Replacement Windows Ratings | Explore The Four Key Terms & Measurements


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Replacement Windows Ratings

Find out more about the important replacement windows ratings when it comes choosing the right window options for your home. These ratings are important to determine durability and insulation properties, as well as how energy efficient the window will be.


U-Factor gives you an indication on how much heat loss you can expect from that specific window, this can be through the glass or window frame. The U-Factors offer a number which is normally between 0.2 and 1.3, the lower the better and you can enjoy an energy efficient window.

Silverline 2900 Series: 0.35

Sunrise Resorations Series: 0.27

Soft-Lite Elements Series: 0.19

Air Infiltration

Air Infiltration is often referred to as AI and that rates the air that flows from outside to inside through the glass and frame. This is also shown in a number format from 0 to 0.3, again the lower the rating the less air will make its way into your property.

Vinylmax Hyde Park Series: 0.17

Great Lakes EcoSmart Series: 0.06

HiMark 800 Series: 0.01

Solar Heat Gain Coefficient

Solar Heat Gain Coefficient is also referred to as SHGC and this measures the heat that makes its way through the window frame and the glass. These are shown in a number which is usually between 0 and 1.0. Again the lower the number the better, with lower numbers allowing less heat into the property. Bear in mind that if you live in a colder climate you will probably want a higher SHGC allowing heat into the property and keeping it there, where if you live in a warmer climate you'll want the lower numbers to keep the heat out wherever possible.

Great Lakes Bayshore: 0.48

Visible Transmittance

Visible Transmittance or VT measures the light that comes through your window glass. The numbers range from 0 to 1 with the lower rating allowing less light flow into the home.

Are These Numbers Really Important?

When looking at new windows these numbers can help you determine the performance you can expect from the windows you are looking at. The main numbers are the AI, SHGC and the U-Factor. Ideally the windows you choose should have an AI of .1 or less, a SHGC depending on where you are located and a U-Factor of 0.35 and less.

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