Max Fordham House

As well as providing beautiful daylight, windows allow solar radiation to warm a house during the day. At night, a window typically loses ten times as much heat as a wall. On freezing overcast days, more heat is lost through a window at night than gained during the day. We have altered the behaviour of the windows so that they are net contributors to the building’s heat balance, even on a freezing, overcast day. Automated, insulated shutters allow the windows to become much more insulating at night so that the windows are thermally a net benefit every day. The windows and their positions are designed so that electrical lights are not needed during the day.

As the house is designed to not need any heating on the coldest day, it needs to be capable of getting rid of heat every other day. The thermally massive structure and windows that open widely help with this. The windows can also be slightly open with the shutters closed, and the shutters are glossy and reflective on their outer face.

Domestic hot water is the house’s largest energy demand. Solar thermal technology was considered, but introduces the complication of an additional mechanical system and requires valuable roof space - the roof area is already maximised for photovoltaic electricity generation. A rooftop copse of hazel plants on the first floor level contributes to biodiversity.

Heatpump technology aligns well with the continuing decarbonisation of the national electricity grid. A two-stage heatpump provides the high grade heat needed for domestic hot water quite efficiently year round. While some summertime efficiency may be sacrificed in the second compressor, this is compensated by the high wintertime efficiency and the lack of immersion heating needed. The heatpump’s air-side heat exchanger is located within a suntrap and is controlled so that 24 hours worth of domestic hot water demand is produced during mid-afternoon, when air temperature is warmest and the heatpump most efficient. This is also when the roof PV array is likely to be at its most productive.