The BFRC is a wholly owned subsidiary of the glazing industry’s trade association, the Glass and Glazing Federation. Its ratings scheme for Energy Efficient Windows is a voluntary scheme that uses energy labels specifically produced for windows that are similar to the energy labels seen on most household appliances. It sets extremely stringent standards for windows to be rated. The most energy efficient windows are rated from A to C.
BFRC Window Energy Ratings/ “U” values
There are currently two main methods used for the assessment of insulation in windows and doors. The first of these is “U” values which in its simplest terms applies a measured heat source to one side of a product and compares measurement of heat on the opposite side. The difference between internal and external measurements provides us with an indication of the insulation properties of the material which is expressed as a “U” value. The lower the “U” value, the better the insulation of the property.
Nowadays the familiar Energy Rating label may be found on electrical goods, cars and of course windows. The label allows us to identify products which are independently assessed in relation to their energy saving features and allows us to make an informed choice regarding the products which best suit our requirements. Window Energy Ratings are more complex as they use three values to calculate the performance of a window which are all clearly displayed on the Window Energy Ratings label. The first of these is the “U” value mentioned above this takes into account the “U” value of the whole window (PVC-u frame and glass combined). The second measurement is the Solar Gain or “G” value which looks closely at the contribution which may be made by natural sunlight streaming into your home. For example, you may have a glass product which has excellent insulation properties but if the specialist glass coatings reduce the light transmission then the natural light streaming through your windows contributing heat to your home will be reduced. This can often be an issue with triple glazed products which often have a high “U” value but a lower Solar Gain “G” value as each pane of glass reduces the amount of naturally captured light/heat we can harvest from the sun. The third measurement used in a Window Energy Rating is Effective Leakage or “L” Value and this would take into account the air leakage in a window. Put simply the higher the “L” value, the more air that escapes through the window.
The three test measurements, “U” value, “G” value and “L” values are built in to a formula, which then produces a numerical score for each individual window. The ratings for windows are ranked from W.E.R. “A” Rated to W.E.R. “G” Rated. For a product to be W.E.R. “A” Rated the product must have a numerical score of 0 (zero) or above whereas a “G” rated product may have a numerical score of -71 (minus seventy-one). For example, our “A” Rated casement range has a fabulous score of +7 (plus seven). We would highlight that whilst “U” values have a place in product assessment, the testing carried out for a Window Energy Rating is much more comprehensive and examines the quality and performance of glass, window frame material and air infiltration which in turn produces a more rounded result.
Please be aware that you should always insist that you validate company claims by asking to see their W.E.R label which should contain the company name.
> BFRC website