Smart homes run on solar power and body warmth

Imagine a four-bedroom home that makes its own electricity, provides its own water and sewerage services and doesn't even need radiators. Body heat and light from the sun are more than enough to provide free year-round central heating.

The BA Festival of Science yesterday heard the latest news from the Hockerton Housing Project, a terrace of homes built five years ago in Hockerton just north of Nottingham in Central England. The homes take self sufficiency to the extreme, with their owners already planning to start selling electricity back into the UK grid.

Mr Simon Tilley, his wife and three children have lived at Hockerton for the past five years. "The interesting thing about this house is it is very comfortable to live in," he said. It has all the amenities including television, fridge and cooker, stays at about 18 degrees Celsius all year, including winter, without heating, and saves the Tilley's about €1,500 a year in utility charges. "We have tried to do it without loss of amenities." The experimental homes were built for the same money as conventional houses but are anything but conventional. The ability to avoid having to heat them comes down to a single issue, insulation, he said.

"It is actually quite simple - lots of insulation - but with the connection it is a high mass construction," he explained. "It is like a night storage radiator." Many old churches stay warm in winter and cool in summer because of their heavy stone walls.

The Hockerton homes use thick reinforced concrete and block walls, and then use an extra trick by putting the insulation not inside but outside the walls. "That is the only trick. Just by doing that, you make the mass work for the year."

There are of course a few more innovations. The fronts of these wide homes are all triple-glazed glass to collect as much free solar energy as possible. There is also a double glazed porch to help isolate the front door.

There are no windows or doors to the rear as these are banked up fully with earth, and right up across the roof which is grassed over. The terrace is only visible from the front. From the back, it looks like a low hill.

His electricity bill last winter was just €43 and he only uses about eight kilowatts of power a day, he added. His parents have a smaller home and live alone but they still burn up 80 kilowatts a day. No energy is wasted. "Part of the input to the home is body heat," he said.

Fans draw heat through ventilators to reduce humidity and fresh air is warmed with heat exchangers so nothing is lost.

Rainwater is collected and purified and sewerage is treated on site. There is a link to the power grid for now, but a windmill is planned and extra power will be sold on.