An energy rating certificate will always display the holders’ company name and the name of the window at the head of the certificate. Our window names are Efficiency for our C rated; Efficiency Extra for our B rated and for our A rated Efficiency Plus.

The energy index number can be a positive or a negative number. This indicates how much energy the window will save or lose. A positive value means the window will enable more energy to pass through the glass into the room than is going to be lost.

Thermal Transmittance (U value) measures how well a product prevents heat escaping. The lower the number the better the U value is.

Solar Factor measures how well a product blocks heat caused by sunlight.

Effective Air Leakage relates to the volume or air leakage from a window.

Energy ratings are not calculated just on the glass, the window frame is also part of the calculation.

In simple terms, A is the best at conserving energy and the higher the index number is the better. So our +8 A rated windows are amongst the best energy saving windows on the market.