It’s a familiar story. Your old windows leak copious amounts of air, which makes for chilly drafts in the winter and higher cooling costs in the summer. Leaky windows may even be hurting your house by allowing windblown rain to seep into the structure.
Time for new windows? Not necessarily. High-quality storm windows may be all you need to banish leaks, at a fraction of the cost of replacement windows. “A good storm stops air infiltration about as well as most replacement windows, and the upfront costs are much lower,” says This Old House general contractor Tom Silva. “It’s like putting money in your pocket.”
The typical aluminum “triple-track” — so called because it holds two glass sashes and one screen that slide up and down on separate tracks — won’t win any beauty contests, but it can also play an important preservation role by protecting valued old-house windows from the elements.
On the following pages, Tom demonstrates how to measure for and install an aluminum exterior storm over a double-hung window. (Outward-swinging casement or awning windows require interior storms.) Tom has the window up in less than 10 minutes, but while installation is simple, he says, there are still ways to mess it up. “The most common mistake people make is to caulk the storm’s bottom edge, along the windowsill,” he says. That can trap water that leaks in or condenses on the inside of the glass. “You want to give water a chance to escape before it causes any damage.”
Ensuring a Proper Fit
First, determine how your storm window will be mounted to the main window. If your main window has a “Western” casing, the storm will be attached to a recessed 5/8-inch blind stop within the window opening. “Eastern” casings have no such stop; the storm overlaps and attaches to the casing itself.
Next, measure the windows. Find the horizontal distances between the inside edges of the window casing at the top, middle, and bottom of the window. Then measure the vertical distance from the bottom outside edge of the head casing to the sill. Finally, check window sash height. If the top sash is shorter than the bottom ones (called an oriel window), order your storm sash to match those dimensions and preserve the window’s original appearance. Finding the Right Size
For an Eastern-style casing, the storm window should be at least 1 ¼ inches wider than the opening’s maximum width. The height should be about 5/8 inch taller than the window opening, but no less than ½ inch.
For a Western-style casing, the storm’s width and height can be up to ¼ inch less than the opening’s smallest measurements. A smaller gap than ¼ inch is acceptable, as long as the storm’s fins do not hit the inside edges of the casing.
What to Look For in a Storm Window
When Tom Silva shops for storms, he looks for the following indicators of quality because they translate into better performance, greater strength, and long-term durability. “Sure, you can buy a cheap storm window, but why bother?” he asks. “You just end up paying for it later when it leaks, rattles, or doesn’t operate smoothly.” The window he’s shown installing here costs about $160.
Where to Find It
Harvey Industries, Inc.