Energy efficiency: low-energy housing Future homes will have to comply with the government's energy-saving plans. Two South-east schemes are proposed models: which is better?
For the first time since the 1960s, consultants are experimenting with housing design on a large scale. The government predicts that 4.4 million new homes will be needed by 2016 and is demanding that these dwellings are far more energy-efficient than is commonplace today. Solar energy, combined heat and power, and water recycling are just some of the features being incorporated into housing schemes for the next millennium.

Two high-profile schemes are being proposed as models for low-energy housing. One is the much-publicised Millennium Village in Greenwich, south-east London. This is a commercial scheme of flats that will use 60% of the energy of conventional housing. The other model is the proposed Beddington Zero Energy Development in Sutton, south London. This scheme will produce town houses that consume only 10% of the heating energy of a conventional home of equivalent size.

But the Millennium Village has come under heavy fire even before a brick has been laid. Critics say the scheme's sustainability and innovation targets will not be met until the final stages of the development. So, most homes will not meet the proposed targets 鈥� indeed, early units are aiming for an energy reduction of only 25%.

The developers argue that because the scheme is commercial, they cannot incorporate innovations that will inhibit sales of the units. For example, the developers can only recommend energy-efficient white goods to buyers, not sell them as part of the homes.

The Millennium Village consortium, comprising Countryside Properties, Taylor Woodrow, Moat Housing Group and Ujima Housing Association, lead architect Ralph Erskine, project architect Hunt Thompson, service engineer Battle McCarthy and project manager Trench Farrow, is unconcerned by the criticism. "To meet its energy targets, innovation on the development will be phased," says Richard Hodkinson, director of engineering and innovation on the project. This means that only dwellings built near the end of the project will aim for the 80% energy reduction target.

The Beddington scheme, which was submitted for outline planning permission last month, has potential for far greater energy efficiency than the Millennium Village. Designers have been more daring because a high proportion of its accommodation is for rent or part-ownership. Whereas the designers of the Millennium Village want a local combined heat and power plant but cannot afford one unless it is privately financed, the Beddington team is committed to financing a combined heat-and-power plant as a central plank of its proposal.

Beddington Zero Energy Development, Sutton What is it?

Beddington Zero Energy Development is a scheme of 90 dwellings that are designed to use 90% less heating energy than conventional houses. Built on a former industrial waste dump, the majority of dwellings are for rent or part-ownership, although some will be sold to private buyers.

The development will comprise a mixture of grass-roofed town houses, maisonettes and flats, as well as independent workshops. It is hoped that residents will work from home or use the workspaces to reduce the energy consumed travelling to and from work.

The design team 鈥� architect Bill Dunster and Ove Arup environmental engineer Chris Twinn 鈥� has plumped for a radical design that will not include conventional heating equipment. Some of the money that would have paid for a central heating system has been used instead to improve insulation. It is proposed that heating will be provided predominantly by waste heat from cooking and from solar heat gain.

Increasing air-tightness and insulation usually means an increase in condensation, so the designers are developing a special passive heat recovery ventilation unit to draw moisture out of the building. They claim the energy-saving measures should slash energy bills to less than 拢250 a year, compared with the conventional 拢750.

Millennium Village, Greenwich What is it?

Proposed in February 1998, the Greenwich Millennium Village is intended as a showcase for energy-efficient housing. The 32-acre development, a stone's throw from the Millennium Dome on London's Greenwich peninsula, aims to use 80% less energy than conventional housing 鈥� half by reducing energy use in the home, and half by improving the efficiency of energy supply.

The 拢250m scheme is a commercial development of 1400 homes. Comprising a mixture of mid-rise apartment blocks and more traditional housing, most of the homes will be sold to the public, and just over 100 rented out. Laid out in a rough horseshoe, cupped towards the river, the site's tallest buildings 鈥� housing the most prestigious apartments 鈥� will occupy the prominent river frontage and will be the first of four phases of construction. A show home is to be built in time for the new millennium.

In the first phase, the design team aims to reduce energy consumption to a quarter of that for typical dwellings. This will be achieved mainly by increasing the insulation of walls and windows.

The development also has "innovation targets". Legal agreements with Greenwich council have been drawn up to improve construction through innovation. But critics point out that the agreement states that any innovation incurring a "cost penalty" does not have to be included.

How energy will be conserved at Beddington Increasing insulation Insulation levels will be increased to levels where no conventional space heating is required. Using exposed concrete as a thermal regulator Concrete cools the homes during the day by absorbing heat. It then releases it back into the building鈥檚 spaces at night when temperatures fall. Using sunlight for heating and lighting To maximise free heat and light from the sun, the buildings鈥� highly glazed frontages will face south. In the future, photovoltaic panels will be used to shade the integral conservatories and to provide electricity. Enabling occupiers to see energy being used Energy meters will be installed in kitchens to show how much power is being consumed at any time. The developer hopes this will educate users to be more aware of energy use. A scheme to bulk-buy energy-efficient appliances is being investigated. Using a combined heat and power plant A centralised combined heat and power plant will provide enough energy for the whole development. The plant will be fuelled by tree waste, until a fast-growing willow coppice fuel system is in place. Using recycled water instead of mains water Water from the toilets will become a resource, used to water the willow coppice. Rain for irrigating the grass roofs will be collected in the site鈥檚 ditches and ponds, and in large storage tanks for flushing toilets. How energy will be conserved at Greenwich Increasing insulation Just over 25% of the final energy targets will be met by upgrading insulation in the walls and windows. Reducing energy loss through air leaks The cladding will be factory-produced and supplied to site with windows pre-fitted, for a better match between window and wall, so fewer draughts. Using more heat from the sun To take advantage of passive solar heat gain, flats will have a large glazed area on the south elevation. Making users aware of energy use Energy meters in the dwellings will allow occupants to monitor energy use. Booklets encouraging the use of low-energy appliances will be distributed. Using a combined heat-and-power plant This is usually a tractor engine generating electricity and reclaiming waste heat. Because the engine is located close to the homes, power losses from transmission are low. It is likely that the developer will use a design-build-finance-operate solution in the later phases of the scheme, and conventional boilers in the early phases. Specification of low-energy materials Specifiers are using the 精东影视 Research Establishment鈥檚 Green Guide to Specification to choose low-energy construction materials. Careful water management By using bath water for flushing and installing dual-flush toilets, mains water demand may fall 30%.