Underhill House

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Underhill House, a strikingly-modern earth-sheltered home, was the first house in England to achieve certified Passivhaus status - widely regarded as the worlds leading standard in energy efficient construction.Designed by UK architect Helen Seymour-Smith, Underhill House was developed underneath and adjacent to a derelict 300-year old barn situated in a prominent and beautiful location on a hillside in an Area of Outstanding Natural Beauty (AONB) in the Cotswolds.Sensitive restoration of the existing barn and an innovative design ensured the project has minimal visual and environmental impact. Not only was the external form of Underhill House designed to minimise visual impact on the surrounding landscape, the interior finish and construction materials were carefully chosen to make the building as environmentally sustainable as realistically possible.
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Underhill House : 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

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Renewable energy

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

Calculation and targets

Whole house energy calculation method
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Energy target PassivHaus
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Pre-development air permeability test--
Final air permeability test--

Project description

Start date
Occupation date
Location Moreton-in-Marsh Gloucestershire  England
Build typeNew build
Building sectorPrivate Residential
Property typeDetached
Construction typeConcrete frame
Other construction type
Party wall construction
Floor area 358
Floor area calculation method Treated Floor Area (PHPP)
Building certification  Passivhaus certified building Passivhaus certified building

Project Team

OrganisationSeymour Smith Architects
Project lead personSeymour Smith Architects
Landlord or ClientMr & Mrs Seymour-Smith
ArchitectSeymour Smith Architects
Mechanical & electrical consultant
Energy consultant
Structural engineer
Quantity surveyor

Design strategies

Planned occupancy
Space heating strategy
Water heating strategy
Fuel strategy
Renewable energy strategy
Passive Solar strategy
Space cooling strategy
Daylighting strategy
Ventilation strategy
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

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Opaque doors description
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Windows description
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Rooflights description
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