Lime House, Ebbw Vale, Wales

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The two bed Lime House in Ebbw Vale, designed by bere:architects and neighbour to the Larch House, has full Passivhaus certification and CSH code 5. Ultra low cost, the Lime House follows the unfussy form of a traditional Welsh cottage: its simple, compact shape minimising the surface area from which it loses heat and reducing the insulation needed, with windows smaller than in the Larch House which do not need blinds for summer shading thus reducing their cost further.We developed and installed the first UK-produced, triple-glazed, certified Passivhaus windows with Welsh larch for the insulated frames. Most of the timber for doors, wall panels, floor slabs and roof elements is from Welsh forests and the insulation, roof tiles, staircase, stonework and solar panels were all made in Wales. The closed-panel timber frame system was developed using Welsh timber, adapting framing techniques from German PH dwellings for use with faster-growing, softer Welsh timber.
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Lime 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 - 1269 kWh/yr -
Natural gas use- 2221 kWh/yr -
Oil use- - -
LPG use- - -
Wood use- - -
Other Fuel - - -
Primary energy requirement - 83 kWh/m².yr -
Annual CO₂ emissions - 17 kg CO₂/m².yr -
Annual space heat demand - 17 kWh/m².yr -

Renewable energy

Electricity generationForecastMeasured
solar PV1636.8 kWh/yr -
Other Renewables Tech--
Electricity consumed by generation --
Primary energy requirement
offset by renewable generation
24 kWh/m².yr -
Annual CO₂ emissions
offset by renewable generation
3 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 W/m² demand


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

Project description

StageUnder construction
Start date03 May 2010
Occupation date01 April 2011
Location Ebbw Vale Blaenau Gwent  England
Build typeNew build
Building sectorPublic Residential
Property typeDetached
Construction typeSoftwood frame
Other construction typeInsulated timber frame with external lime render
Party wall constructionN/A
Floor area 69.1
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
ContractorPendragon Design & Build

Design strategies

Planned occupancy3 people
Space heating strategyA heat recovery ventilation unit ensures not only fresh air but also recovers the heat from the extraction. If additional heat is required the fresh air supply air can be warmed by the
Water heating strategySolar 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 strategy2kWp of Photovoltaics are installed.
Passive Solar strategyThe rear elevation faces South and the southern windows take advantage of the solar gains.
Space cooling strategyNatural cross and stack ventilation will ensure that the Welsh Passivhaus stays cool during the summer time.
Daylighting strategyAll habitable rooms and circulation spaces have windows providing adequate natural light. Natural lighting levels comply with the Code for Sustainable Homes.
Ventilation strategyComfort ventilation with 92% heat recovery (winter)Natural ventilation with extract only in the Summer
Airtightness strategy An intello membrane provides a continuous airtightness layer around the building. 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 program and then fed back into the Passivhaus Planning Package.
Insulation strategyExternal wall : timber frame with 225mm of glass 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 glass mineral wool insulation on top of the first floor ceiling (U-value = 0.068 W/m2K)Floor slab: 480mm of XPS insulation under the concrete slab (U-value = 0.076 W/m2K).
Other relevant retrofit strategies
Contextual informationThe house is constructed on the former Steelworks site in Ebbw Vale.

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 -