By Jill Macnair
The Sunday Times
20 January 2008
Home gave three leading eco-architects different budgets and one brief: to create a sustainable urban family dwelling. Our correspondent is impressed by the results.
exert…
Justin Bere, principal of the north London-based firm Bere Architects, designed a four-bedroom, 1,800 sq ft home costing £400,000 (plus land costs). His residential projects include Focus House, built in 2006 in Finsbury Park, north London, which won the Riba London Region Award 2007, among other prizes. His practice is a devotee of PassivHaus, an established German style of energy-efficient construction.
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The PassivHaus
£400,000
Justin Bere’s four-bedroom, £400,000 PassivHaus doesn’t need a boiler, radiator, underfloor heating or air conditioning. Instead, it stays warm in winter and cool in summer by limiting its energy consumption. The basic structure is made of laminated wood panels from sustainably managed forests. The wood has absorbed CO2 – up to 35 tons – that would otherwise pollute the atmosphere.
The home has a skin of oriented strand-boardpanels – like chipboard, but less chemically based – making it 14 times more airtight than required by British building regulations. Zinc cladding creates a durable, waterproof finish – and looks stylish.
The heavy insulation also exceeds building regulations. All windows are triple glazed, and the south-facing facade has large glass sections that let in daylight and keep the need for artificial light to a minimum. They are also carefully planned to provide cross-ventilation in summer, when opened.
Smaller windows on the north side minimise heat loss, and external timber louvres reduce overheating. By opening and shutting them, you can control the amount of light – and heat – entering the house.
If the building is airtight, how does the air inside stay fresh, in winter in particular? Thanks to a whole-house ventilation unit with heat recovery. This transfers heat from the stale air leaving the building to the fresh air coming in. “When a building is airtight, it’s essential to incorporate a system for bringing ample fresh air into the house, to make sure it’s healthy,” Bere says.
A small ground-source heat pump boosts the temperature if necessary (such as when the house is left unoccupied during holidays: some of the heat the house uses is provided by the body heat of the occupants).
Domestic appliances are all A-rated, lights are low voltage and energy efficient, and a 3,000-litre rainwater-harvesting tank beneath the garden provides water for the sprinkler system (which meets fire regulations), the six-litre dual-flush lavatories, the washing machine and an external tap for the garden. The tank reduces pressure on the public sewer during periods of high rainfall, playing its own small part in reducing the risk of flooding.
Glass-tube solar panelling fitted to the roof provides at least 65% of the home’s hot-water requirements, and the heat pump can boost domestic hot water if necessary.
Finally, roof gardens help to moderate the microclimate and encourage biodiversity.