NEG Window Energy Ratings (WER's)
Window Energy Ratings (WER's) were launched in March 2004 by the British Fenestration Rating Council (BFRC), an independent government supported body established to develop and administer a system of Window Energy Ratings in the UK.The idea was to develop a consumer friendly method of illustrating which windows performed well in terms of energy efficiency using the same type of labels already seen on white goods.
A window's energy rating is determined by a formula which takes into account available solar heat gains (window g-value) and subtracts the thermal losses (window U-value and air leakage).
* WER = Solar Gains - (Thermal losses and air leakage)
The resulting value (energy index) is then placed into a band on an A-G scale consistent with other energy performance labels.
A BFRC rating and label apply to a whole window (i.e frame and glass). They do not apply to either the frame, or the system or the glass individually. Therefore it is at the point where all these components come together to produce a whole window that the rating and label are obtained.
The A-G rating system provides a means of promoting energy efficient windows to the consumer. Already, windows
with a C rating or higher are endorsed by the Energy Saving Trust's 'Energy Efficiency Recommended' scheme and may carry the EER logo. The EST has also prodcued a series of Best Practice Guides for windows in new dwellings which use the BFRC ratings and the measure of a window performance. Good practice is achieved with D rated window and Best Practice with C Rated.
Improved Energy Ratings
The overall performance of a window is determined on the combined effect of the frame and glazing components and the air tightness of the finished window. Ratings may be improved by decreasing thermal losses and/or by increasing solar gains. NEG can help achieve these by providing the following:
Decreasing Thermal Losses
Type of low-E glass: with its optimised balance of very low emissivity and high solar gain SGG Planitherm Total can improve the energy index for a given window by about 5kWh/m2/year* when compared to hard coated low E products.
Inert Gas Filling: argon gas filling can improve the energy index for a given window by about 11kWh/m2/year* compared to an air filled unit.
Warm Edge Spacer: using a warm edge spacer can improve the energy index for a given window by about 7kWh/m2/year* compared to standard aluminium spacer.
Optimised Cavity Width: the optimum cavity width for an argon filled unit is 15mm (10mm with krypton)
Increasing Solar Gain
Low - Iron Glass: replacing the outer pane with a low iron glass such as SGG Diamant can improve the energy index for a given window by about 6kWh/m2/year*.
For A-D ratings, the difference between each band is only 10kWh/m2/year*. So it is clear that simple changes can make it possible to achieve much better ratings.
How to obtain a Window Energy Rating Label?
We are reguarly being asked by customers, how as window manufacturers or installers, do we obtain a BFRC Window Energy Rating Label? As this has proved to be an area of such confusion and miss-information, we have compiled these guidance notes about this process.
The insulating glass unit (IGU) is the major component that affects the performance of any window, and we at NEG are in a position to supply IGU's that:
* Conform to EN1279 Parts 2 & 3 an essential and mandatory requirement.
* Can include a variety of energy efficient and low iron glasses.
* Can include Toughened Safety Glass to EN12150 Class 1
* Can include a variety of warm edge technology technology spacer bars of different cavity widths
* Can include a number of options of gas types
We can also assist in providing further advice through our preferred consultants, CEN solutions Ltd.
If you are a manufacturer, you may need to apply for BFRC approval using the following route:
- Implement a factory prodution control system (FPC) that provides traceability
- Obtain a BFRC simulation from an approved BFRC WER simulator.
- Have the FPC and simulation audited by a BFRC Independent Agency.
- If your FPC is approved, the IA will then recommend BFRC to accept the registration.
- When registered you will be able to label your windows.
- Once a year your system will require auditing by your preferred IA to maintain your compliance.
Installers may be able to have a BFRC label in their own right or as a sub label. If you are an installer, you have to comply with most of the points above but the procedure in respect to the FPC is simplified. Also simulations may be obtained, by less onerous ad expensive routes from your frame suppliers.
Although BFRC rules have varied over the past year, the above summarised routes to conformity are based upon current information. At Northern Express Glass Limited we have an excellent relationship with a well established firm of consultants to the fenestration industry - CEN Solutions Ltd. We would suggest that for further free advice you contact one of their consultants via their website www.censolutions.com.
