LCA and Design for Optimising a House In Sydney: Exploring how LCA interfaces with designers and building occupants

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1 LCA and Design for Optimising a House In Sydney: Exploring how LCA interfaces with designers and building occupants Murray Hall 1 and Peter Poulet 2 1. Life Cycle Design, now working at CSIRO; 2. NSW Government Architect s Office URL: Murray.Hall@csiro.au ABSTRACT This paper presents a recent case study of building design and LCA. It explores the use of LCA in the design stage as well as assessing the performance of the design. The main LCA practitioner was also the co-designer and provides insight into the application of life cycle thinking in design. The designs also drew upon architectural science with the aim of being 'free running' naturally ventilated buildings. The building design process, building design and performance is presented in terms of LCA as well as thermal comfort. The variability of design performance during operation is explored and the use of scenarios discussed in relation to emerging ISO standards for LCA of buildings and building materials. Keywords: Life Cycle Assessment, Residential buildings, Design, ISO Standards, Sustainability 1. INTRODUCTION This paper draws upon two reports commissioned by the Cement Concrete Aggregates Australia. The first report focussed on the life cycle assessment of a typical mass market house in Sydney. The second study sought to optimise this performance through passive solar design and to provide a comparison. An important aim of the study was to investigate the relative importance of embodied and operational performance and the role of materials in both areas. It also performed detailed thermal assessment to ensure building design and operation could be justified in terms of thermal comfort. However, the study also revealed other issues for life cycle assessment of buildings and these are discussed in context of developing standards of ISO/DIS Sustainability in building construction -- Environmental declaration of building products (ISO 21930) and ISO/TS :2006 Sustainability in building construction -- Framework for methods of assessment for environmental performance of construction works -- Part 1: Buildings (ISO 21931). In addition, insights were gained in the role of life cycle assessment information and the design process, which is further developed examining the interface between life cycle assessment and user scenarios. 2. ASSUMPTIONS The basic assumptions for the study are detailed below. The assumptions were the same for both case studies to allow comparison. The limitations of these assumptions including data quality are considered in the discussion. Building Assumptions: Building Type: Residential Life Cycle: 50 years (varied as discussed in the results) No. occupants: 4 Total annual heating and cooling load: dependent upon energy modelling for the case study (because assumed to operate in passive mode) Energy for other purposes: General case of 7500 kwh and Green case of 2882 kwh ** 5 th Australian Conference on Life Cycle Assessment Achieving business benefits from managing life cycle impacts Melbourne, November

2 Construction waste: sorted and recycled Operational waste: sorted and recycled Operational waste per occupant per year to landfill: 349 kg Operational waste per occupant per year recycled/reused: 125 kg Water monitoring*: no Water Responsibility Plan*: no Water fixtures: 9/4L toilet, 15 L/min showers, 9 L/min taps, manual flow taps, manual flow urinal Evaporative air cooling: no Landscape irrigation*: 0 m2 * The water calculation in LCAid was developed in consultation with the hydraulics group of the NSW Department of Public Works and Services. These factors were identified as determinants for the amount of water used based upon the Department s water engineering and management experience. ** The energy assumptions were based upon information from a previous study and used for consistency in the comparisons. However, it later became apparent that this assumption had a large influence on the results and requires more detailed analysis. The study was performed using the software LCAid. This software uses a Life Cycle Inventory developed by the NSW Department of Commerce, with data collection in part generated by the requirements of the Sydney 2000 Olympic Games. The data is largely focussed on construction materials and is characterised using Eco Indicator 95 (Goedkoop 1995) with additional categories added for water and waste. LCAid contains a water calculation module for building operation based on type of fixtures, landscaping, soil type and the climate of the region. Waste defaults are based upon average waste in NSW from audits by the Sydney Waste Boards which were retained for this study (DPWS 2001). Thermal comfort was considered in conventional terms. This has since evolved through adaptive comfort such as ASHRAE and is discussed in terms of the LCA results in the discussion. 3. RESULTS The focus of the results in this section is on the comparison of the performance of the two case studies as well as identifying the stage of the life cycle that dominates the results for a particular indicator. The following Fig. 1. illustrates the re-designed mass market house. The same floor area, functionality and general appearance was retained to illustrate that improved environmental performance can easily conform to the existing suburban aesthetic. Fig. 1. Re-design of Mass Market House for Passive Solar and Water Efficiency

3 Another important feature of the house was to use landscaping to minimise water use and create a micro climate to improve thermal comfort for the house. The use of local native vegetation was assumed to reduce the need for watering as noted in the assumptions which were part of the water calculation in LCAid. Fig. 2 Landscaping for Reduced Water Use and Micro climate The following figure illustrates the comparison of the various construction assemblies considered for the redesigned house. The LCA indicator results for the house performance for the various construction assemblies were very similar. Analysis of each indicator showed that the greatest contributor to the indicators of Greenhouse Effect, Energy Use, Nutriphication, Acidification, Summer Smog and Winter Smog was electricity use. Carcinogenesis and heavy metals were linked to the steel roof in option 2A as well as the Aluminium windows. The significance of this result is questionable and without impact assessment in the results it remains an area for further investigation. In addition, the method of presentation expresses the relative difference of the results to the benchmark and the physical quantity of emissions is small. Of interest is the affect of maintenance for these results, essentially doubling the effect of the initial installation for some materials such as the steel roof over the life cycle. Other impacts such as waste and water were very similar for each case study and are discussed in more detail below.

4 Table 1. Construction Assemblies Considered in the Optimised Sydney Residential House Case study Fig. 3. Life Cycle Inventory results expressed relative to the case study benchmark

5 The following figure shows the contribution of each stage of the life cycle to the indicator. Fig 4. Contribution of Life Cycle Stage for each indicator Operation dominates the indicators associated with energy and water as noted above. The life cycle stages from waste show that operation and demolition are both approximately 45% of the life cycle results for the house while production of the materials and construction is about 10%. This result depends partly upon the classification of wastes. Overburden and waste rock from ore processing was not included and can be many time the mass of the final product. If included this waste would dominate the results and be many times the demolition waste (which reflects the mass of the final products). This waste stream could be reported separately to indicate impacts such as land disturbance whereas the waste category used for the results is more reflective of resource waste and landfill impacts. Other impacts categories were associated with particular materials as noted above. 3.1 Comparison of the Two Studies The main difference between the re-design and the mass market house in terms of performance relate to water and landscaping. Over a fifty year life cycle the redesigned house used approximately 60% of the water required by the mass market house. This result is indicative only but suggests that areas such as water efficient landscaping can dramatically improve residential water consumption. The re-designed house also improved thermal performance and justified a free running building in the Sydney climate. The best performing design for thermal comfort had high thermal mass on the interior of the building, which stored heat during winter and stabilised temperatures during summer. Approximately 80% of time in each zone was within a comfort band of o C. The thermal modelling was performed by Steensen Varming Pty Ltd using the TAS software. The following Fig. 5 shows the thermal performance in terms of comfort bands for the various construction

6 types considered. Significantly, if thermal mass is not used to capture heat during winter or is not insulated, then the benefits to thermal comfort are lost, illustrating that the performance of the materials is dependent upon the design. Fig. 5 Thermal Comfort Modelling for the Living/Dining Zone of the Optimised Sydney House However, although heating and cooling energy was largely eliminated in the redesigned house, the change in greenhouse and other energy emissions was not as large as might be expected. This was because heating and cooling energy is not the main energy use for the average house in Sydney. The change was in the order of a 20% reduction in greenhouse emissions, although this is dependent on type of fuels for heating and other assumptions for average household energy. For example, Fay et al (2000) notes that approximately half of the energy used in a house in Victoria is for space heating. However, if this heating is produced from gas then the greenhouse gas emissions will be significantly less than may be expected from the proportion of energy use. The following Fig. illustrates the greenhouse gas emissions for an average Australian residence. Fig. 6 Breakdown of Greenhouse Emission for the Average Australian Household (Your Home Guide Technical Manual Fact Sheet 40, 4.4 Energy Use Introduction based upon AGO 1999) Transport is not included in the above figure and can be in the order of an additional 60% of the household emission categories reported above (The Mooreland Energy Foundation 200?). In addition, understanding what constitutes the

7 average household needs to consider the diversity of practices that can be hidden in the average. For example, excluding transport, hot water heating systems are on average the main use of energy for most households. However, a solar hot water system with a gas booster produces only a fraction of the greenhouse gas emissions of an electric hot water system. Because the majority of households (62%) use electric hot water systems while only 5% use solar hot water systems, the household average reflects the electric hot water greenhouse emissions (Australian Bureau of Statistics accessed 23 Dec 2005b). Although not a particularly creative part of the design process, the use of a solar hot water system for a residential house can be one of the most effective ways to improve greenhouse gas emissions for the average Australian house. 4. DISCUSSION The focus of this discussion is the interface between LCA results and their application to improve building performance. The quantitative LCA results provide useful information for the design process. However, to translate into a design action, the technical information must combine with a practical understanding of buildings and the design process. Flyvbjerg (2001) refers to practical knowledge, called phronesis, which provides the basis for action in a social context. In a similar vein, Guy (2000) highlights how technical knowledge is often well developed, such as that for insulation to improve building performance, but can fail to be implemented due to poor understanding of the social context. Although the following discussion does not explore social science theories, the notion of practical knowledge is used as a framework for considering how LCA results might be used to improve performance. This is discussed using the case studies and possible applications of the emerging ISO Standards for Sustainability in Building and Construction. 4.1 Data Issues for Residential Buildings The LCA data was used in this project to identify the relative importance of impacts in different stages of the life cycle, in particular the role of thermal mass materials. In the design process, discussed below, this was important to focus the attention on areas of large impact in the life cycle (a similar approach is suggested by Grant et al (2002)). The truncations errors in process calculations can become relatively small over the life cycle for the indicators considered if construction materials are a minor stage of the life cycle 1. A change of indicators, such as land impacts, may make construction stage impacts a larger part of the life cycle and require greater focus on the data. For energy related impacts, the relative proportion of life cycle impacts in this study appear to be similar to those calculated for a Melbourne house using input-output data (Fay et al 2000). Fay et al (2000) presents a life cycle energy analysis of a Melbourne residential house and reports energy for construction and maintenance of about 30% and operating (for a thermally efficient house) of amount 70% over a 50 year life cycle. Another case study of a Sydney house (BHP 2000) includes fit out, appliances and maintenance using process LCA calculations and reports construction as about 5% of the total energy used. All of these case studies have vastly different assumptions over what is included in the analysis. For example, BHP (2000) includes an electric hot water system that uses over half of the electricity to operate the house and the total household energy also includes the fuel for the lawnmower. Although the general importance of operation is clear from each case study, the differing assumptions suggest that the use scenario is currently a greater source of difference than the LCA method of calculating the data. Assumptions for user behaviour are also important for defining how a design can affect performance. For example, constant renovations or replacement of materials before the end of their service life will change the impact of materials used during operation. In terms of the design process, this can be challenging and user behaviour can be contrary to the design intent (as discussed below in the design process). Nonetheless, detail on the use scenario can open pathways to improve the actual performance of the design in operation. This also highlights the limitations of this study for considerations beyond its aim i.e. to understand the relationship of concrete materials to the life cycle of the house. A study aiming to quantify the full impact of a residential house would also need to consider factors such as fittings, detailed maintenance, renovations, the location of the house for transportation purposes and user behaviour. 4.2 LCA input to the design process In the design process for this project and others using LCAid by the NSW Government Architect, the presentation of LCA information has been most useful when interpreted as a building design action and used to illustrate the type of improvement in performance. The architect is limited in time and often not well positioned to translate the LCA results 1 For example, if the construction stage represents only 20% of the life cycle impact, then a 50% error in process data for construction would only change the life cycle results by about 10%.

8 into a design response, to consider tradeoffs in impacts, or to fully understand what actions would give the greatest improvement in performance. The need to translate the results into design direction was further highlighted by the difficulty of interpreting some indicators and the qualifications placed upon their meaning in the Australian context, including carcinogenesis and some air pollution indicators. The architect was most effective when briefed on strategic areas of the design with creative effort focussed on clear targets. The most important issues need to be considered in the early stages of design, a notion of the Pareto approach which is captured in emerging ISO standards for buildings. 4.3 Scenarios and ISO and The above discussion of factors such as home renovations and the location of the household present a challenge to the designer. In most cases the designer will have little control over the location, and minor, if any input into how the building is operated and renovated. It was also noted in section 4.1 that the user behaviour can have a large effect on the LCA results. This suggests that scenarios for performance should be based on current trends unless there is some particular design action that will require a particular use. For example, this challenge is apparent for passive solar design in climates where the use of air conditioning has become expected. This presents a risk that a passive designed house will be retrofitted for air conditioning over the course of its life and consume more heating and cooling energy than a house designed for air conditioning. Ironically, this coincides with recognition of user influence over the perception of thermal comfort. ASHRAE Standard recognises that part of the perception of thermal comfort is empirically related to adaptation to a climate and personal control over building operation (ASHRAE ). Use scenarios also have implications for Environmental Product Declarations (EPD). The developing ISO requires that an EPD of a building material for comparison consider the full life cycle of the building. The case studies presented illustrated the relationship of thermal mass building materials to comfort and heating and cooling loads. The performance of the material was dependent upon the design and climate and site context. A building project that does not aim or does not have a site or climate to capture this potential cannot use a scenario that suggests an improved performance for the EPD. ISO also suggests the importance of the management of the materials during its life cycle. For example, a material producer could justify a scenario with improved use performance as part of the EPD if supported by a product stewardship process that demonstrates improvement. Although the inclusion of the full life cycle and scenarios presents a challenge for simply using existing LCI data for a building product declaration, it also provides a potential pathway for improvement beyond the limitations of the adversarial approach of product claim against product claim. 4.4 Implications for indicators The case study presented used the required indicators outlined in the developing ISO standard. This currently includes the Eco Indicator 95 categories supplemented by energy, water and waste. However, impacts from building materials on biodiversity and the implications of house location on transport energy and air pollution indicators was not considered in this study. The issue of house location is perhaps more related to planning than a design decision, yet it does provide a context for the importance of air pollution indicators presented as part of Eco Indicator 95. For example, air pollutants in Sydney such as ozone are largely attributed to vehicle use and not materials production (DEC 2005). The affect of the materials on Indoor Air Quality (IAQ) was also missing in this study but is an issue captured in emerging ISO standards for buildings. As noted by Peuportier (2001) regarding an LCA study of a French house, the indoor emissions may have a much greater effect on human health than diluted external emissions associated with the building life cycle (perhaps with the exception of occupant transport, which was not included in the study). The link between building materials to human health and productivity also provides an important link to the financial case for sustainable buildings. 5. REFERENCES 1. ASHRAE (2004) Thermal Environmental Conditions for Human Occupancy American Society of Heating, Refrigerating and Air Conditioning Engineers 2. Australian Bureau of Statistics accessed 23 Dec 2005a Australian Social Trends 1998 People & the Environment - Use of Resources: Household energy use 3. Australian Bureau of Statistics accessed 23 Dec 2005b Australian Social Trends 1997 Housing - Housing & Lifestyle: Environment & the home BHP (2000) AV Jennings Casestudy,

9 4. DEC (2005) Air Pollution Economics: Health Costs of Air Pollution in the Greater Sydney Metropolitan Region. NSW Department of Environment and Conservation 5. DPWS (2001) LCAid. Software produced by the NSW Department of Public Works and Services (NSW Department of Commerce) 6. Fay, R., Treloar, G., Iyer-Raniga, U. (2000) Life Cycle Energy Analysis of Buildings: a case study Building Research and Information (2000) 28(1), 31-41, E & FN Spon 7. Flyvbjerg, B. (2001) Making Social Science Matter: Why social inquiry fails and how it can succeed again. University Press, Cambridge 8. Goedkoop, M. (1995) The Eco-indicator 95, Final Report National Reuse of Waste Research Programme (NOH). ISBN Guy, S., Shove, E. (2000) The Sociology of Energy, Buildings and the Environment: Constructing knowledge, designing practice. Routledge, London 10. Grant, T., Hes, D. (2002) Life Cycle Assessment Application in Buildings GEN 51. BDP Environment Design Guide, Royal Australian Institute of Architects. 11. ISO/TS :2006 Sustainability in building construction -- Sustainability indicators -- Part 1: Framework for development of indicators for buildings 12. ISO/TS :2006 Sustainability in building construction -- Framework for methods of assessment for environmental performance of construction works -- Part 1: Buildings 13. ISO/DIS Sustainability in building construction -- Environmental declaration of building products 14. Moreland Energy Foundation Ltd (200?) Home Greenhouse Audit Manual Cool Communities 15. Peuportier, B. (2001) Life cycle assessment applied to the comparative evaluation of single family houses in the French context Energy and Buildings 33 (2001) , Elsevier