If you’ve been window shopping lately, you might have noticed that some windows come with a bright blue sticker that verifies them as ENERGY STAR certified. And while this certainly seems like a feature to celebrate, you may not know exactly what an ENERGY STAR window entails—outside of an understanding that it’s energy-efficient and environmentally friendly (even if you’re not exactly sure why).
That’s okay! We’re here to explain precisely what it means for a window to be labeled ENERGY STAR, from the strict guidelines and testing protocols required to approve them to all the financial and comfort benefits they provide.
What Are ENERGY STAR Windows?
How Windows Become ENERGY STAR Certified
It’s not easy for a window to be considered ENERGY STAR certified! In order to do so, it must meet these three requirements:
- Manufactured by an ENERGY STAR partner.
- Tested, certified, and verified by the National Fenestration Rating Council (NFRC).
- Have NFRC ratings that meet the energy efficiency guidelines determined by the Environmental Protection Agency (EPA).
There are five different categories the NFRC tests windows for in order to determine their ratings: U-factor, solar heat gain coefficient (SHGC), air leakage, visible transmittance, and condensation resistance.
The required NFRC ratings differ by region within the United States. There are four regions designated by the NFRC (Northern, North Central, South Central, and Southern) that each have unique, separate rating requirements due to their varying climates.
The Northern region, where Wisconsin is located, for example, requires ENERGY STAR windows with a U-factor score that is less than or equal to .27, while a state located in the Southern region requires a U-factor score of greater or less than .40.
Confused a bit by what all of this means? That’s okay! Let’s learn exactly what these specific NFRC ratings are and what they measure.
How to Read an Energy-Star Window Ratings
Every ENERGY STAR certified window is required to leave the factory with a removable label that shows a product description, certification information, and, most importantly, its NFRC ratings. Here’s what the ratings on those labels indicate:
U-Factor
The U-factor determines how much heat is able to escape through the window. The values will typically range from .25 to 1.25, with a lower score indicating that less heat is escaping.
Solar Heat Gain Coefficient (SHGC)
SHGC measures how much heat passes through your window, and is typically measured on a scale from 0 to 1. Homes in the Northern region, like Wisconsin, will want a higher SHGC score (likely somewhere around .35 to .60) to allow more heat in during the winter, while Southern region homes will want a lower SHGC score to help keep cool.
Air Leakage
Air leakage is exactly like its name—it measures how much air leaks through a window, with a good score being equal to or less than .30.
Visible Transmittance
Visible transmittance lets you know how much visible light passes through a window and can determine how much natural light you get in your home. Scores tend to fall somewhere between .20 and .80, with higher numbers indicating better light.
Condensation Resistance
This is an optional rating that only some NFRC windows will still include, as it measures how well a window prevents the build-up of condensation. The score is reported on a scale of 1 to 100, with a higher score meaning condensation is better kept at bay.
You can expect a typical ENERGY STAR NFRC label to look something like this:
Common ENERGY STAR Features
Although an ENERGY STAR window does not require the use of any specific technologies, there tend to be certain features that are more commonly found in certified products.
- High-Quality Frames: ENERGY STAR windows tend to have durable yet low-maintenance frames (such as fiberglass, vinyl, aluminum, or wood) that reduce the transfer of heat, therefore improving its insulating qualities.
- Low-E Glass: In order to reflect infrared and ultraviolet, most ENERGY STAR windows have low- emissivity (also known as Low-E) glass that is coated with a thin, microscopic layer of metal and silver. It helps keep buildings warm in the winter and cool in the summer.
- Multiple Panes: ENERGY STAR windows frequently have anywhere from two to three or more panes of glass. Not only does this method help with energy efficiency, but it can also help with sound insulation and impact resistance.
- Gas Fills: In between the multiple panes of glass frequently found on ENERGY STAR windows can be gas fills. These non-toxic gases (such as argon or krypton) are both odorless and colorless and have insulating properties.
- Warm Edge Spacers: In order to better insulate the window pane, most ENERGY STAR windows have a spacer that prevents temperatures from fluctuating too greatly around the edges of the window (where air is most likely to enter or escape).
Benefits of Energy-Star Windows
Now that you understand exactly what it means for a window to be labeled as ENERGY STAR, it’s time to unpack all the benefits! All the testing and confusing labels are worth it because, in the end, ENERGY STAR windows offer things such as:
- Cost Saving. Did you know that ENERGY STAR windows can save you an average of 7% to 15% on household energy bills? That comes out to about $71 to $501 a year!
- Environmentally Friendly. By reducing the amount of energy you’re consuming with ENERGY STAR windows, you’re also reducing your carbon footprint.
- Increased Property Value. Upgrading outdated windows to attractive and energy-efficient ENERGY STAR models can increase property value and attract more buyers.
- Added Comfort. A home with ENERGY STAR windows will experience better temperature regulation, increased natural sunlight, and fewer drafts, thereby boosting overall comfort levels.
Contact Us Today
Interested in replacing your single-pane windows with ENERGY STAR certified windows? Then contact us today! Our team of industry experts has years of experience, and we can ensure that your new windows will be installed with care and a dedication to quality. The sooner you get started, the sooner you can start enjoying all the benefits they provide.
