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If you’re in the market for replacement windows in Texas, you may be hearing about the U-Factor a lot. But what does this mean? According to, U-factor refers to the rate at which a door, window, or skylight will transmit non-solar heat flow. Put another way, it’s the most important insulation rating for your new windows, representing the amount of heat that passes through them.

There are many regulations and certifications in place designed to determine the quality of a window. U-factor is one of those, and you will find that number on your window’s NFRC sticker. NFRC stands for National Fenestration Rating Council, which lists the U-factor as a measure of the rate of heat loss of the whole window assembly. The best insulating factors are awarded to windows featuring superior resistance to heat transfer. The lower the U-Factor number, the better rated the window is.

So, in a perfect world, you want to choose replacement windows with the lowest U-Factor rating you can possibly get. This will help you save the most money on your energy bills over time. Not all numbers are created equally across the board, though. The value will vary with the climate in which you live.

In hotter climates, replacement windows with a lower U-Factor are more desirable. If you live in a colder climate, you still want a lower U-Factor but you can get away with a higher one in that type of environment.

U-Factor vs. R-Value

Maybe you’ve heard these two terms before. They are similar but have a key difference. While the R-Value also involves insulation and heat flow resistance, it has nothing to do with windows. Rather, it reflects how well your roof, floors, and walls are insulated. Opposite of U-Factor, a higher R-value is desirable because it represents better insulation.

About the NFRC

The U-Factor is a rating created by the National Fenestration Rating Council, which is responsible for testing, certifying, and labeling products like windows, skylights, doors, and building components. They aim to educate consumers on the energy efficiency and quality of those products. The NFRC label will display not only the U-Factor, but also elements like air leakage, condensation resistance, visible transmittance, and solar heat gain coefficient.  

As you know, there are many parts of a window, and each one works together to determine the U-Factor, from the glazing to the frame to the spacer.

So, how do you know if you’re buying replacement windows in Houston with a low U-Factor? A good rule of thumb is to shoot for a U-Factor of .30 or lower, which is an indication of the highest quality and max performance-rated windows. But there are even lower U-Factor ratings out there, such as the newest double-pane and triple-pane windows at .15.

Here at Amazing Exteriors, we carry energy-efficient, low U-Factor-rated replacement windows to meet your needs.

Contact Amazing Exteriors for Energy Efficient Replacement Windows in Texas

To learn more about the U Factor of our replacement windows and how we can help your home become more energy efficient, contact us today at 512-428-8417.

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