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Dundon Passivhaus

Location: Compton Dundon, Somerset
Completion Status: December 2013 Occupancy: Occupied
Architect: Prewett Bizley Architects Consultant: Prewett Bizley Architects, Structural Engineer: Structural Solutions, MVHR: Green Building Store, PH Certifier: Warm
Contractor: Main self-build: Graham Bizley, Ground work: GA Doble; Timber Frame: Allwood; Windows & Doors: SIGG supplied by JPW construction, Roof: ARM Roofing, Warmcel installed by Tinhay Client: Graham Bizley
Certification: June 2015 Certifier: WARM
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Small Projects Finalist: UK Passivhaus Awards 2015. A detached low-energy home built to Passivhaus Standard, nestled at the foot of a wooded hill on the edge of a Somerset Village.

Dundon Passivhaus is an extremely energy efficient house overlooking the expansive landscape of the Somerset levels.  Built as a self-build project with the owners as the clients, designers and main contractors, the house replaced a dilapidated 1920’s bungalow.  By digging the lower floor into the hillside planning permission was gained for a two-storey house with a roof that is only marginally higher than the bungalow it replaced.  The house is intended to sit unobtrusively in the landscape, emerging from the hillside but rooted in its context.

The design developed around an interest in how to build in harmony with a rural setting and the desire to use as little energy as possible.  Architecture doesn’t have to be sacrificed to achieve excellent energy performance. 

The thermal envelope is defined by thick, timber-framed walls clad with green oak boards.  On three sides the shallow pitched roof extends beyond the footprint to create sheltered outdoor spaces that catch the sun at different times of day.  An out-rigger structure of green oak posts supports the roof and frames views through the covered spaces, binding the building into the landscape.  The roof overhangs work in harmony with the energy strategy by providing summer shading to the large areas of glazing.  The weathered oak has a similar tone and colour to the local blue lias stone used on houses in the area, while the roof pitch and structural proportions are similar to near-by agricultural buildings. 


The internal spaces connect with particular external spaces or features in the landscape via large windows, making each room distinct and drawing the surrounding countryside in.  The two floors have particular architectural characters.  The upper floor entrance hall and reception rooms are lined in planed oak with oak joinery, a more refined version of the rough sawn external cladding.  Elsewhere the walls are lined with plywood and painted in warm shades of grey to create a more serene atmosphere. 


We chose to build a Passivhaus because the PHPP offers a clear and comparable standard of calculation founded on principles of building physics, and as such is the most useful tool we have found to design genuinely low-energy buildings.  In the first year of use the Primary Energy Demand has been about 85 kWh/m2. The house has a solar thermal array and a wood-burning boiler stove to heat water in the warmer months.  The wall construction is vapour permeable to moderate humidity, working in conjunction with an MVHR system to create a healthy internal atmosphere.  An electric heater in the ductwork will provide space heating on very cold days. 



Green oak columns support the roof, tied back to the main timber-framed structure which is clad in green oak. The wall construction is vapour permeable to moderate humidity and create a healthy internal atmosphere.


Further Information

Dundon Passivhaus poster


Prewett Bizley Architects

UK Passivhaus Awards 2015 Presentation

Winner of RIBA National Award 2015







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