Passivhaus Pioneer
Seymour-Smith Architects’ Underhill House has already claimed a first; it is the first certified, quality-approved domestic Passivhaus in England. The Passivhaus standard relies on a simple set of principles: very high levels of insulation, elimination of cold bridges, super-insulated triple glazed windows orientated to the south to maximise passive solar gain, and an extremely well sealed building fabric. It also demands mechanical ventilation to provide good air quality and highly efficient heat recovery. This produces a home that retains heat from passive solar gain and activities such as cooking, watching television and showering, and uses that to eliminate the need for central heating. Underhill House reflects these principles faithfully. The L-shaped house has two south facing sides, both glazed throughout with triple glazing to maximise solar gain and natural daylight while minimising heat loss. The remainder of the structure is earth-sheltered and highly insulated. Where possible, the construction uses materials with high recycled content. Concrete contains pulverised fuel ash and ground granulated blast furnace slag as cement replacements, and incorporates recycled aggregate. External paving uses the by-product of the china clay industry, screed is made from crushed glass bottles, and internal blockwork includes recycled sawdust. Most of the home’s electricity will be generated by photovoltaic panels, which also double as solar shading. Mechanical ventilation with heat recovery connects to the hot water store. One side of the roof is covered in an innovative glass slate system with solar hot water collectors beneath, and there is a small back up wood stove. The home is completely boiler-free. Internally, the aesthetic is functional and minimalist. The concrete structure is exposed and the galvanised steel ventilation ductwork and wiring conduits celebrated rather than concealed. There are dropped ceiling panels for acoustics and to define different areas within the large open plan living space. Internal block walls have a thin spray applied plaster finish.
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