Conservation of Fuel and Power

In Scotland, the requirements for the conservation of fuel and power are covered by Part J of the Building Standards. The current Regulations were introduced in March 2002, but only came fully into effect in March 2003, when “Class Relaxation 140” expired. The Regulations following the expiry of the Class Relaxation are summarised in Bulletin 5: Building Standards (Scotland) Regulations Part J .

In brief, U values of either 2.0 or 2.2 w/m² K are needed for metal windows (depending on the circumstances) and 1.8 or 2.0 for non-metal windows. This means low emissivity glass is necessary.
A more detailed technical summary, and guidance on how to comply, is given in Glass and Building Regulations: Thermal Insulation and Energy Efficiency .

The regulations have recently been reviewed and a new Technical Handbook (Section 6 - Energy) has been published. This will come into effect in May 2007. For windows, probably the most significant development is that Window Energy Ratings (WERs) are introduced as a criterion for compliance for domestic replacement windows. A WER band D will comply. You can find out more about WERs in our Window Energy Ratings Bulletin 3.