U-Factor? SHGC? Learn How to Read Your NFRC Window Sticker
4 Key Window Efficiency Numbers You Need to Know
Understanding the data on your NFRC window sticker help you choose the right windows and save you money.
So you’re ready to buy new windows for your home, and you know choosing the most energy-efficient replacement window will have a positive impact on both your home’s performance and your wallet. So, which energy-efficient window is the best option? Without the right education, it’s hard to tell.
Uninstalled, most replacement windows look the same when compared side by side. What you can’t see is the science and technology involved in building each window. That’s where the National Fenestration Rating Council (NFRC) comes into play. The NFRC is an independent organization that establishes performance standards for windows and doors, and certifies products based on those standards. The details shared on the NFRC window sticker are your key to understanding your window’s performance and comparing one product to another.
How to Read Your NFRC Window Sticker
All NFRC-rated products are independently tested, certified, and labeled so you can make better apples-to-apples product comparisons. You’ll usually find four numbers on an NFRC window sticker that measure the performance of the window as a unit (not the performance of individual components).
Here’s what they mean:
U factor measures how well the window prevents non-solar heat flow (also called conductivity). Plain and simple, a good U factor means the window won’t let hot air seep into your home during the summer, or let warm conditioned air escape during the winter. Window U factors range from 0.2 to 1.2, and the lower the number, the better.
Solar Heat Gain Coefficient (SHGC)
Abbreviated SHGC, solar heat gain coefficient is U factor’s solar counterpart. SHGC measures how well the window resists unwanted heat gain specifically from the sun. This is especially important during summer cooling season. SHGC ranges from 0 to 1, and the lower the number, the better.
While you want to keep the sun’s heat out, letting in as much light as possible will keep your home bright so you can rely less on artificial lighting. VT, or visible transmittance, measures how well a window allows for daylighting. Ranging from 0 to 1, a higher number is better for visible transmittance.
The Air Leakage (AL) measurement on your NFRC window sticker indicates how much air will enter a room through closed window. Manufacturers are not obligated to report AL, but if they do, the measurement must be 0.3 or below in order for the window to be NFRC-certified. Depending on the state, the NFRC window sticker may show the actual AL measurement, or may simply indicate AL less than or equal to 0.3.
Why NFRC Window Ratings Matter
Windows are not a one-size-fits-all purchase, so understanding NFRC window sticker data gives homeowners a better chance to identify windows that will perform best in their climate.
For example, with hot summers and cold winters in our mixed Ohio/Kentucky/Indiana climate, U factor and SHGC both carry high importance. Meanwhile, homeowners in Phoenix may put more stock in a lower SHGC. In their hot climate, this would keep the sun’s heat from raising indoor temperatures and putting more strain on their air conditioners.
At Improveit, we designed our Performax54 windows for peak performance in the Ohio/Kentucky/Indiana climate. Our stronger window frame, draft-blocking sashes, smart Thermostat glass, and high-efficiency spacers combine to make the ideal energy-efficient windows for our region. Add in our air-tight Installation and a lifetime warranty, and Performax54 windows give you the best possible value in replacement windows.
Schedule a free consultation to learn more about maximizing your home’s energy efficiency – and minimizing expensive energy loss – with Performax54 windows.