Installing New Storm Windows

Intro

A high-quality storm window can seal out cold air better than a replacement window for a much lower cost. You can install one yourself in far less time than it takes to install a window.

Unfortunately many storm windows are poorly made, with flimsy corners, weatherstripping that doesn't seal well to begin with and soon gets worse, and small parts that easily break. You'll save money in the long run and prevent hassles if you spend more to buy a quality storm.

A standard storm for a double-hung window is triple-track, meaning it holds two glass sashes and one screen, each of which travels on a separate track. If you like to keep the window open in the summer, you can buy a second screen sash to replace the top glass sash.

A storm window is only as good as its installation. The unit must be installed square or the sashes will not slide smoothly. And it must be tightly sealed against the house with caulking and screws.

Prestart Checklist

Time
Once the unit is purchased, about an hour to install a storm window

Tools
Framing square, tape measure, drill, paint scraper, caulk gun, hammer, screwdriver, tin snips

Skills
Measuring and checking for square, applying caulk, driving screws

Prep
Choose a quality storm window and order one to fit your opening. Use a stable ladder and protect any plantings below.

Materials
Caulk, wood or decking screws (or the screws that come with the storm window)

Get free estimates from local handymen.

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Choosing a quality storm

A high-quality storm window has a frame with tracks that the sashes fit into, much like a double-hung window. (The cheaper type has pins at the sash corners that fit into channels.) The sashes and screen should slide smoothly. The sashes should lock open securely and be easy to release for closing. The window should feel solid when you grab it at either end and try to twist. (A cheap storm flexes easily.) The tie bar in the middle and the corner joints should feel solid. The weatherstripping should have a substantial pile that is easy to replace in the future. (A cheap storm has thin, fuzzy weatherstripping that compresses easily and is difficult to replace.)

Step 1

Remove the old storm window or any other hardware that can get in the way of the new storm. To check the window opening for square, first hold a framing square at the corners, then measure the diagonals. If the opening is out of square by more than 3/8 inch, you might be able to adjust the molding to make it square. Otherwise order a storm window that will fit into a smaller opening with square corners.

Measure the horizontal dimension at the top, middle, and bottom of the window, and use the smallest measurement. Also measure the verticals at three points.

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How to Measure

The storm window is attached to the house by driving screws through a flange. Often you will fasten the flange directly to the casing. When you measure for this type, check that the flange only, not the sash as well, overlaps onto the trim. If your opening has an inner stop that is at least 1/2 inch thick, you can fasten the storm to it instead of the trim.

Step 2

Scrape away built-up paint as needed. If you expect to paint in the next few years, consider doing it now; painting will be a bit more difficult after the storm is installed.

Get free estimates from local handymen.

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What If... You want an inside storm window?

If it is not feasible to install an exterior storm window or if it will spoil the appearance of the window, consider interior storms. A typical unit comes as a kit that you can easily build yourself. The pane is usually made of acrylic, and the frame attaches to interior stops using self-stick tape.

Step 3

Set the storm in place in the opening. Have a helper inside check that it is square and that the sashes slide smoothly.

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Step 4

If you are installing inside the casing and the stop on the window is narrower than the flange, you can remove the casing or pry it loose so the flange will be behind it. If that is not feasible, cut the flange as necessary, using tin snips.

Get free estimates from local handymen.

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Step 5

If the flange does not already have screw holes, drill them now. Position them every 8 inches or so.

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Step 6

Apply a generous bead of butyl, silicone, or other door and window caulk wherever the window's flange will rest along the sides and top; do not caulk the sill.

Get free estimates from local handymen.

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Step 7

Tilt the storm into the opening. Take care to position it correctly the first time so you don't smear the caulk. Press the flanges into the caulk and ensure that the unit is sealed all along the sides and the top.

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Test window alignment with framing square

Step 8

Drive a screw into the center of the top flange and partially drive a screw into the side flanges near the bottom. Test the window's operation. If the sashes are misaligned to the frame, remove the lower screws and adjust the window as needed.

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Step 9

Once you are certain the window is square, drive the rest of the screws. Scrape away caulk that squeezes out under the flange.

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Step 10

A portion of the flange or a flange extender usually must be modified for a tight fit against the sill. Usually you can do this simply by tapping with a hammer and screwdriver to bend the flange.

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Step 11

Angle-drive screws to attach the flange or flange extender to the sill on each side.

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Step 12

Apply a thick bead of caulk along the flange at the sill. Recaulk other areas as needed. Do not seal the weep holes, which are needed to prevent condensation.

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