Buying New Windows? The 2 Most Important Factors To Look For

13 November 2015
 Categories: Construction & Contractors, Articles


When the time comes to replace your old windows, you may have no idea how to choose the right windows to replace them with. There are many window manufacturers and types of windows to choose from, but understanding window ratings can help you select the best type for your needs. The National Fenestration Rating Council (NFRC) is the organization responsible for placing ratings on all windows, and they use a variety of different ratings to measure the strength of a window. Here are the two most important factors you may want to look for when you choose new windows for your home.


The first rating to understand is called the u-factor, and this is one of the most important ratings to look at when choosing windows. The u-factor of a window is a rating that tells you how well a window is at resisting heat flow. The u-factor is basically a rating used to understand the insulating properties of a window.

Windows that are great insulators will stop most heat flow. In other words, a window that has a great u-factor will not allow heat from your home to escape through the windows. U-factor ratings generally range from 0.15 to 1.20. Higher u-factor ratings represent insulating qualities that are not very good, while lower u-factor ratings represent windows with great insulating power.

As you look at windows, you may notice that single-pane windows have the highest u-factor ratings. This occurs because single-pane windows have only one sheet of glass in them. Double-pane windows typically have u-factor ratings that are around 0.30, or even lower. If you choose triple-pane windows, you are likely to find the best and lowest u-factor ratings, which can be around 0.15.

Double and triple-pane windows have better insulating qualities because they contain two or three sheets of glass, and there is a layer of gas in between these sheets. If you want windows that are highly efficient, you should look for a u-factor rating that is around 0.30 or lower.

Solar Heat Gain Coefficient

The second factor that plays a huge role in the efficiency of a window is the solar heat gain coefficient (SHGC) rating. This rating is used to measure how well the windows block heat from the sun. You will notice with SHGC ratings that they are between 0 and 1. Just like with u-factor ratings, lower SHGC ratings stand for better abilities to block heat from coming through. For example, a window with an SHGC rating of 0.20 means that only 20% of the solar heat from the sun will get through the window. One with a rating of 0.80 will allow 80% of the solar heat through.

Before you rush out and look for windows with a low SHGC rating, it is important to understand that your climate can play a role in the SHGC rating you look for. If you live in an area that is cold and requires heat for most of the year, the SHGC rating is not as important. This is because you would want your windows to let heat come through, because this could help heat your house in cold months.

On the other hand, if you live in an area that is hot most of the year, finding windows with a low SHGC would be the best option. This would stop excess heat from coming in, which would allow you to cool your home easier.

If you purchase the most efficient windows for your home, it could help you save money on heating and cooling costs. To learn more, contact a contractor, such as Fas Windows and Doors, that sells replacement windows today.