We’ve talked about what today’s windows can do for you and your home in part one. Now, let’s discuss what they can do for your energy bill, and the planet as well. When you have energy-efficient windows, you conserve energy. But when your windows are leaky and inefficient at regulating the heat and light that comes into your home, they account for more than 25% of your energy usage (according to the US Department of Energy). The best way to cut costs as well as keep an environmentally-conscious home is to look for the National Fenestration Rating Council, or NFRC, label and pay attention to these energy performance ratings.
U-Value measures the rate of heat transfer of your windows. The lower the value, the less heat escapes through the glass. Those living in cooler regions will find increased insulation performance of a window with low U-Value.
Meanwhile, Solar Heat Gain Coefficient (SHGC) is the measure of how much solar radiation a window admits. Products with low SHGC benefit those living in warmer regions as this indicates less heat is being transmitted into your home, thus keeping your house cool. High SHGC values, on the other hand, are ideal for heat collection during winter.
Visible Transmittance (VT) indicates how much light is let through — the higher the VT, the more daylight the window lets in.
The lower the Air Leakage (AL), on the other hand, the less air passing through joints and gaps in the window assembly.
Condensation Resistance measures how well the window resists water build-up. Moisture formation in your windows can lead to mold, mildew, and rotting wood sills. As this is an optional label to display, some window manufacturers may opt not to include this information.
But how do you know you’re getting the most out of your window’s energy efficiency? These values, after all, depend on a number of things: quality of the materials used, type of materials used, engineering and design of the window, and quality of assembly. As important as it is to pay attention to the materials, proper installation also plays one of the biggest roles in optimal thermoregulation and energy efficiency of your windows. And that’s what we will cap off this series with in our next installment. Stay tuned!