How to Read a Window Energy Efficiency Label (And Save Money on Your Energy Bill)

May 9, 2025
An ad for second city roofing and exteriors shows a man cleaning a window

Windows can have a huge effect on the energy efficiency of your home, and if you want to save money on your energy bill, it's important to choose windows with an energy efficiency label. But how do you read one? In this blog post, we'll explain what each part of the label means so you can make an informed decision when shopping for windows. We'll also give you tips on how you can save money on your energy bill by making windows replacement. Read on to learn more!

U-Factor

It is important to pay attention to the U-Factor of your windows when shopping for new ones, as it can have a big impact on the comfort level of your home and the amount of energy used to maintain a comfortable temperature. The U-factor measures how much heat moves through a window. Generally speaking, the lower the U-factor number, the better insulated the window is and the more energy efficient it will be. Additionally, windows with higher U-Factors may require additional insulation, such as weather stripping and caulking, to help reduce energy loss. Furthermore, many local utility companies offer incentives or rebates for buying more energy-efficient windows to encourage homeowners to save money on their bills. Make sure to check with your local utility company before making any purchases so you can get the most out of your window upgrades. 

Solar Heat Gain Coefficient (SHGC)

Another thing to consider when choosing windows is the solar heat gain coefficient. For example, if you live in a place with a warm climate, you may want to block out as much of the sun’s energy as possible. Windows with higher SHGC ratings will let more sunlight and heat in, while windows with lower SHGC ratings will be better at keeping out the sun’s energy.


In addition to helping keep your home cool during the summer months, an SHGC rating can also have an effect on your heating bills in the winter. By blocking out the sun’s rays during the summer months, you may be able to reduce your cooling costs. On the other hand, windows with higher SHGC ratings may allow more sunlight into your home during the winter months, which could help reduce your heating costs. 


It’s important to remember that there’s no one-size-fits-all when it comes to selecting an SHGC rating. You should consider your climate, home design, and orientation in relation to the sun when choosing an appropriate SHGC rating for your windows.

Visible Transmittance (VT)

When considering a window energy efficiency label, make sure to also look at the visible transmittance rating. You can use this to determine if the window allows enough natural light into your home. Higher VT ratings mean more natural light will enter your home, which can help reduce the need for artificial lighting and save energy. Lower VT ratings can mean less natural light and higher energy bills. If you want to conserve energy and reduce your energy bills, look for a window with a higher VT rating.

Air Leakage (AL)

Next to consider is air leakage. Air leakage measures how much air can flow through the window. Air leakage is typically expressed in cubic feet per minute (cfm) at a given pressure difference across the window, such as 0.3 or 0.1. The lower the number, the better the window is sealed and insulated from the outside air. If a window has an AL rating of 0.3, that means that it will allow 300 cubic feet of air to pass through the window each minute at a pressure difference of 0.3.


It’s important to understand the importance of air leakage when selecting windows for your home. Leaking air can cause drafts and make rooms uncomfortable, or lead to higher energy bills due to wasted energy. A good air leakage rating helps to ensure that your home is well-insulated and comfortable throughout the year.

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Condensation Resistance (CR)

The last factor to consider is condensation resistance. Condensation Resistance is a measure of the ability of a window to resist condensation build-up on its surface. Condensation can be caused by interior humidity, weather changes, or contact with other objects like hot and cold air. The higher the CR rating, the better the window’s ability to reduce condensation buildup. The Condensation Resistance is measured on a scale from 1 to 100, and the higher the rating, the more resistant the window is to condensation. 


When shopping for windows, it’s important to pay attention to the CR rating as well as other ratings such as U-Factor and SHGC. A window with a high CR rating will help keep condensation off of your windows and ultimately reduce your heating and cooling bills.

Conclusion

Understanding window energy efficiency labels is a key part of making sure that you have the most efficient windows in your home. By knowing the U-Factor, SHGC, VT, AL, and CR, you can be sure that your windows are helping to keep your energy costs down. By selecting energy-efficient windows, you can help reduce your energy bills and make your home more comfortable. Additionally, you may also qualify for rebates or other incentives offered by your local utility company. Taking the time to learn how to read a window energy efficiency label is an important step to ensuring that your home is as efficient as possible.

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