Set at the foot of a wooded hill, the Dundon Passivhaus is an extremely energy-efficient house overlooking the Somerset Levels
Built as a self-build project with the owners as the clients, designers and main contractors, the house replaced a dilapidated 1920s bungalow. By digging the lower floor into the hillside, planning permission was gained for a two-storey house with a roof only marginally higher than the bungalow it replaced. The house is intended to sit unobtrusively in the landscape, emerging from the hillside and nestling into its context.
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 outrigger structure of green oak posts supports the roof and frames views through the covered spaces, binding the building into the landscape.
Different rooms relate to 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 distinct 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.
The house is being certified to Passivhaus standard, which means it achieves very high levels of insulation and air-tightness. The wall construction is vapour-permeable to moderate humidity and creates a healthy internal atmosphere. Mechanical ventilation with heat recovery provides constant fresh air throughout the colder months when it is undesirable to open the windows. The roof overhangs work in harmony with the energy strategy by providing summer shading to the large areas of glazing.
- Graham Bizley, director, Prewett Bizley Architects
Gross external area 286m2
Build cost £485,000
Cost per m2 £1,695
Contract type Self-build
Work started January 2012
Occupation November 2012
Completed December 2014
Dwelling CO2 emission rate 3.3kg/m2/year