ecological Building (2009) It is interesting to note that the solid timber and insulated timber windows have the smallest primary energy and global warming potential and are the easiest to dispose of, but their maintenance is the most demanding. In the middle of the scale are alu-clad timber windows, with middle values for energy use and difficult to dispose of, but easy to maintain. The PVC windows have the highest energy content and are difficult to dispose of, but do not require maintenance. From the environmental point of view PVC windows are the worst choice, but they are commonly the least expensive option. 85

99 Appendix K Direct solar gain strategy Direct gain is the simplest form of passive strategy. Solar energy enters through glazing and warms up a wall or a floor which will absorb, store and emit the heat. The solar gains can contribute to a net positive energy gains over a year only with the use of high performance windows. Glazing needs to have a low U-value and high g-value and the frames need to be warm and thermal bridge free. In the northern hemisphere the most of solar energy is received on a south face (with small differences within 25 deg. off due south), so the design requires large south-facing windows. Internal layout should reflect the location of the biggest windows with main living areas on the south side. Windows to the north should be the smallest possible for the daylight requirement (10%- 15% of the floor area) and that side of the house should be reserved for less frequently used rooms (stores, utility rooms, bathrooms). The area of thermal mass required to store the solar heat can be estimated by a general rule. The heavy mass elements of a thickness of about mm that receive direct irradiation should be about three times the area of the solar glazing (Kwok and Grondzik, 2011). It needs to be twice as much for elements with reflected radiation. In the example house the south-east solar collecting widows are 16.6m 2, so there would be a need of 50m 2 of directly irradiated heavy thermal mass. About 30m 2 is available on the ground floor for direct radiation (concrete floor). It would leave 20m 2 x 2 = 40m 2 that could be covered by reflected radiation. There is 30m 2 of the dense concrete external or party walls on ground floor and additional 20m 2 on first floor which would cover the requirement. To help with heat absorption, the ground floor can be a dense concrete with a dark-coloured clay tiled surface. If present, the plasterboard lining would have to be removed from external masonry walls and they could receive a plaster finish (which is also a part of the air tightness strategy). The procedure of establishing the most appropriate depth of the fixed overhang to maximize the gains in winter and block direct light in summer is described below. OVERHANG SIZING RULES: 1. Draw the wall to be shaded to scale; 2. Draw the summer sun angle (in Dublin 63 deg.) upward from the bottom of the glazing; 3. Draw the line at the winter sun angle (in Dublin 16 deg.) upward from the top edge of the glazing till it intersects with the summer sun angle line; 4. Draw the overhang the width will be determined by the summer and winter lines intersection. Overhang sizing rules. Adapted from: EREC (2000) 86

100 Appendix L ventilation strategies 1. Natural ventilation The most typically met natural ventilation strategy is based on wall inlets in the form of a hole in the wall and is supported by electrical extract fans, that remove stale or polluted air from all wet rooms (kitchens, bathrooms and utility rooms) while fresh air is drawn into the building via inlets in windows or walls (that can be humidity controlled) or simply by opening of the windows by occupants in dry rooms. Low power extract fans using DC motors are now readily available, typically saving up to 80% of the electricity required by conventional units. In the retrofit situation all extract fans should be fitted with a humidity controller and the air inlets should not be permanently open to the outside to reduce the level of uncontrolled air leakage through the vent. The single-room heat recovery ventilator can be used as an extractor fan. Its heat exchanger recovers from 60% of the heat from the outgoing air, using it to preheat the incoming replacement air. Background ventilation inlets would still be required in all other rooms (EST, 2011) 2. Whole house passive stack ventilation systems (PSV) Passive stack systems help to remove the stale air through the roof using vertical ducts. They consist of vertical series of ducts that connect wet rooms directly with the outside, through the roof. Moist air is extracted by the stack effect moist warm air is less dense than cold, dry air and so rises as well as by the effect of the wind blowing over the roof. Fresh air is replenished through background ventilators in windows or walls. The system does not require electricity, but unless the ducts are fitted with self-closing valves when ventilation is not required, it can allow escaping and slightly increasing the demand on the heating system. It is simple and not very expensive to install and operate, but drawbacks include difficulty of controlling the air change rates and the fact that they don t have the capability of recovering heat (EST, 2011). Fig. 1. Standard passive stack ventilation Humidity controlled passive stack ventilation system (hpsv) This system in principle works as PSV, but is controlled by intelligent air inlets and extracts. They respond automatically to changes in relative humidity, modulating the ventilation rate in each room to meet the need. Both extract grilles and air inlets use non electrical humiditysensitive control. Nylon strands in each unit expand or contract in response to humidity levels. 87

101 This automatically regulates the size of the air opening and varies the ventilation rate accordingly. The airflow rate responds continuously to demand, so maximising ventilation effectiveness and minimising heat loss through loss of warm indoor air. 2A. High indoor humidity, high ventilation rate. 2B. Low indoor humidity, low ventilation rate Fig. 2. Humidity controlled passive stack ventilation 3. Demand control mechanical extract ventilation This variation of the continuous mechanical extract system includes fans removing the stale humid air continuously from the wet rooms. If the humidity increases above 50% rh the fan speeds up to extract as much humid air as necessary and slows down again when humidity levels return to 50% rh. The air inlets contain a hygro-sensor, that exploits the natural tendency of materials to expand and contract with the rise and fall in airborne humidity. On this principle, polyamide bands of the sensor activate one or more shutters, thus determining the passage of the air according to the ambient relative humidity rate. The greater the level of humidity, within building, the more the shutters are opened. There are systems available where the incoming air comes through a device with a silencer and filter to ensure a clean room climate. 4. Whole house balanced mechanical ventilation with heat recovery. This system consists of extracting moist warm air from wet rooms and drawing in replacement air which is preheated by the outgoing air. As the rate of air intake matches the extract rate, there is no need to provide background ventilation when using this system. The required ventilation rate is delivered independently of weather conditions. However, where the other systems discussed above provide similar levels of energy efficiency, the improved energy efficiency benefit of a whole house balanced mechanical ventilation system will only be realised in really airtight properties. According to EST (2011) if the final air leakage rate is likely to be much less than 5m 3 /m 2 50 Pa, then significant energy efficiencies are possible with this type of system if it has a specific fan power of 1.0 W/l/s or less and a heat recovery efficiency of 85% or more. 88