Retrofit to Cottages, Warlingham, Surrey
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as PDF An innovative combination of internal and external insulation with airtighting will reduce demand on a very hard to treat house. A solar gain heat pump will provide the remaining energy demand, and a PV array will give additional electricity production. The solution has been designed to be rugged and long-lived, and nearly all measures are maintenance-free. The solar gain heat pump is the only possible exception, and this will act as a closely monitored UK trial of the technology (which is widely used elsewhere in Europe). Emphasis has been placed on minimal disruption to the tenant, who will remain in-situ throughout the works.
Retrofit for the future ZA606E
Retrofit to Cottages, Warlingham, Surrey : Project images
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Energy and fuel use
Measured data from renewable generation is not yet available.
Fuel use
| Pre-development | Forecast | Measured | |
| Electricity use | 43050 kWh/yr | 3420.6 kWh/yr | - |
|---|---|---|---|
| Natural gas use | - | - | - |
| Oil use | - | - | - |
| LPG use | - | - | - |
| Wood use | - | - | - |
| Other Fuel | - | - | - |
| Pre-development | Forecast | Measured | |
| Primary energy requirement | 1472 kWh/m².yr | 117 kWh/m².yr | - |
|---|---|---|---|
| Annual CO₂ emissions | 348 kg CO₂/m².yr | 28 kg CO₂/m².yr | - |
| Annual space heat demand | - | 58 kWh/m².yr | - |
Renewable energy
| Electricity generation | Forecast | Measured |
|---|---|---|
| Photovoltaic array | 1029 kWh/yr | - |
| Other Renewables Tech | - | - |
| Electricity consumed by generation | - | - |
| Primary energy requirement offset by renewable generation | 82 kWh/m².yr | - |
| Annual CO₂ emissions offset by renewable generation | 20 kg CO₂/m².yr | - |
Calculation and targets
| Whole house energy calculation method | PHPP |
|---|---|
| Other whole house calculation method | - |
| Energy target | Retrofit for the Future |
| Other energy targets | - |
| Forecast heating load | 31.3 W/m² demand |
Airtightness
| Date | Result | |
| Pre-development air permeability test | - | 5.58m³/m².hr @ 50 Pascals |
|---|---|---|
| Final air permeability test | - | 4.01m³/m².hr @ 50 Pascals |
Project description
| Stage | Under construction |
|---|---|
| Start date | 01 May 2010 |
| Occupation date | 01 July 2010 |
| Location | Warlingham Surrey England |
| Build type | Refurbishment |
| Building sector | Public Residential |
| Property type | Semi-Detached |
| Construction type | Solid Brick |
| Other construction type | 225mm thickness |
| Party wall construction | 225mm solid brick |
| Floor area | 73.1 m² |
| Floor area calculation method | Treated Floor Area (PHPP) |
| Building certification |
Project Team
| Organisation | CEN Services Ltd. |
|---|---|
| Project lead person | CEN Services Ltd |
| Landlord or Client | Croydon Council |
| Architect | |
| Mechanical & electrical consultant | Bryant and Reina |
| Energy consultant | CEN Services Ltd |
| Structural engineer | |
| Quantity surveyor | |
| Consultant | |
| Contractor | Jenner Construction |
Design strategies
| Planned occupancy | One elderly lady, in the house most days. |
|---|---|
| Space heating strategy | Solar gain heat pump feeding low temperature system, with underfloor heating on the ground floor and radiators on first floor. |
| Water heating strategy | Solar gain heat pump. |
| Fuel strategy | Mains electricity. |
| Renewable energy strategy | 1.225 kWp solar photovoltaic array to be installed. Predicted output is 1029 kWh/year. |
| Passive Solar strategy | South-facing conservatory to be constructed, to maximise solar gains. In winter it will be isolated from the rest of the house. No north-facing glazing. |
| Space cooling strategy | Natural ventilation, controlled by opening windows. Porch will be isolated from the rest of the house in summer, to reduce overheating potential. External wall insulation will keep significant thermal mass within the building, smoothing temperature peaks and allowing night cooling. |
| Daylighting strategy | Windows will be moved outwards, reducing reveals and hence reducing shading. |
| Ventilation strategy | Natural ventilation, with mechanical boost when necessary. Controlled by opening windows, so the tenant's behaviour is not restricted. |
| Airtightness strategy | Floors overlaid with an airtight insulation and heating system, and seals made at the skirting boards. External wall insulation will be directly sealed to the ceiling insulation and external membrane, to provide a continuous barrier. The front wall will be covered with airtight plaster, sealed at the sides and ceiling. Careful seals made at every hole in the building fabric, e.g. for cables and pipes. |
| Strategy for minimising thermal bridges | Continuous external insulation around the side and rear of the property, extending down well below the floor level (some excavation will be required). Internal insulation will be "wrapped" along the side walls and ceiling, at least a metre in each direction, to reduce thermal bridges at the junction. Windows and doors will be installed according to best practice for thermal bridge-free construction. |
| Modelling strategy | Whole house modelling was undertaken using PHPP and the SAP Whole House extension. Additional use was made of THERM to analyse thermal bridges and PVSYST to predict output from the PV array. |
| Insulation strategy | Application of external insulation to side and rear solid walls, to give U = 0.15W/m2K. Application of internal insulation to front wall, to give U = 0.35 W/m2K. Phenolic insulation between and under joists in loft, to give U = 0.1 W/m2K. Phenolic insulation between joists and aerogel interior insulation on sloping ceilings, to give U = 0.17 W/m2K. Vacuum insulated panels, overlaid with underfloor heating, installed on both timber and concrete floors, to give U = 0.17 W/m2K. |
| Other relevant retrofit strategies | These works will be carried out with the tenant in-situ. Using a careful works programme, the disruption to the tenant can be minimised. This will provide an opportunity to test the performance within the UK of the solar gain heat pump. It also serves as a useful comparison of different insulation types, and an analysis of how they can work together. |
| Contextual information | Planning constraints have led to a decision not to insulate the front wall externally, despite the challenges with thermal bridges that this presented. The old age of the tenant makes this work a priority, and means that minimising disruption during the works is essential. |
Building services
| Occupancy | NULL |
|---|---|
| Space heating | NULL |
| Hot water | NULL |
| Ventilation | NULL |
| Controls | NULL |
| Cooking | NULL |
| Lighting | NULL |
| Appliances | NULL |
| Renewable energy generation system | NULL |
| Strategy for minimising thermal bridges | NULL |
Building construction
| Storeys | |
|---|---|
| Volume | - |
| Thermal fabric area | - |
| Roof description | NULL |
| Roof U-value | 0.00 W/m² K |
| Walls description | NULL |
| Walls U-value | 0.00 W/m² K |
| Party walls description | NULL |
| Party walls U-value | 0.00 W/m² K |
| Floor description | NULL |
| Floor U-value | 0.00 W/m² K |
| Glazed doors description | NULL |
| Glazed doors U-value | 0.00 W/m² K - |
| Opaque doors description | NULL |
| Opaque doors U-value | 0.00 W/m² K - |
| Windows description | NULL |
| Windows U-value | 0.00 W/m² K - |
| Windows energy transmittance (G-value) | - |
| Windows light transmittance | - |
| Rooflights description | NULL |
| Rooflights light transmittance | - |
| Rooflights U-value | 0.00 W/m² K |