Understanding Your Energy Efficient Windows Rating | Dallas, TX
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Energy performance ratings can be attributed to windows, doors, and skylights built into your home. The most important thing these ratings can tell you is how much heat may be gained or lost through your windows, as well as how much sunlight will be transmitted into your home.
When looking for energy efficient windows, there are two main ratings you should look out for: the Energy Star label, and the National Fenestration Rating Council (NFRC)’s label.
So what can the Energy Star label tell you?
The Energy Star windows program was initially created by the Department of Energy in conjunction with the U.S. Environmental Protection Agency to provide a method of allowing consumers to identify windows that are energy efficient quickly.
To achieve an Energy Star designation, a window must have both U-factor and Solar Heat Gain Coefficient (SHGC) numbers that fall below specified values. In North Texas areas, such as Dallas, superior U-factors are considered to be < 0.50 and < 0.30 for glazed windows. Windows are considered to be energy efficient windows and meet Energy Star designation if their measured U-factor falls below this value. Likewise, the SHGC must be below < 0.30 in Central Texas to be considered eligible.
Low values, especially a low SHGC value, reduce the requirement for additional cooling in the summer, but it also reduces the amount of free solar heat gain in winter. If your home racks up high air conditioning costs during the summer months, it’s best to install a window with values of 0.25.
What do these Energy Star values really mean?
Well, the U-factor is the rate at which a window, skylight, or door conducts non-solar heat. How much heat is lost or gained is represented as a number between 0.25 and 1.25, and the lower the value, the more energy efficient the window is. On energy efficient windows rated by Energy Star, these values refer to just the glass or glazing. If you’re looking at an NFRG label, these values represent the entire window performance, including the spacer and frame.
The SHGC value of an Energy Star rating is the fraction of solar radiation that is transmitted through a window, skylight, or door – either directly or absorbed and subsequently released later as solar heat. The lower your SHGC value, the less solar heat the interior of your home receives, and the more considerable amount of cooling or shade your Dallas, TX home will experience indoors. It’s typically expressed as a unit between 0-1. The lower the number, the more useful your window will be for reducing the cooling strain of your air conditioning in the summer, as less of the heat gain from the sun is retained through the glass.
Aside from Energy Star, the National Fenestration Rating Council (NFRC) also has a valuable window rating system that can help the average consumer to identify the most energy efficient windows. Their voluntary program tests, certifies, and labels not just windows, but also doors and skylights based on their energy performance. It’s a more comprehensive method of assessing windows than just checking for the Energy Star sticker on your potential purchase, and it helps to provide a robust comparison between energy efficient windows when you’re looking for your next window choice.
What’s the difference between Energy Star rating and NFRG ratings?
Energy Star is an efficiency rating based solely on the U-factor and solar heat gain coefficient ratings mentioned previously. NFRG measures visible transmittance, air leakage, and condensation resistance in addition to the U-factor and SHGC value that Energy Star measures.
Visible transmittance is the amount of visible light that will enter your home. The scale for visible transmittance values ranges between 0 and 1. The lower the number, the less light can transfer through the window. Depending on where your home is, and the type of light it receives, you may want to choose higher or lower based on your preference. If you’d like more natural light, opt for energy efficient windows with high visible transmittance. If you want to make sure your home stays cool in the summer months, a lower visible transmittance figure is recommended.
Air leakage is, as the name suggests, the amount of air that will pass through your window. If your home is particularly exposed to high winds, a lower air leakage rating is preferable. These values usually range from 0.1 to 0.3, with 0.1 preferred for homes in windy areas.
Heat can be lost or gained through your Dallas, TX home, from several sources. Direct heat conduction through glass, glazing, door frame, or door, radiation into the house from direct sunlight, and out of the home from appliances or people, as well as air leakage through or around windows, can cause changes in temperature. Energy efficient windows will not only help you to save money on the air conditioning or heating bills, but it can also keep your home a more comfortable ambient temperature year-round.
Condensation resistance is also measured as part of the NFRG rating process. This figure is an indication of how much moisture can build up on your window’s surface. It’s measured on a scale between 1 and 100. The lower the number, the more condensation you can expect to see. A smaller number may lead to more maintenance required.
What type of energy efficient windows do you need on your TX property?
Certain windows of your home may see more direct sunlight than others, depending on which way the property is facing. For windows that see a lot of direct light, energy efficient windows with lower U-values and SHGC measurements are the best choice.
Not every manufacturer will test and certify their windows with both Energy Star and NFRG, and there are also other certification labels to look out for, so you may not see these values. If you’re unsure which type of window would be the best option for a particular room in your home, contact Energy Window Solutions for an accurate assessment and advice regarding available options.