Hounslow Council Passivhaus Retrofit - and the development of a decision making matrix
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as PDF The house is a 3-bedroom semi-detached single-family dwelling built in the early 1950s. The property is located in Hounslow close to Heathrow airport, and is not located within a conservation area. We propose a Passivhaus refurbishment including external insulation, roof insulation, triple glazed windows and heat recovery ventilation. German best practice techniques in low-energy building design, as evolved by the Passivhaus Institute in Darmstadt, have kick-started a revolution in construction practices. Frequently achieving a remarkable Factor-10 reduction in typical space heating energy demand, Passivhaus success is contingent upon using a whole-house approach.
Retrofit for the future ZA522P
Hounslow Council Passivhaus Retrofit - and the development of a decision making matrix : 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 | 2795 kWh/yr | 1592 kWh/yr | - |
|---|---|---|---|
| Natural gas use | 55234 kWh/yr | 2923 kWh/yr | - |
| Oil use | - | - | - |
| LPG use | - | - | - |
| Wood use | - | - | - |
| Other Fuel | - | - | - |
| Pre-development | Forecast | Measured | |
| Primary energy requirement | 837 kWh/m².yr | 87 kWh/m².yr | - |
|---|---|---|---|
| Annual CO₂ emissions | 155 kg CO₂/m².yr | 18 kg CO₂/m².yr | - |
| Annual space heat demand | - | 23 kWh/m².yr | - |
Renewable energy
| Electricity generation | Forecast | Measured |
|---|---|---|
| Renewables Technology | - | - |
| Other Renewables Tech | - | - |
| Electricity consumed by generation | - | - |
| Primary energy requirement offset by renewable generation | 87 kWh/m².yr | - |
| Annual CO₂ emissions offset by renewable generation | 18 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 | Air tightness target 0.6h-1 (air changes per hour) |
| Forecast heating load | 12 W/m² demand |
Airtightness
| Date | Result | |
| Pre-development air permeability test | - | 7.06m³/m².hr @ 50 Pascals |
|---|---|---|
| Final air permeability test | - | 1.39m³/m².hr @ 50 Pascals |
Project description
| Stage | Under construction |
|---|---|
| Start date | 02 August 2010 |
| Occupation date | 03 December 2010 |
| Location | London London England |
| Build type | Refurbishment |
| Building sector | Public Residential |
| Property type | Semi-Detached |
| Construction type | Solid Brick |
| Other construction type | Solid brick with pebbledash render |
| Party wall construction | Solid brick |
| Floor area | 84.23 m² |
| Floor area calculation method | Treated Floor Area (PHPP) |
| Building certification |
Project Team
| Organisation | Bere Associates Limited |
|---|---|
| Project lead person | bere:architects |
| Landlord or Client | Hounslow Homes |
| Architect | bere:architects |
| Mechanical & electrical consultant | Alan Clarke Energy Consultant and Building Services Engineer |
| Energy consultant | Alan Clarke Energy Consultant and Building Services Engineer |
| Structural engineer | Rodrigues Associates |
| Quantity surveyor | e-Griffin Consulting |
| Consultant | |
| Contractor | Not yet selected |
Design strategies
| Planned occupancy | 3 people |
|---|---|
| Space heating strategy | To use existing radiator system. New boiler to be Viessmann storage combi with 250 litres of storage for use with solar panels. The unit is compact and can fit in the kitchen, and provides all heating and hot water services in one pre-plumbed and configured unit for rapid installation. |
| Water heating strategy | The Viessmann unit has built in solar hot water heat exchanger, pump and controls, for quick connection to roof mounted solar hot water panels. These are estimated to provide 70% of hot water requirement. the location of the hot water storage in the kitchen enables very short deadlegs to the kitchen tap and the bathroom on the first floor, minimising wastage of hot water. |
| Fuel strategy | Mains gas and electricity, as existing. |
| Renewable energy strategy | None |
| Passive Solar strategy | Passive solar gains are constrained by working with existing window openings. |
| Space cooling strategy | The mechanical ventilation system has controls that provide for automatic summer bypass of the heat exchanger, depending on temperature, so free-cooling, including night cooling, can be provided. This enables cooling and ventilation to be provided without opening windows if desired for sound insulation. The automatic controls also switch back to using the heat exchanger if external temperature is above internal. |
| Daylighting strategy | Existing daylighting is good, and window areas are maintained. |
| Ventilation strategy | Whole house ventilation with passivhaus mechanical heat recovery ventilation unit. This is located in the warm loft, because of space constraints in the house, with supply and extract ductwork able to use the loft space for distribution. |
| Airtightness strategy | Preliminary testing to help site identify air leakage routes. External air barrier on walls joining over-rafter barrier in recovered roof. windows sealed to external face of wall. Services penetrations sealed at the air barrier. Passivhaus detailing around windows and other openings. Particular care and supervision of M&E penetrations. Careful detailing and site supervision. |
| Strategy for minimising thermal bridges | External insulation to be continuous over walls, and roof insulation extended over rafters to be continuous with wall insulation at eaves. Below ground perimeter insulation at base of wall to address thermal bridge here. |
| Modelling strategy | PHPP for energy and summer overheating Heat for thermal bridging |
| Insulation strategy | External 300mm polystyrene system with render over (the house is currently rendered) to give U-value of 0.095 Roof insulation 300mm mineral fibre and 100mm wood fibre to give U-value 0.11 Floor insulation 200mm below relaid floor slab/screed Passivhaus windows overall U=0.8 |
| Other relevant retrofit strategies | The current occupants remain in the house. Disturbance to be kept to a minimum, though they need to move out for insulation to the floor. |
| Contextual information | We have had a meeting with Houslow Planning department, the planning department supports the broad aims of the project and welcome the benefits it will bring to our residents. It is great that we are one of the pilot Councils for the project. As discussed, the works will require planning consent given the thickness of the insulation that is usually required and the resultant alteration to the house(s). In cases such as (this), where there are no key features in the street scene or the individual house and there are no conservation area restrictions, the planning consent process should be fairly straightforward. |
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 |