What to know about replacement window energy efficiency ratings

What to Know about Replacement Window Energy Efficiency RatingsReplacement windows are a great way to improve the energy efficiency of your home. But how do you know which windows are the most efficient? The answer lies in the window’s energy efficiency rating. In this article, we’ll discuss what you need to know about replacement window energy efficiency ratings so that you can make an informed decision when selecting new windows for your home.

What is an Energy Efficiency Rating?

An energy efficiency rating is a measure of how well a window performs in terms of its ability to keep heat in or out of your home. The higher the rating, the better the window will be at keeping your home comfortable and reducing your energy bills. The most common type of energy efficiency rating is the U-factor. This measures how much heat is transferred through a window, with lower numbers indicating better performance. The U-factor is usually expressed as a number between 0 and 1, with lower numbers indicating better performance. Another important factor to consider when looking at energy efficiency ratings is the Solar Heat Gain Coefficient (SHGC). This measures how much solar radiation (heat) is allowed into your home through the window. A lower SHGC indicates that less heat will enter your home, making it more comfortable and reducing your cooling costs.

How Do I Choose an Energy Efficient Window?

When choosing an energy efficient window, it’s important to look for one with a low U-factor and SHGC. Generally speaking, windows with a U-factor of 0.30 or lower and an SHGC of 0.25 or lower are considered to be very energy efficient. It’s also important to consider other factors such as frame material, glazing type, and air leakage rate when selecting an energy efficient window. For example, vinyl frames are generally more energy efficient than wood frames because they don’t absorb as much heat or cold from outside temperatures. Similarly, double-glazed windows are more efficient than single-glazed windows because they provide an extra layer of insulation against temperature changes outside your home. Finally, it’s important to look for windows with a low air leakage rate. Air leakage occurs when air passes through gaps around the edges of the window frame and can lead to increased heating and cooling costs if not properly sealed. Look for windows with a low air leakage rate (less than 0.3 cfm/ft2) for optimal performance.

What Are Some Common Energy Efficiency Ratings?

There are several different types of energy efficiency ratings used by manufacturers today, including ENERGY STAR® ratings and NFRC ratings. ENERGY STAR® ratings are based on specific criteria set by the US Environmental Protection Agency (EPA) and indicate that a product meets certain standards for energy efficiency and performance. NFRC ratings are based on testing conducted by the National Fenestration Rating Council (NFRC) and provide information about a product’s U-factor, SHGC, visible transmittance (VT), air leakage rate (AL), and condensation resistance (CR). ENERGY STAR® ratings range from 0-100, with higher numbers indicating better performance in terms of energy efficiency and comfort levels inside your home. NFRC ratings range from 0-5 stars, with 5 stars indicating superior performance in terms of U-factor, SHGC, VT, AL, and CR values compared to other products on the market today.

Are There Any Other Factors To Consider?

In addition to considering energy efficiency ratings when selecting replacement windows for your home, there are several other factors that should be taken into account as well:

  • Cost: Make sure you compare prices between different brands before making a purchase.
  • Durability: Look for windows made from materials that are designed to last.
  • Style: Choose windows that complement the style of your home.
  • Installation: Make sure you hire experienced professionals who can install your new windows correctly.

It’s also important to remember that even if you choose an energy efficient window with high ratings, it won’t perform optimally unless it is installed correctly and maintained regularly over time. Be sure to follow all manufacturer instructions carefully when installing new windows in order to ensure maximum performance and longevity.


Replacement windows can be a great way to improve the energy efficiency of your home while also adding value and style at the same time. When selecting new windows for your home, it’s important to consider their energy efficiency ratings in order to make sure you get the best possible performance out of them over time. Be sure to look for windows with low U-factors and SHGCs as well as other features such as durable frames and low air leakage rates in order to maximize their potential benefits for years to come!

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