A Rated Windows
The Government approved Window Energy Ratings scheme rates windows on a scale from G being the lowest up to A+ being the most energy-efficient windows. The current building regulations concerning the energy efficiency of homes require that windows are a minimum of band C however most window companies are aiming to provide the homeowner with the highest energy efficiency achievable at a good price.
How to get an improved Window Energy Rating - Aiming for A-rated windows
The type of low-e glass used in the window glazing is not the only factor affecting the Window Energy Rating of an energy efficient window. Other factors bring about significant changes in the rating and these can be achieved by:
- improve the window g-value (amount of free heat from the sun the window lets in) without compromising the U-value, or
- improve the window U-value (the degree to which it stops heat escaping from your home) without reducing its g-value.
Using inert gas, such as argon, in the cavity and/or a so-called warm edge spacer bar will improve the insulating glass Ug-value. Using a low-iron glass such as Pilkington Optiwhite™ will improve the g-value. The magnitude of the benefits will depend on non-glass factors such as the frame U-value and percentage frame factor (proportion of frame to glass). Therefore, by combining the best available technologies, it has been proved commercially possible to achieve A-rated windows without the need for triple glazing or costly krypton filling.
With Window Energy Ratings, we have a system which recognises the positive energy gains through windows. This means that windows can be acknowledged as contributors to positive energy efficiency of buildings meaning that legislators and specifiers can stop thinking in terms of reducing window areas. This means the extensive use of glass can easily be incorporated in energy efficient homes.
Window Energy Ratings systems and A-rated windows – Global trends
Window Energy Ratings and A-rated windows are not new ideas nor are they simply British ideas. Window energy rating programmes are already in place in the USA, Canada and Australia & New Zealand as well as other countries. Many other countries are already working on similar schemes to provide energy rating of windows and doors.
The reasons for this are clear; buildings are one of the major users of energy and one of the potential areas of losses in any building is via the glazing. Improving the energy efficiency of windows and doors gives large and lifelong improvements in the energy efficiency of buildings. This has a direct and quantifiable impact on energy-use. Energy-usage is not simply a British problem and countries all over the world are using Window Energy Ratings to improve energy-performance and select A-rated windows for the application.