Project Description. Projected build start date 05 Apr 2010 Projected date of occupation. Low Energy Buildings

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Esther Josephine Jackson
5 years ago
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carried out to an occupied house owned by Penwith Housing Association.

ventilating technology, renewable energy and lighting and appliance usage.

conservatory which contains much of the equipment required for reducing the carbon emissions of the dwelling.

1 Project name Development of an integrated Ground / Air / Solar Heat Pump for plug in retrofit Project summary The retrofit will be carried out to an occupied house owned by Penwith Housing Association. It addresses the whole house solution by applying a comprehensive package of measures including fabric heat losses, heating and ventilating technology, renewable energy and lighting and appliance usage. It includes an innovative ground / air / solar source heat pump and the HeatPod a small prefabricated multi-purpose glazed porch / conservatory which contains much of the equipment required for reducing the carbon emissions of the dwelling. The complete package of measures builds on Penwith HAs practical knowledge of what can realistically be achieved in social housing homes and is designed to be highly replicable. Project Description Projected build start date 05 Apr 2010 Projected date of occupation Project stage Occupied Project location Sennen, Cornwall, England Energy target Retrofit for the Future Build type Refurbishment Low Energy Buildings Page 1

2 Building sector Property type Existing external wall construction Existing external wall additional information Existing party wall construction Floor area 64 m² Floor area calculation method Public Residential End Terrace Masonry Cavity The 50mm cavity has been filled with blown mineral wool Masonry cavity wall SAP Project team Organisation Project lead Client Architect Mechanical & electrical consultant(s) Energy consultant(s) Structural engineer Quantity surveyor Other consultant Contractor Penwith Housing Association Ltd Denys Stephens BA(Hons) MCIAT CEnv, Sustainability Manager, Penwith HA Penwith Housing Association Lead Designer (not architects) - Penwith HA Property Services Department John Parker B.Eng C.Eng MCIBSE FRSA, Earth Energy Engineering Ltd. John Parker B.Eng C.Eng MCIBSE FRSA, Earth Energy Engineering Ltd. Massie,Ludnow & Jenkins. Penwith HA Property Services Department Monitoring: Gerry Hargreaves Mears Ltd. Design strategies Planned occupancy Space heating strategy Water heating strategy The house is occupied by a married couple and their grown up daughter. It is expected that they will remain in occupation throughout the retrofit work and the project has been designed to make this possible. High efficiency ground source heat pump serving low temperature (45/40oC) high thermal mass two-pipe radiators. Control by progammable timeclock and zone thermostat. TRVs on bedrooms and kitchen only. High efficiency ground source heat pump serving primaries of indirect mains pressure factory insulated hot water cylinder. Timeclock controlled charging periods and storage temperature thermostat set point at 60oC. Electric immersion heater fitted for emergency use only. Low Energy Buildings Page 2

3 Fuel strategy Renewable energy generation strategy Passive solar strategy Space cooling strategy Daylighting strategy Ventilation strategy This project uses mains electricity as its main fuel with some further electricity from a PV system. Key drivers for the use of electricity are the absence of main gas in this rural location and the cost and carbon consequences of the fossil fuel alternatives oil and coal. Penwith HA has previously demonstrated in its pioneering work with ground source heat pumps that they can provide very cost effective space and water heating with very low CO2 emissions in off gas areas. Despite objections from some purists it is now widely accepted (including by government agencies) that ground source heat pumps are renewable energy systems. The key renewable component is the solar energy retrieved from the ground by the ground loop. The key feature of this project is it's innovative ground / air / solar source heat pump which achieves a 25% improvement on the performance of traditional GSHPs. The design also includes a 0.25kWp PV array for direct coupling to 12v DC fans and pumps only. HeatPod solar porch tempers incoming fresh air supply for mech. vent system. Balancing mechanical extract recovers solar gain using coil in low temp. ground loop circuit to supplement stored solar energy in ground. Mechanical vent system can be boosted to increase summer time flow rate, otherwise windows are openable. This project does not propose to alter the existing house in this respect. It is planned to replace the existing windows with new triple glazed high performance units, but these will retain patterns similar to the existing windows to avoid radical change in the appearance of the property. Owing to the relatively small size of the house it is well served by traditional windows for daylighting purposes. Controlled balanced supply and extract provides fresh air ventilation. Low Energy Buildings Page 3

4 Airtightness strategy Strategy for minimising thermal bridges Modelling strategy The project includes provision for a programme of pre and post retrofit pressure testing. From past experience of pressure testing Penwith HA properties of this era it has been found that their air tightness is better than might be expected owing to the original use of render and plaster finishes to concrete floors and block walls. The retrofit's inclusion of external wall insulation and high performance windows and doors (and careful sealing of the joints between these elements) is expected to significantly improve air tightness of the main envelope. It is intended to enhance air tightness between walls and first floor ceilings by the addition of sealed coving. There will then be further joint sealing carried out to any areas of weakness revealed by the first post-retrofit pressure test. By these means it is planned to reduce uncontrolled ventilation losses to 3 ACPH. There are three main areas of weakness in terms of thermal bridging: Window and door openings, the solid concrete ground floor and the Finlock gutters. (These consist of a pre-cast concrete cavity closer with an integral concrete gutter. They were widely used in the 1950s). In the retrofit the window and door opening detail will be changed so that window & door frames span the junction between the external insulation and external wall, eliminating cold bridging at that point. To reduce heat losses from the ground floor the external wall insulation will extend 600mm below dpc level. The thermal bridging at the Finlock gutters will be overcome by fixing a layer of insulation board with a coving internally at first floor ceiling level. With careful detailing and matching decorations this will not be intrusive and will avoid radical alteration of the Finlock gutters. Load and energy modelling carried out by NHER/SAP2005 and SAP Extension plus various load duration analysis techniques (ESIBEEP and EN :2008) to deliver full multiple source energy matching as well as the monthly energy summaries necessary for any standard gshp design. Low Energy Buildings Page 4

5 Insulation strategy Other relevant retrofit strategies Other information (constraints or opportunities influencing project design or outcomes) Penwith HA has very substantial practical experience of external wall insulation which has been used very effectively on approximately 1000 houses in its stock over a 25 year period. It is very effective in enclosing the thermal mass of a dwelling, tempering the fluctuation of internal temperatures, and when used with replacement windows and doors it significantly reduces air leakage. The innovations here are in applying external insulation to a previously cavity filled wall, doubling the traditional thickness of insulation and use of the system below ground to reduce heat losses from the solid ground floor. The system will include 100mm thick phenolic board external wall and ground floor edge insulation. The wall insulation will be complimented by high performance triple glazed windows and doors. This package will be completed with 400mm loft insulation and air pressure testing and and sealing areas of uncontrolled ventilation. It is an important feature of this project that it is designed to be applied to an occupied dwelling. It builds on Penwith HAs long experience of refurbishing and retrofitting existing homes and the knowledge that most tenants can cope with work to the outside of their home. Hence the external wall insulation, window & door replacement and the design of the HeatPod placing M&E equipment outside the dwelling. Although there will be internal work, it is kept to a minimum. This approach presents a much more achievable retrofit for large scale roll out than designs which require substantial internal alteration. This project is located in rural Cornwall only a few miles from Lands End, the most Westerly point in England. Despite being in an area of outstanding natural beauty, low incomes, unemployment and fuel poverty are common. The site of this project, in common with much of Penwith, does not have mains gas and can experience very severe weather in winter. The retrofit solution for this project, whilst entirely appropriate for replication in less demanding areas, is particularly suited to this type of environment. Low Energy Buildings Page 5

6 Energy use Fuel use by type (kwh/yr) Fuel previous forecast measured Electric Gas Oil LPG Wood wood pellets (secondary eating) Primary energy requirement & CO2 emissions Annual CO2 emissions (kg CO2/m².yr) Primary energy requirement (kwh/m².yr) previous forecast measured Renewable energy (kwh/yr) Renewables technology forecast measured Direct coupled 12v PV Energy consumed by generation Airtightness ( 50 Pascals ) Date of test Test result Pre-development airtightness 23 Mar Final airtightness - - Annual space heat demand ( kwh/m².yr ) Space heat demand Pre-development forecast measured Whole house energy calculation method Other energy calculation method Predicted heating load Other energy target(s) Other SAP2005 and SAP Extension supplemented by full load duration analysis as typified by BS EN methodology. Final design h W/m² (demand) Building services Occupancy 3 adults Low Energy Buildings Page 6

7 Space heating Hot water Ventilation Controls Cooking Lighting Appliances Renewables Strategy for minimising thermal bridges Prototype ground / air / solar source heat pump. The system utilises a Calorex ground source heat pump combined with a NIBE ventilation & heat recovery unit.. The gshp is connected to a 60m vertical ground loop installed in the rear garden. The heating system provides space heating via a wet radiator system. Mains pressure hot water cylinder heated by the main central heating system and providing all domestic hot water. Whole house ventilation system using a NIBE FLM ventilation & heat recovery unit. The system provides passive air supply to habitable rooms with mechanical extraction from the kitchen and bathroom. Standard 2 channel programmer for the space heating and hot water system. Built in induction hob and electric oven. CFLs fitted throughout the house. A++ rated fridge freezer & washing machine and LED television all supplied by Currys kw roof mounted Solar PV system and Ground / Air / Solar Source heat pump 100mm external wall insulation carefully detailed in relation to window & door openings to minimise thermal bridging. External floor edge insulation provided below ground level to reduce heat loss from concrete ground floor. Concrete 'Finlock' gutters insulated internally. Building construction Storeys 2 Volume m³ Thermal fabric area 148m² Roof description Roof U-value Walls description Walls U-value Party walls description Traditional 'cut' timber roof finished with concrete plain tiles insulated internally at ceiling level with 400mm mineral wool. Roof void ventilated with previously retrofitted tile vents. 0.13W/m² K Traditional cavity wall with two leaves of 100mm concrete blockwork and 50mm mineral wool filled cavity plastered internally and rendered externally. Retrofitted under this project with Knauf Marmorit Slimtherm 100mm external wall insulation with self coloured textured render finish. 0.15W/m² K Traditional cavity wall with two leaves of 100mm concrete blockwork and 50mm cavity plastered on both sides. Low Energy Buildings Page 7

8 Party walls U-value Floor description Floor U-value Glazed doors description Glazed doors U-value Opaque doors description Opaque doors U-value Windows description Windows U-value Windows energy transmittance (G-value) Windows light transmittance Rooflights description Rooflights light transmittance Rooflights U-value 0.00W/m² K Existing concrete floor slab with t&g boarded finish and 100mm EPS floor edge insulation 500mm deep below dpc level. 0.54W/m² K Main entrance doors (front & rear) Homesafe Regency range 'Amersham' GRP composite doors with ECO Packs 1 & 2. Note: these doors have small double glazed panels. 1.10W/m² K installed None fitted. 0.00W/m² K JELD-WEN 'Dreamvu' softwood triple glazed windows with JELD-WEN colour coated aluminium sub sills. 0.70W/m² K installed None installed 0.00W/m² K Low Energy Buildings Page 8

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Project name Gentoo Retrofit Bid 1 Project summary Refurbishment of 2no. Semi Detached houses using Passivhaus principles

http://lowenergybuildings.org.uk Project name Gentoo Retrofit Bid 1 Project summary Refurbishment of 2no. Semi Detached houses using Passivhaus principles Project Description Projected build start date