Y Foel

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Y foel is the first building in the United Kingdom to achieve passivhaus certification. It is a self-build private house in Wales with visionary owners who commissioned JPW Construction to achieve passivhaus certification. The property is 2 or 3 bedroom.The construction is an external I beam timber frame with an internal core of earth block walls in the ground floor only, with Welsh slate floor slabs on 60% GGBS (ground granulated blastfurnace slag) in situ slab. The wall panels were fabricated on the in-situ slab on site and pivoted into position as the house has limited access. I beam A-frame roof trusses were built on site and lifted individually. By reducing the number of individual panels thermal bridging was also reduced at panel joins.
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Y Foel : 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 - - -
Natural gas use- - -
Oil use- - -
LPG use- - -
Wood use- - -
Other Fuel - - -
Primary energy requirement - - -
Annual CO₂ emissions - - -
Annual space heat demand - - -

Renewable energy

Electricity generationForecastMeasured
Renewables Technology--
Other Renewables Tech--
Electricity consumed by generation --
Primary energy requirement
offset by renewable generation
Annual CO₂ emissions
offset by renewable generation

Calculation and targets

Whole house energy calculation method
Other whole house calculation method-
Energy target PassivHaus
Other energy targets-
Forecast heating load -


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

Project description

Start date01 April 2005
Occupation date09 September 2009
Location Machynlleth Powys  Wales
Build typeNew build
Building sectorPrivate Residential
Property typeDetached
Construction typeOther
Other construction typeDiffutherm clad I-beam and OSB
Party wall constructionEarth block and timber studwork with plasterboard
Floor area 99.52
Floor area calculation method Treated Floor Area (PHPP)
Building certification  Passivhaus certified building Passivhaus certified building

Project Team

OrganisationMark Tiramani, Shirley Bose
Project lead personMark Tiramani, Shirley Bose
Landlord or ClientMark Tiramani, Shirley Bose
ArchitectJPW Construction
Mechanical & electrical consultant JPW Construction, Mark Tiramani
Energy consultant
Structural engineer
Quantity surveyor

Design strategies

Planned occupancy2 adults working from home.
Space heating strategyNo fixed heating system. Portable oil-filled 0.9-2kW electric radiator. Portable bioethanol burners: 1kW and 2.5kW.
Water heating strategy60% via solar thermal with 220 litre twin coil insulated HW tank. 40% via 3kW electrical immersion heater.
Fuel strategyLPG gas for most cooking. Electric oven. Biothenal top-up heat.
Renewable energy strategy2.5kW ground mounted PV array. 2.5kW wind turbine planned but not implemented.
Passive Solar strategySouth facing main glazing. Window proportions optimised using PHPP, but with emphasis on full height south east corner glazing. 40t internal thermal mass on the ground floor counters overheating potential and winter night-time heat loss.
Space cooling strategy
Daylighting strategyLarge south and east glazing areas combined with a very open plan layout reduces artificial lighting to a minimum.
Ventilation strategyCentral mechanical ventilation with heat recovery. Openable windows for manual ventilation during roughly 40% of the year (MVHR off).
Airtightness strategy
Strategy for minimising thermal bridges
Modelling strategy
Insulation strategy
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 -