Choosing Energy Efficient Replacement Windows

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Replacing windows is a significant, long-term investment for homeowners, so choosing the right windows among the plethora of options available today is extremely important. Yet weeding through replacement window choices at your local home improvement center or window dealer showroom can be intimidating. Luckily, the National Fenestration Rating Council (NFRC) is here to help.

NFRC’s residential window labels can help consumers quickly compare the energy performance of windows, doors, skylights, and other fenestration.

U-Factor and Solar Heat Gain Coefficient

So, what do you look for when choosing the right replacement window for your climate? Two of NFRC’s ratings should be top of mind: U-factor and Solar Heat Gain Coefficient (SHGC). By understanding these ratings, you can make an informed decision when comparing energy efficient replacement windows, which can help save you money on heating and air conditioning costs.

U-factor measures how well a window prevents heat from escaping a building and is rated from 0.09 to 1.20. The lower the U-factor, the better the product is at keeping heat from escaping.

Solar Heat Gain Coefficient, or SHGC, measures how well a window blocks the sun’s heat, and is rated on a scale of 0 to 1. The lower the SHGC, the better a product is at blocking unwanted solar heat gain.

Before heading out to purchase your new replacement windows, contact your local building permits department to inquire about your community’s energy requirements for residential windows. Having this information on hand will make your purchasing decision simpler as you will know which product’s ratings comply with local energy codes.

When you are finally ready to purchase your replacement windows, look for the NFRC rating label on each window to compare products. Like the gas mileage sticker on a new car, these labels allow you to quickly compare which windows are in the specific rating range that you need. If there is no NFRC label, the product has not been NFRC certified.


For more than 20 years, consumers, architects, contractors, and building code officials have trusted NFRC’s ratings. For windows, NFRC is the only independent tester and provider of ratings. In fact, to be eligible for ENERGY STAR®, windows must first be NFRC rated. NFRC’s focus on uniform, accurate, and unbiased ratings makes it the recognized leader in arming consumers with the energy performance information they need for windows and other fenestration products.

For more information on windows, the NFRC Label, and NFRC, visit