Your home’s windows are probably the weakest part of your home’s thermal barrier. Storm windows will improve the efficiency of your existing windows, and can be installed on either the inside or outside. They save energy and money in two ways: by slowing heat movement and by reducing air leakage.
Their energy savings, and your return on investment, depend largely upon the quality of the primary window they will cover. If you already have high quality double-pane windows, storm windows won’t reduce your utility costs much. But, if you have leaky single-pane windows, adding storm windows may make a noticeable difference in utility costs and comfort.
If you live in a northern climate, storm windows will save substantial energy and improve comfort noticeably. They also increase the temperature of your windows and reduce window condensation and moisture damage during cold weather. In hot climates, storm windows won’t have such a dramatic effect on energy cost and comfort. Unless you order them with special reflective glass, they won’t reduce solar heat gain, which is the major air-conditioning load.
In any climate, storm windows, installed on the outside of your home, will help protect your primary windows from damage caused by rain or snow melt. This is most important if you have wooden primary windows. If your windows are aluminum or vinyl, this exterior protection isn’t as important. Interior storms that clip onto your existing windows may be a good choice in this case. Interior storms are usually more airtight, cheaper, and easier to install.
The cost of new storm windows is usually about one-quarter the cost of new primary windows. But new primary windows will always be more convenient to operate and more aesthetically pleasing than even the best storm window. Compare the cost of storm windows with the cost of window replacement before deciding which option is best for you.
For more information on storm windows seeThe Homeowners Handbook to Energy Efficiency.