Discover Replacement Window Ratings


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Replacement Window Ratings

Replacement window ratings are some of the most important factors that come into play when selecting the best replacement window for your home. The numbers indicate how well the window is designed and built, as well as how effectively it keeps out air and moisture.

For some consumers, these ratings are too technical and confusing (which they can be for a number of reasons). These consumers will need to rely on finding a good contractor who can suggest manufacturers and models that will provide good long term protection to the home.

For those consumers who are interested in replacement window ratings, pay particular attention to four measures; U-Factor, Air Infiltration, SHGC and Design Pressure. There are many more performance numbers in the industry, but for 95% of all residential homes, knowing these four will be more than sufficient.


U-factor (also known as U-value) is a measure of Energy efficiency plays a very important role in your window selection and the U-Factor rating that each window provides tells you what the heat loss will be. Most windows range between 0.2 and 1.3, the lower the rating the better your energy efficiency will be.

Some examples include:

Silverline 2900 Series - 0.35 (not very impressive)

Sunrise Restorations - 0.27 (impressive)

Soft-Lite Elements - 0.19 (outstanding)

Air Infiltration

Air infiltration or AI is the rating used to determine the air that leaks into the property from the outside through the window glass or the window frame. Most windows will rate their AI between 0 and 0.3, the lower the rating the less air will leak into your property.

Some examples include:

Vinylmax Hyde Park - 0.17 (not very impressive)

Great Lakes EcoSmart - 0.06 (impressive)

HiMark 800 Series - 0.01 (outstanding)

Solar Heat Gain Coefficient (SHGC)

The SHGC measures the heat that can work its way through the window glass and frame into the property. The normal ratings are between 0 and 1.0 with the lower rating being the better option if you live in a warmer climate. These ratings will help you determine how much heat will be allowed into your property on a hot summer's day. If you are using air conditioning, you don't want heat filtering through your windows and heating up the area, making your air conditioning work overtime. At the same time homes in cooler climates will want higher SHGC ratings than warmer climates.

Visible Transmittance (VT)

VT is the measurement used to determine how much light each window allows to flow through the glass. Average numbers are between 0 and 1, the higher the rating the more natural light will be allowed to flow into the room.

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