The latest radical eco-houses - and why they'll need no heating at all

They generate their own power, will be exempt from stamp duty - and look amazing, too. Adharanand Finn sees Britain's first zero-carbon houses take shape

"This is the future, today," says Peter Bonfield, the chief executive of Building Research Establishment (BRE), a group of big-thinkers who aim to show the construction industry where the future lies.

He stands marvelling at what looks like, well, a building site. If you walked past it, you wouldn't look twice at the six small plots containing six buildings in various stages of completion just off the M1 near Watford, Hertfordshire. However, by 11 June, the rubble and hard hats will be gone, and the Offsite2007 Innovation Park - BRE's showcase of sustainable building - will be finished.

The name, Offsite2007, comes from the fact that all the buildings are essentially kit houses. They are prefabricated and then erected on site, just like like putting together large items of Ikea furniture. And, in fact, Ikea makes kit houses itself. But when I ask Jaya Skandamoorthy, BRE's director of enterprise and innovation, about the similarities between those and the houses here, he gives me a wry smile.

"The first two Offsites, in 2003 and 2005, were about showcasing prefabricated houses. This year, it has moved on and it is now about pushing the boundaries of sustainability."

The driving force within the building industry towards reducing the environmental impact of new homes has been the Government's Code for Sustainable Homes, launched last December. At the time it was accused by some of being unrealistic.

The Secretary of State for Communities and Local Government, Ruth Kelly, promised that all new homes would be zero-carbon within a decade, and proposals were released for binding regulations that would mean all new homes would have to be 25 per cent more energy efficient by 2010, 44 per cent by 2013, and 100 per cent more efficient, or zero-carbon, by 2016.

While some, including the House Builders Association, criticised this demanding schedule and called it unworkable, others in the industry have been getting on with it, and the results of their efforts will form the main body of Offbuild2007. Six firms will erect full-size buildings that will open to the public and people from the building industry during the event in June.

The star performer, in terms of energy efficiency, looks likely to be a house by building company Kingspan Off-Site, which is aiming to be 100 per cent carbon free - which means all its energy needs will be met by the house itself.

If it achieves it, it will be the first commercially built house in the UK to achieve a top Level 6 score on the Government's new rating system for the sustainability performance of new homes (it's a bit like the A to G ratings you get on washing machines).

The key element to achieving this, and to the efficiency of all the buildings on the site, is insulation. Now, we all know that we should insulate our homes, but we're talking about more than laying rolls of fibreglass in your loft here.

The only house on the site completed so far, by the company Osborne, achieves a sustainability rating of Level 3. However, even this house is so well insulated that it doesn't require any heating, cutting a huge chunk off its energy consumption needs. Part of the reason these houses are so well insulated is the fact that they are prefabricated.

This means they can be built in a more controlled environment where the various tolerances of the materials can be measured more precisely, and parts can be fitted together more exactly. The result is a virtually airtight building.

Lack of any healthy draughts blowing through the rooms means that ventilation becomes important, and each of these houses has its own solution in place.

The Osborne house uses a mechanical heat recovery system - a large box in the attic that sucks moist, stale air out of the rooms through discreet vents, passes it over cool, fresh air from outside in order to maintain most of the heat, and then pumps the clean, warm air, back into the house.

The resulting drop in humidity has the happy by-product of reducing dust-mites, which are one of the main triggers of asthma. "There's no need to ever open a window - it's never stuffy," says Jaya. It all sounds rather clinical, but don't worry, the windows do still open, in case you want to let the outside in.

The fact that these buildings are prefabricated reduces waste, as any off-cuts can be reused and recycled more easily in a factory setting. The precision of factory building means manufacturers can order parts to exact sizes more easily, again reducing waste.

So, will we be seeing these buildings everywhere in the next few years? Well, probably. Despite the advanced technologies employed, these are not niche designs, and the firms building them are aiming at the mass market. Kingspan Off-Site, for example, already has contingency plans in place to build up to 30,000 homes in the next few years.

Initially at least, the higher sustainability ratings will mean the houses cost more, although owners will have lower fuel bills. The Osborne house, for example, will cost approximately 2 to 5 per cent more than an identically specified traditional new build, but it will have total energy bills of around £100 a year. In addition, any new homes achieving a Level 6 rating will be exempt from stamp duty.

So the Government's ambitious sustainability targets for 2016 could be met through the miracle of off-site building. It seems the future is airtight for us all.

www.offsite2007.com

We have the technology

* Builder Stewart Milne will be showcasing a house that can be both warmed and cooled by a new substance that has been developed by the company DuPont, called Energain. Installed on the interior walls and ceilings of the building, coated panels absorb and release heat depending on the temperature, reducing the need for energy-hungry air conditioning or heating.

* The Stewart Milne house also features a recycling system for "grey" water from EcoPlay UK, which collects and cleans bath and shower water so it can be reused for flushing the toilet. It will empty the saved bath water if it begins to smell.

* All the houses on the site come fitted with "smart" wireless technology, which has many environmental benefits. As well as letting you turn lights off and pull curtains remotely, say while you're still working in the office, the technology can be used to measure energy and water use. According to the Building Research Establishment, this provides "the means for end-users to significantly reduce consumption and avoid waste".

* The house built by the company Spaceover uses a complex system of pumps, compressors and pipes dug into the ground to extract the natural heat from the earth under the house to heat the rooms and the water. The system requires energy to drive the pumps, but uses 40 per cent less energy than a conventional heating and hot-water system.