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Understanding The Solar Heat Gain Coefficient When Window Shopping

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Replacing the windows in your home is a large investment.  New windows can add value to your home, give your home a new look, and save on energy.  When purchasing new windows, consumers will want to find a window that meets their needs and that are energy efficient:

What is Energy Star?

Energy Star is a program that the Environmental Protection Agency (EPA) started in the early 1990's in order to conserve energy.  Windows that are Energy Star certified meet certain criteria set forth by the EPA and the Department of Energy (DOE).  When purchasing windows, it is in the consumer's best interest to find windows with the Energy Star label.  These windows will help reduce energy bills, which in turn is better for the environment. 

Solar Heat Gain Coefficient

In order to have an energy efficient window, there are several things to consider.  One of them is the solar heat gain coefficient.  The solar heat gain coefficient is the amount of solar radiation that is let into the home through the window and then released as heat in the home.  It is given as a number between zero and one. 

Understanding the Solar Heat Gain Coefficient

If the number of the solar heat gain coefficient is closer to zero, less solar heat is transmitted into the home.  These windows block heat better, and are better for use in warmer climates.  If the number is closer to one, more solar heat is transmitted into the home.  These windows collect heat and help warm the house.  These windows are best used in colder climates. 


The United States is divided into zones to determine where particular Energy Star qualified windows should be used.  About half of the country is located in the Northern zone.  This part of the country is recommended to use windows with a higher solar heat gain coefficient.  This allows more heat into the house when it is cold out, and reduces energy bills in the winter.  The more solar heat that is allowed in, the less energy will need to be used to heat the house in the colder months.

The North Central and South Central zones vary in their needs, and several other factors come to play in the solar heat gain coefficient they should use when selecting their windows.  These factors include external shading and average air conditioning costs.

A small portion of the United States is located in the Southern zone.  This zone is to use windows with a lower number in order to keep the homes cooler in the warm climate. 

When shopping for new windows, look for the Energy Star label and a solar heat gain coefficient that is appropriate for your home.  You will save a little on your energy bills, and contribute to helping our earth at the same time. To learn more, contact a company like with any questions you have.