You’re building a home and receive an energy rating you need to comply with from your building designer or architect. This is very important! If you are told it does not matter, it will cost you more in the long run! Here’s why…
Windows and doors are incredibly dynamic elements to a home. They need to contribute to keeping a home cool in summer and warm in winter, provide security, fresh air and natural light, whilst demonstrating a sense of finesse. We understand that it is easy to get confused with energy ratings when building a home so we hope this helps you understand it a little better.
Windows react thermally via direct and indirect sunlight. When sunlight hits a window, three activities happen to the heat: reflection, absorption and transmittance.
Reflection is where sunlight strikes a window and some of the solar heat is reflected back. Another activity is that some of the solar heat will be absorbed. Absorption is where the absorbed heat is emitted to the outside and some is emitted inside. The final activity is where remainder of the heat is transmitted through the window into a building.
When selecting aluminium windows and doors for your home, you will often be required to comply with certain performance values for energy efficiency. Complying will guarantee reduced energy bills and a home that is comfortable to live in.
The ability of a window to control heat gain is measured by the Solar Heat Gain Coefficient. SHGC is a measure of how much solar radiation passes through the window. For example, in a cooler climate, windows with a high SHGC allow a greater amount of solar radiation to pass through them which heats up the home.
The other element to rating a window based on the frame and glass is known as the U-Value. A U-Value is the measure of how much heat energy is transferred through a window. Heat can be lost and gained through a window by the processes of conduction, convection and radiation.
The lower the U-Value, the better the window is at keeping the heat or cold out, meaning better energy efficiency. In order to comply with energy reports, U-Values must be lower than or equal to what has been specified in the report.
To make this clearer, high solar gain is important for cold climates. The aim is to reduce heat loss from the interior and allow solar heat through in the winter. The U-Value should be low and the SHGC high.
Low solar gain is important for hot climates. The aim is to keep air-conditioned cool air inside but also reduce heat gain in summer. Both the U-Value and SHGC should be low.
To reduce the amount of direct solar radiation falling on a window you also need to consider the type of glass, the orientation of your windows, and shading – horizontal shading for North, vertical shading for East/West and in a tropical environment, shading for the South.
If you have any questions you can contact your local Vantage® supplier here