All buildings will have to be better insulated. The document calls for “a significant increase in the insulating performance standards for building fabric”. So, the walls, floors, roof and windows of all buildings will have to have more insulation installed or be constructed from materials with better insulating properties.
The proposed increases are so high that the DETR has chosen to implement the changes in two phases. The U-values called for in the first phase will be achievable using current products; the second phase will be much more difficult to achieve – the box on page 20 gives the figures proposed.
However, these U-values are not absolute – they can be relaxed if an efficient heating system is installed. The government accepts that meeting these targets will present construction with tough targets. “The changes will be a challenge to both the industry and product manufacturers,” said a DETR spokesman. To ensure that the insulation performs effectively, the changes propose increasing the standards of detail design and site workmanship to reduce the incidence of gaps in insulation.
Having increased the thermal performance standards of the building fabric, the regulations then address the heat loss through unwanted ventilation. The aim is to improve air-tightness by improving the way buildings are constructed. Designers will have to adopt design details that are acknowledged to work or to submit a building to a fan pressure test to measure the air leakage directly. For large buildings, the proposals recommend a mandatory fan leakage.
A fundamental change to the regulations is a change in the definition of building work. By widening the meaning of “material alteration” in the proposals, the government has managed to bring work on existing buildings within them. At the moment, this will extend only to replacement windows and boilers. These will now have to comply with the new regulations rather than those of the unit being replaced.
However, some organisations want the regulations to concentrate on the existing building stock and not on new buildings. A spokesperson for the House Builders’ Federation says the government should concentrate on improving older, energy inefficient homes rather than a minority of new ones.