Self Certification for Glazing


As part of the Kyoto agreement, the UK Government has made commitments to reduce emissions of greenhouse gases, such as carbon dioxide, which are harmful to the environment. Generating 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 windows will help to contain and conserve heat within the home, keeping out wind and rain, resisting condensation and yet allowing natural “free” energy - the warmth of the sun - to heat the home. They can be made using any frame material including aluminium, PVC-U, steel or timber.

The rating formula used to calculate energy efficient windows was determined by following the methodology adopted by the European Window Energy Rating Scheme, EWERS, which was developed as part of the EU ‘Save’ initiative.

A window's rating is determined by a mathematical formula. The values used in the rating formula are based on the energy balance of a notional house through an average UK year, with notional window sizes and configurations. The performance of a real window, in a real building, will differ from that of the notional window used for the rating calculation. In some cases the performance will be better and in others it will be worse. The purpose of a Window Energy Rating is to allow one window’s energy performance to be directly compared to another under standard conditions. All new and replacement windows either have to be rated C or better or have a U-value of 1.6 or lower. Click here for more information on the calculation.

The energy performance of the window, when installed, is heavily influenced by the quality of the installation. Therefore, the Thermal Rating Register recommends that all windows are fitted by Competent Person Scheme members, such as Certass, only.

Contractor Home

Glazing Industry

If you work in the Window Industry, see this section
Click here to join TRR today
Homeowner Home


If you are a member of the general public, see this section

CE Mark

Click here to find out about CE Marking CE Mark