If you’re considering new windows for your home, you may have noticed that there are a lot of terms and features related to energy efficiency. And they’re not always easy to understand without a guide.
Yet it pays to understand these terms and ratings, because they help you evaluate different windows with ease. Navigate these features wisely, and you’ll enjoy a comfortable, efficient home that stays cool in summer, warm in winter, and keeps those utility bills manageable.
Here are the basics of energy efficiency ratings so you can choose replacement windows you’ll truly love.
Energy Star vs. NFRC — What’s the Difference?
You’ll likely see these two terms kicked around as you research different window brands and product lines. But what do they mean?
ENERGY STAR Rating
ENERGY STAR® is a program run by the U.S. Environmental Protection Agency and U.S. Department of Energy. The ENERGY STAR label indicates that a product meets governmental guidelines of efficiency. To earn the label, a window must provide good insulation and prevent the transfer of heat through the glass.
The NFRC Label
The National Fenestration Rating Council (NFRC) is an independent non-profit organization that establishes objective energy performance ratings so consumers can make informed decisions about their replacement windows. The NFRC label defines energy efficiency with specific numbers so you can compare different products effectively.
Energy Efficiency Ratings 101
As you compare windows, you’ll notice several different energy-related terms in their product descriptions, or on the NFRC label. Here’s an overview of what they mean, and how each area can benefit your home.
U-Factor (aka Transfer Coefficient)
What it is: This measurement refers to a window’s ability to act as an insulator between the outdoors and your home’s interior. Features such as low-E (low-emissivity) coatings on glass can help a window’s U-factor be better.
How this benefits you: The longer it takes for heat to be transferred through the window, the more efficient your home will be—because you won’t be losing treated air to the outdoors as quickly. You’ll have more manageable utility bills, and your home will remain comfortable more easily.
What to look for: Low numbers
Solar Heat Gain Coefficient
What it is: This rating measures how effective a window is at blocking the sun’s heat.
How this benefits you: If you live in an area that receives a lot of strong sunlight, a lower SHGc rating means your air-conditioning won’t have to work as hard to keep your home comfortably cool.
On the other hand, homeowners in northern, colder, less sunny regions like ours may benefit from windows with a higher SHGc rating. Such windows allow sunlight to create more indoor warmth, meaning you might not have to turn on your heat as often on winter days.
What to look for: Low numbers for sunny climates, high numbers for cold regions like Chicago
What it is: VT is a measurement that describes how much natural light can come through the window glass. It’s not related to heat transfer, but it will affect how bright your home is. And with today’s glazing technologies, it’s possible to have more sunlight inside without the added solar heat.
How this benefits you: If you like a lot of natural light, windows that allow a lot of visible transmittance are ideal. Also, the more natural light you get, the less often you’ll have to use your electricity to illuminate rooms. This can save you on energy costs.
What to look for: High numbers
What it is: This measurement indicates how much air will come into a room through the window frame.
How this benefits you: Drafty windows are a major concern for many homeowners, as they create a less comfortable home environment and also affect energy usage. Windows that reduce drafts keep rooms cozy and lower utilities costs too.
What to look for: Low numbers
What it is: This measurement relates to how well a window resists condensation. Unlike the other NFRC ratings, this one is optional. Manufacturers may or may not list it in their product descriptions.
How this benefits you: Condensation can be an annoying problem, blocking your view of the outdoors. Choosing windows that resist condensation can keep your glass clear and pleasant to look through—a great benefit when you have beautiful landscaping to enjoy.
What you’re looking for: High numbers
Choosing the Right Windows for Your Home
If you’re located in an area that has cold winters and frequent overcast skies—like we get here in Chicago—you’ll appreciate windows that keep your heat indoors. Look for these energy-efficiency ratings:
- A high VT for more natural sunlight on clear days
- A moderate SHGc to allow heat inside during cold weather
- A low U-factor so your indoor air stays inside, keeping energy bills lower
Those who live in hot, sunny regions tend to benefit from windows that block heat transmission. Look for:
- A moderate VT that permits in natural light without too much heat
- A low SHGc that limits solar heat transference
- A low U-factor to help insulate your rooms
Check out this article to learn more about how the right set of window replacements can help your home be more energy-efficient.
Trusted, Energy-Efficient Window Replacements in the Chicago Area
There are a lot of factors to consider when you’re getting new windows—but an experienced windows company can help you navigate your options with ease.
At Siding & Windows Group, our windows team only does windows—and we know them inside and out. We make you our #1 priority, and we’ll help you balance all your needs and preferences, so you get energy-efficient windows that are the perfect fit for your Chicago home.
Check out our window services—and let us know how we can make your dreams for your home come true.