When it comes to installing new windows, you want to ensure that they will perform brilliantly in your home. After all, poor window performance can account for over 50% of heat loss in a home in Winter and can allow hot air to enter your air conditioned home in the Summer months.
So, how do you start to understand window performance, and just what is WERS?
Short for Window Energy Rating Scheme, WERS is a scientifically based and credible rating system which enables you to assess products for their energy efficiency performance.
WERS helps to simplify the tricky world of window comparison with a simple star rating system for the performance of residential windows. These star ratings are based on a window’s performance which includes its U-value and its SHGC (Solar Heat Gain Coefficient).
- U value: this measures how readily a window is able to conduct heat. The best performing windows will be those with the lowest U value as this shows a greater resistance to conductive heat flow. These values will usually be between 8-1 with 1 being the best.
- SHGC: this helps to measure a window’s ability to control the heat transfer from solar radiation. It’s expressed as a number between 0-1 with the lower numbers representing windows that do not transmit as much solar heat. These values will usually range from 0.75 to approx. 0.15. With SHGC, it’s not as simple as lower scores being bad or good, it’ll depend heavily on the climate and building location, and whether the window is appropriate for that setting.
Remember that a window is generally made up of a number of parts such as the frame, glass and spacer bar – the WER helps to combine these different aspects and give a whole window energy rating.
Understanding Heat Gain and Loss
There are a number of ways that heat can be gained or lost through windows. This becomes a problem in the warm Summer months when you want your home to be cool, or in the Winter when you are spending money on electricity and gas to heat your home.
Some of the ways in which heat can be lost or gained through windows includes;
- Direct conduction through the glass
- Air leakage through and around windows (especially with broken or poorly maintained frames)
- Radiation of heat into a house from the sun
- Radiation of heat out of a house from people, furniture and interior walls
When it comes to environmental benefits and energy efficiency, windows with high WERS are usually considered the best.
A window that has a high WER will be able to help you to reduce the amount of energy (either gas or electricity) which is needed to heat or cool your home. This can reduce your carbon emissions by a substantial amount.
Efficiency properties aside, there are several other factors you may want to consider when it comes to your windows and how you want them to perform.
- Many people fail to consider security – despite the fact that the majority of break ins are made through the windows in people’s homes. Remember that the energy rating of a window has no correlation to how safe or secure it is so you’ll need to consider this separately.
- Windows that fit with the style and design of your home – always consider the right choice for your individual property and the aesthetic that you prefer.
- Think about the weather conditions in your specific area – if you live in an area subject to a wet climate, then certain materials may be more appropriate than others, and similarly with extremely hot and dry locations. Factors such as large surrounding trees that cast a lot of shade on your home will also be useful to think about.
If you would like more information or advice regarding window performance and selecting the most appropriate products for your home, contact us today.