Document L Explained:

  Document L came into force April 1st 2002, it is the building regulations compliance requirement. We answer here some of the most common questions that have been asked regarding Document L. If you have further questions please contact The World of Windows.

What is Document L?

Document L is the part of the Building Regulations for England and Wales that sets the standards of energy effeciency in buildings. The equivalent section of the Scottish Building Regulations is known as Part J. Please note that there are some variations between the two documents.

The new Document L now comprises two separate sections L1 refers to dwellings and L2 refers to non-dwellings.

Why are the changes being introduced?

As part of the Kyoto agreement, the UK Government has made commitments to reduce emmissions of greenhouse gases, such as carbon dioxide, which are harmful to the environment.

What has this got to do with energy efficient buildings?

Generation of the energy we use to heat, light and cool our buildings accounts for almost half of the carbon dioxide emissions in the UK.

Energy efficient buildings help to reduce pollution that damages the ozone layer and conserve dwindling natural fuels for future generations.

What are the changes to Document L?

The changes require the use of more energy effecient building products (for example, those used in walls, windows, floors and roofs) and building services (such as lighting, heating and ventilation). At the same time, the new document extends the scope of work covered by building legislation.

Do the changes apply to all buildings?

The previous version of Document L covered construction of new dwellings (houses) and non-domestic buildings, such as offices and public buildings. The new Document L still covers these but goes further by addressing work on existing buildings, such as replacement windows installed as home improvement.

What will be the impact on the glass and window industry?

With this new document, the installation of double-glazed units manufactured with standard glass will no longer be acceptable in most situations.

In the case of replacements, all windows have to be double-glazed with a low-E glass, and meet a certain standard of thermal performance or U-value. By windows, we mean the frame and the double-glazed unit combined.

For new build, both dwellings and non-domestic buildings, windows, doors and rooflights also have to meet certain U-value, although compliance is more complicated and further advise should be sought.

What is U-value?

The U-value measures the rate at which heat is lost through a material. The lower the U-value, the lower the amount of heat lost and the lower the amount of energy wasted. U-values are measured in Watts per square metre per degree of temperature difference (abbreviated as W/m²k).

Are there any exceptions?

Listed properties and buildings in conservation areas may be exempt as are display windows and shop entrance doors.

Also replacement doors which have a glazed area of less than 50% are not required to meet the new U-values.

Does Document L apply to conservatories?

As long as a conservatory is unheated and separated from a house, it does not have to comply with Document L.

Why should I bother to comply?

Complying with Building Regulations is a legal requirement.

How can I find out more?

Please contact The World of Windows should you require more information on this subject.