Whether it’s keeping the frigid winter outside or pleasant air-conditioning inside, a properly installed window can be the first line of defense in weatherizing your home. Modern window glass is tempered, layered, and has gas injected between layers. These manufacturing techniques have led to a wide variety of products which are regulated and certified by the NFRC (National Fenestration Ratings Council). “Fenestration” sounds scary but it’s just a fancy word for the arrangement of windows and doors on a building.
Do I need to replace my windows?
That draft you’re feeling is more than likely coming from a bad seal in your windows. An easy DIY way to check is to hold a candle to the frame and look for the flame to flicker. Like most home improvements, identifying the problem is the easiest step. A quick first glance at NFRC ratings can be a little intimidating, but we expect windows to perform many different duties and so the NFRC rates on many different categories.
Air leakage (AL) is a measurement of how much air passes through a window assembly. This is your primary culprit for that draft that’s bugging you. An Energy Star certification requires an AL of 0.3 or less. Now, an Energy Star certification is all well and good, but professional installation is the only way to ensure that your product’s real-world performance will live up to its rating.
A window’s insulation is rated by the U-Factor. A lower U-Factor means the window is better suited to resist heat escaping. Modern windows are double-paned, or even triple-paned to achieve a lower U-Factor and keep your heating bills down in the winter. This flow of heat varies depending on different climates and Energy Star provides recommendations of the ideal U-Factor for any given climate.
Solar Heat Gain
This is one of the more complicated tasks we ask of a window, but it boils down to what we know about how greenhouses work: hot sunlight passes through glass, the glass absorbs some heat, and the rest gets transmitted and trapped inside. The NFRC measures how well a window resists this solar radiation by the SHGC (Solar Heat Gain Coefficient). A lower SHGC means more solar heat gets reflected or absorbed, and less solar heat passes through a window into the room. While free heat from the sun can be nice in winter, it means you will face overheating in the summer and will constantly be cranking up your AC. A contractor will know the best balance of solar heat gain for your home based on climate, orientation, and shading conditions.
CR (Condensation Resistance) is an optional rating for manufacturers to include and is primarily cosmetic, but failing to take it into account, especially in humid climates, will mean living with unsightly and hard-to-remedy condensation on all of your windows. A higher CR means less cloudy, foggy windows. It should be noted that because the value is optional to include on manufacturer’s stickers, a window without a listed CR isn’t necessarily bad at condensation resistance.
VT (Visible Transmittance) measures how much visible daylight enters a room. Daylight is the cheapest, most pleasant, and desirable way to light a room, but all the bay windows in the world won’t take the best advantage of daylight unless they have a strong VT. Modern glazing systems can actually block out solar heat while maximizing visible light, allowing for the best of both worlds. A higher VT means more daylight and less money spent on electrical lighting.
Pays for itself
Outdated, poorly-installed windows can lead to higher bills in the winter, higher bills in the summer, higher bills during the day, higher bills during the night, and ultimately a lower resale value. A one-time window renovation will not only lower your bills and increase your home’s value, but it will directly and noticeably improve your quality of life. Canvas Your Home will help you identify the conditions that most commonly prevent optimal window performance and will connect you with the contractor who can best perform the solution.