Tougher UK Building Regulations for April 2006

Higher standards of insulation and control of air leakage in buildings is called for in the forthcoming revised UK Building Regulations. In particular, Part L of the Building Regulations has been reviewed with a brief to make new buildings more energy efficient and to tackle climate change. The revised changes will be enforced from April 2006.

This will mean new buildings will need to be better insulated and use more efficient heating systems. And importantly, for the first time the revised Part L1 (for dwellings) will make air pressure leakage testing mandatory. Poor levels of air tightness in buildings can contribute significantly to heat loss since warm air will be replaced by cold air due to thermal air currents, or in simple terms drafts!

1. L1A – New Dwellings

A key requirement for new dwellings is a minimum energy performance standard. This is being expressed in terms of a Target carbon dioxide Emission Rate (TER). Calculating a Dwelling carbon dioxide Emission Rate (DER) for the actual dwelling and ensuring that this is no greater than the TER will be part of the overall requirement to demonstrate building regulations compliance.

Another important requirement will be for the performance of the building fabric and the fixed building services to be no worse than specific design limits set out in the approved document. The aim is to reduce heating demand by limiting heat loss through the fabric of the dwelling. It will also place limits on design flexibility to discourage excessive and inappropriate trade-off. For example, dwellings with poor insulation levels made to comply by using renewable energy systems such as solar or wind energy.

The full set of criterion which will need to be demonstrated in order to comply can be seen in the interim version of AD L1A.

2. L1B – Existing Dwellings

The changes to the building regulations AD L1B recognise the importance of the existing housing stock, and have extended the range of energy efficiency improvements which should be carried out at the appropriate opportunity. Requirements now cover aspects such as worst acceptable U-values for walls.

New Insulation Solutions Will Be Required

Conventional insulation products such as mineral wool have already reached the maximum practical depth at which they can be installed under existing regulations with 250 to 300 mm depths on loft ceilings being installed to meet current building regulations for U values. Also wall cavities would have to increased again (currently 75 mm is the standard cavity width in new build homes) but with the danger that walls become unstable the further apart the inner and outer leaf of the wall becomes.

Polyurethane foam insulation products have been commercially available for over 30 years to the construction industry but the adoption has been low due to cost disadvantage. The new regulations mean that new methods of construction will have to be sought if conventional insulation is to be continued to be installed and this will add to design and build costs. Polyurethane foam offers the advantage that it will achieve the new U values required within current house designs, will be quicker to install and the absolute cost continues to fall as new methods of manufacturing polyurethane foam lower costs and increase the supply.

Rooftherm have looked at the new regulations, particularly the revised section Part L that now calls for even lower U values to be achieved in new dwellings and building conversions. To help specifiers and builders meet the new and revised sections of the Building Regulations Rooftherm are offering a free consultancy on how spray foam polyurethane can help meet or exceed the Regulations.

Spray foam polyurethane is a superior insulator and needs less depth of material than any other commercially available insulation product for any given U value. One aspect that the new Regulations will make difficult is building design where sufficient space for the insulation material to be installed will have to be allowed for and increased unless polyurethane spray foam is used. Sprayed polyurethane foam also has the benefit that it prevents air leakage as it acts as a sealer.