Larch House, Ebbw Vale, Wales

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The Larch House, designed by bere:architects, is the UKs first zero carbon (code 6), low cost, Certified Passivhaus, built as prototype social housing and launched at the National Eisteddfod for Wales in 2010.The three bedroom house is 1000ft above sea level in an exposed and misty hilltop location in Ebbw Vale. In spite of this, most energy needs are met by heat from the sun, occupants and appliances and the house generates as much energy from the sun, from solar thermal and photovoltaic panels as well as by glazing, as it uses for the whole year making it Zero Carbon by UK definition and showing how we can live comfortably with minimal impact on the natural world.The house achieved the UK's best air test for a free standing house with ...
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Larch House, Ebbw Vale, Wales : Project images

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CO2 emissionsPrimary energy requirement
Energy target

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 - 1644 kWh/yr -
Natural gas use- 2662 kWh/yr -
Oil use- - -
LPG use- - -
Wood use- - -
Other Fuel - - -
Primary energy requirement - 82 kWh/m².yr -
Annual CO₂ emissions - 17 kg CO₂/m².yr -
Annual space heat demand - 12.9 kWh/m².yr -

Renewable energy

Electricity generationForecastMeasured
Photovoltaics3846 kWh/yr -
Other Renewables Tech--
Electricity consumed by generation --
Primary energy requirement
offset by renewable generation
-29 kWh/m².yr -
Annual CO₂ emissions
offset by renewable generation
-9 kg CO₂/m².yr -

Calculation and targets

Whole house energy calculation method PHPP
Other whole house calculation method-
Energy target
Other energy targets-
Forecast heating load 10.7 W/m² demand


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

Project description

StageUnder construction
Start date01 March 2010
Occupation date01 August 2010
Location Ebbw Vale Blaenau Gwent  Wales
Build typeNew build
Building sectorPublic Residential
Property typeDetached
Construction typeOther
Other construction typeTimber frame construction
Party wall construction
Floor area 87
Floor area calculation method Treated Floor Area (PHPP)
Building certification  Passivhaus certified building Passivhaus certified building

Project Team

Project lead personbere:architects
Landlord or ClientUnited Welsh Housing Association
Mechanical & electrical consultant Alan Clarke
Energy consultantRob McLeod (BRE)
Structural engineerBob Johnson
Quantity surveyore-Griffin Consulting

Design strategies

Planned occupancy4 - 5 people
Space heating strategyA heat recovery ventilation ensures not only fresh air but also recovers the heat from the extraction. Additionally if needed there are two towel radiators installed in each bathroom.
Water heating strategyA solar thermal is in place to heat the domestic hot water. There is a gas condensing boiler for back up.
Fuel strategyMains gas. Mains electricity
Renewable energy strategy2.52kWp of Photovoltaics are installed.
Passive Solar strategyThe rear elevation faces South and the large southern elevation to maximise solar gains.
Space cooling strategyNatural cross and stack ventilation will ensure that the Welsh Passivhaus stays cool during the summer time.
Daylighting strategyThe Welsh Passivhaus benefits from large window openings. The house is shallow enough to maximise day-lighting. The kitchen achieves a minimum average daylight factor of at least 2% and the living rooms achieve average daylight factor of at least 1.5%
Ventilation strategyComfort ventilation with 92% heat recovery (winter)Natural ventilation with extract only in the Summer
Airtightness strategy OSB with taped joints and an intello membrane. Passivhaus detailing around windows and other openings. Particular care and supervision of M&E penetrations. Careful detailing and site supervision.Preliminary testing to help site identify air leakage routes.
Strategy for minimising thermal bridges Bridge-free construction throughout and all junctions have been modelled in Heat2 and the results fed into the PHPP.
Modelling strategyEvery junction of the building was optimised using a thermal modelling programm and then fed back into the Passivhaus Planning Package.
Insulation strategyExternal wall : timber frame with 280mm of mineral wool insulation in between the studs, with a 100mm service void on the inside with wood fibre insulation and a 100mm rigid wood fibre insulation layer on the outside (U-value = 0.095 W/m2K)Roof: 560mm of mineral wool insulation on top of the first floor ceiling (U-value = 0.074 W/m2K)Floor slab: 480mm of EPS insulation under the concrete slab (U-value = 0.076 W/m2K).
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 -