Hounslow Passivhaus Retrofit

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This social housing retrofit by bere:architects, will be Enerphit passivhaus making use of external insulation, new windows, and heat recovery ventilation to ensure fresh air at the same time as very low heat loss. Specific heat energy requirements will be reduced by 95%, while alsominimizing primary energy use. The existing property has an abnormally high energy demand asassessed using the Passivhaus Planning Package (PHPP). These large values are in part due to a complete absence of loft insulation. The main objectives of the project are to show that deepenergy cuts are possible with social housing stock. As UK exposure to and experience of Passivhaus grows, we aim to show that improved thermal comfort, reduced energy bills and lower CO2 emissions are possible for millions of people in existing houses.
Images Graphs Figures Description Strategies Building

Hounslow Passivhaus Retrofit : Project images

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CO2 emissionsPrimary energy requirement
Energy target
Retrofit for the Future

Energy and fuel use

Fuel use by type
Primary energy requirement
CO2 emissions

Measured data from renewable generation is not yet available.

Fuel use

Electricity use 2728 kWh/yr 1591 kWh/yr -
Natural gas use45658 kWh/yr 2859 kWh/yr -
Oil use- - -
LPG use- - -
Wood use- - -
Other Fuel - - -
Primary energy requirement 705 kWh/m².yr 86 kWh/m².yr -
Annual CO₂ emissions 131 kg CO₂/m².yr 18 kg CO₂/m².yr -
Annual space heat demand 401 kWh/m².yr 22 kWh/m².yr -

Renewable energy

Electricity generationForecastMeasured
Renewables Technology--
Other Renewables Tech--
Electricity consumed by generation --
Primary energy requirement
offset by renewable generation
86 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-
Forecast heating load 12 W/m² demand


Pre-development air permeability test--
Final air permeability test--

Project description

StageUnder construction
Start date15 September 2010
Occupation date
Location London   England
Build typeRefurbishment
Building sectorPublic Residential
Property typeSemi-Detached
Construction typeSolid Brick
Other construction type230mm thick
Party wall construction230mm solid brick
Floor area 84.2
Floor area calculation method Treated Floor Area (PHPP)
Building certification

Project Team

Project lead personbere:architects
Landlord or ClientSouthern Housing
Mechanical & electrical consultant Alan Clarke
Energy consultantAlan Clarke
Structural engineerGalbraith Hunt Pennington
Quantity surveyore Griffin Consulting

Design strategies

Planned occupancyTwo People
Space heating strategyHeated through the air with mechanical heat recovery ventilation.
Water heating strategySolar hot water (with gas condensating boiler top up)
Fuel strategyMains Gas.
Renewable energy strategySolar thermal
Passive Solar strategySolar thermal
Space cooling strategyNatural ventilation - cross ventilation
Daylighting strategy
Ventilation strategyMechanical heat recovery ventilation (winter) and natural ventilation (summer).
Airtightness strategy Airtight details
Strategy for minimising thermal bridges Continuity of insulation including exterior insulation, loft insulation and underfloor insulation of entire structural zone.
Modelling strategyHeat 2 and Passivhaus Planning package (PHPP)
Insulation strategy300mm exterior and loft insulation. 150mm of insulation in suspended floor.
Other relevant retrofit strategies
Contextual information

Building services

Space heating
Hot water
Renewable energy generation system
Strategy for minimising thermal bridges

Building construction

Volume -
Thermal fabric area -
Roof description
Roof U-value -
Walls description
Walls U-value -
Party walls description
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 -