Window Energy Labels Simplified

Your home is an investment!

It’s usually the biggest investment you’ll make. If you are anything like me before you make a purchase, you want to make sure the product is going to last a long time, and you’re getting value for the money you spend. When it comes to window replacement that means you should be looking at performance ratings. You’re in luck; the Energy Star label provides you all the information you need to determine how energy efficient a replacement window is.

If you’re like most people though, the sea of information on the Energy Star label makes the decision of selecting a replacement window confusing!

Don’t panic! We are here to help you make sense of it all!

Before we go into the numbers there are a few things to know:

  • Energy Star ensures quality by holding replacement window manufactures to strict standards set by the National Fenestration Rating Council (NFRC).
  • Standards vary based upon Climate Zone. In Wisconsin, we are in the Northern Climate, which emphasizes insulation and durability.
  • To be Energy Star certified you must meet the minimum requirements.

Let’s look at the Energy Star label for window replacement, section by section.

Energy Star Label for Replacement Windows
**Pictured – AHT Wisconsin Window Energy Star label

U-Factor:  This measures how well a product keeps heat from escaping a room. Also called U-Value or thermal transmittance. The lower the number, the better the product is as keeping the heat inside the room and the less you’ll spend on heating costs in the colder months.

=Look for: Low numbers

Energy Star Minimum: ≤0.27


SHGC: This stands for Solar Heat Gain Coefficient and measures how well a product resists unwanted heat gain, mainly important in the warmer months. The lower the number, the less you’ll spend on cooling costs in warmer months.

Look for: Low numbers

Energy Star Minimum: Any in the Northern Region but can range between ≥0.32 and ≥0.42


Visible Transmittance: This measures how well a product lights your home with daylight – potentially saving you money on lighting costs. The higher the number, the more natural light is allowed through the window.

Look for: High numbers

Energy Star Minimum: No requirement


Air Leakage: This measures how much air a product allows to enter a room. The lower the number, the fewer drafts you’ll feel.

Look for: Low numbers

Energy Star Minimum: ≤ 0.30 cfm/ft2


AHT Wisconsin Windows sells windows build specifically for our Wisconsin weather. Why does this matter?

Not only do we meet the minimum Energy Star requirements – we exceed them!

In fact, AHT Wisconsin Windows has been recognized as selling Energy Star’s Most Efficient Window in 2017, making this the 5th consecutive year we’ve had this honor!

We know purchasing replacement windows is an investment you only want to do once,Reduced Energy Costs which is why we have a 50-year warranty. Once you replace your windows with us, you won’t have to worry about replacing them again.

Call us today at 866-367-6560 to schedule a free, no-obligation consultation with our experts to hear more about how we can make window replacement comfortable for any budget.

Click here to take advantage of special savings before your appointment.