Choosing Energy Efficient Windows
If eyes are the windows to the soul, then surely windows are the eyes of your house, right? Something like that, anyway. When it comes time to replace those windows, it’s important to make a carefully considered decision before pulling the trigger. Today’s modern windows come in a staggering number of designs, made from a lot of different materials, all with different ratings to help you better understand their performance.
Choosing the Best Windows for the Job
The good news is that there’s no one window that’s perfect for your home, so you’ll have plenty of options. There will probably be many different types and styles to choose from, with features that will help you improve your energy efficiency and keep your home cool in the summer and warm in the winter. Start by choosing the window style and cladding materials you want. Once you’ve settled on that, you’ll find yourself toe to toe with the NFRC label.
What’s on an NFRC Label?
The NFRC label is a useful sticker developed by the National Fenestration Rating Council to help you better understand what you’re getting from your window purchase. It contains lots of useful information, and if you know how to decode it, you can learn a lot about how your new windows will behave in all kinds of weather.
Here’s what you’ll see on the label:
- U-Factor. The U-factor tells you how much heat your window will lose when compared to other windows. A lower number means that there’s less heat flow between the glass, with values as low as 0.30 for double-pane windows and 0.15 for triple-pane windows. This measurement is only for non-solar heat flow, so don’t hesitate to go for a low U-factor if your home relies on passive solar for heating.
- Solar Heat Gain Coefficient (SHGC). If you do have a passive solar home, this part of the label is going to be really important for you, because it shows how much solar radiation can pass through the window to be released into your home. A low SHGC rated window transmits a lot less radiation and is better at acting as a shade in the summer. High SHGC windows allow more radiation to pass through the glass, adding more heat to your home. Low SHGCs are excellent for super hot and sun-intense areas like the desert southwest, whereas high SHGCs are perfect for homes that don’t experience intense summer heat but might benefit from the extra heat being transferred indoors in the winter.
- Visible Transmittance. Do you like lots of indoor light? Most people do, but it’s not perfect for every spot. That’s why windows have options! Visible transmittance refers to how much light visible to the human eye is allowed to pass into interior spaces. This rating ranges from 0 to 1, with 0 transmitting the least amount of light and 1 transmitting the most.
- Air Leakage. Drafty windows are almost a feature of older homes with older windows, but they don’t have to be with tightly designed, properly installed new windows. A higher number indicates more air leakage, a lower one means less. This number is based on the windows being installed correctly, which is sometimes difficult for a homeowner to do on their own, so be sure to ask for advice to get the most value from your purchase.
- Condensation Resistance. Condensation forms on a window when moist air hits window glass that’s significantly cooler. A high number tells you that your new windows are highly resistant to condensation. Although condensation is mainly a cosmetic issue, it can lead to longer term problems. So if that’s a major problem where you live, you’ll want to give this part of the label careful consideration.