The British Woodworking Federation (BWF) has published a new edition of its comprehensive guide to the improved U values that must now be achieved by timber windows and external doors.

An average whole window U value of 2.0W/m2K or less now needs to be achieved following Approved Document L 2001, which came into effect on April 1.

In addition to new U values, the guide says air space for double glazing is likely to rise to a minimum of 12mm to achieve an acceptable value and all glazing is likely to need a Low E coating.

The implications of the standards, methods of achieving them, the issue of certification and possible exemptions are also covered.

For more information contact the BWF on 020 7608 5050.