Our nation is a great big puzzle of different climates. Some areas are lucky and don’t see a single day of freezing during the winter, while other areas could have snow piled against their house that completely covers their windows. During the summer there are areas that consistently stay well above 100 degrees, and others that never see a day above 80 degrees.
Each different climate requires building construction and windows that are best suited for the temperature and weather in that area. So the windows that are used in homes in Texas or Florida may not be the best choice for homes in Cincinnati. This is especially true of energy-efficient windows.
To determine the energy efficiency of window and what climate they are best suited for they are tested and then assigned a SHCG rating and a U-Factor rating by the National Fenestration Rating Council. What do these ratings mean? Glad you asked.
SHGC Rating for Energy-Efficient Windows
SHGC stands for Solar Heat Gain Coefficient and it measures how much of the sun’s heat the window allows to come in the house from the outside. For homeowners that live in the cooler climates up north, they want the SHGC number to be high. The higher number means that more of the sun’s heat is getting in the home and is being heated naturally by the sun.
Of course, homes in southern climates need to have energy-efficient windows that are the exact opposite. They need windows with lower SHGC numbers that keep the sun’s heat out so their homes don’t get any warmer than they already are.
U-Factor Rating for Energy-Efficient Windows
The U-Factor rating measures the exact opposite of what the SHGC rating measures. Instead of measuring how much of the sun’s heat gets in the house from the outside it measures how much heat escapes out the window from the inside of the home. The ratings for the U-Factor range from 0.2 to 1.2, with windows that have ratings closer to 1.2 being the ones that allow more heat through.
Climate Zones for Energy-Efficient Windows
Now that you understand what each of the ratings mean, you have an idea of what ratings you are looking for on your energy-efficient windows. As you can see on the rating chart, the country is broken down into 4 climate zones. To help you determine what climate zone you are in and what ratings you should be looking for you can use the Energy Star Climate Zone Map.
You can also contact us and we will gladly help you pick out the perfect energy efficient windows for where you live.
