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What to Consider When Purchasing Energy-Efficient Windows

If your heating and cooling costs are higher than you'd like, you may want to purchase new windows that are more energy efficient. Installing energy-efficient storm windows can reduce heating and cooling bills anywhere from 12 to 33 percent per year, especially if your windows are damaged or more than 20 years old. There are a few features to look for if you want the most energy-efficient windows available.

Type of Window 

As you may expect, fixed windows are among the most energy efficient, but most people would prefer other types of windows since these can't be opened. Sliding windows and double- or single-hung windows tend to leak more air than casement, hopper or awning windows — making them less energy efficient. 

Frame Type

Aluminum frames may be inexpensive, but they conduct heat, which means they are not the best choice for energy efficiency, even if they have a thermal break. Instead, choose wood or insulated vinyl frames.
Fiberglass windows need more maintenance, but if you can find insulated versions, they can be very energy efficient. The air leakage score of the window should be 0.3 or less and the R-value should be somewhere between 2 and 5.


To help keep homes cool in hotter climates, look for Low-E coatings on the outside of the glass. These coatings reflect 40 to 70 percent of the heat away from the window, helping to keep the home cooler. The best coatings allow visible light to enter the home but not heat.

Look for a solar heat gain coefficient (SHGC) that is 0.25 or less. Those who want to block some of the light as well to protect belongings from fading should also look for a low visible transmittance rate (VT).

Number of Panes and Gas Filling

Having multiple panes of glass helps increase the energy efficiency of a window. While just having air in the space between the panes helps, having the space filled with a heat-stopping gas, like argon or krypton, will help insulate the home even more.

There's some debate on whether the additional cost is worth it to have three panes installed instead of two. However, the increase in energy savings isn't as significant as going from one pane to two panes.


Another measurement typically mentioned on energy-efficient windows is the U-Factor. This number measures how well the window conducts heat. Those living in the south-central part of the country should aim for a U-Factor that is 0.3 or lower. Those living in the south should look for windows with a U-Factor of 0.4 or lower.

Other Window Tips

Using white window treatments may help improve the energy efficiency of the windows. Also, installing awnings over windows on the south and west sides of the home will help keep heat from entering.

It's also a good idea to have the curtains closed on these windows during the day. A tree planted in just the right location can also be a useful way to block some of the light and heat from entering a window.

Energy Star Standards

One easy way to quickly narrow down the options is to look for Energy Star ratings. These windows will meet the minimum standards, but not all Energy Star windows are the same.  Compare them carefully before making a choice. A window that meets the R-5 standard will be more energy efficient.

Installation Considerations

Because of the complexity of many of these windows, it's best to have them installed by a professional. After installation, you shouldn't feel any air coming in around the window frame, and the window should open and close easily. When the window is open, look to ensure that it is properly aligned and the gap is the same on both sides.

Contact the professionals at Window Tech, Inc. for help choosing the best windows for your home.