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Interior Storm Windows - Save $700 + a Year

by Joy Kieffer


That’s how much I saved just from January until the end of the heating season the first year I made these! For an investment of a little over $100, that’s a pretty good profit. These were prices from about ten years ago, and the storm windows have lasted that long.

The idea of interior storm windows isn’t new. There are all sorts out there, but they are either pricey, or they require adhering or screwing something to the painted surface. Being a cheapskate, I couldn't see spending $200 + per window, and I certainly didn't want the paint to pull up when I wanted to remove these in the spring. (I actually leave most of them up year-round because they work just as well to keep the heat out in summer.) 


Supplies are readily available in almost any home center or hardware store. Go to the section of the store where they have supplies for screen windows and repair.


You will need:

  • Aluminum framing for screen windows

  • Screen spline which is pressed into the channels in the frames. This comes in rolls.

  • Plastic corner inserts (four per window)

  • Roller tool. Notice in the image below that I marked one of the rollers with V shapes so I didn't use the wrong end. You will be using the inverted U shape to press the spline into the grooves.

  • Plastic (clear unless you want frosted) that comes in rolls. It needs to be flexible enough to go into the grooves in the frame and thick enough to hold its shape while working with it. The thicker it is, the more it insulates, and of course the more expensive it is.

  • A saw with metal blade to cut through the aluminum

  • Poster putty


When you measure your windows, you will be measuring INSIDE the wall set-back for the window. If the windows are mounted flush with the wall, measure the area of glass, or the inside of the casement if there is space. You will be adhering the interior storm windows using simple poster putty. A ball about 1/2” in diameter stuck behind all four corners is enough.


Before you measure and cut the frame pieces, remember to take into account the distance of the corner pieces.  Windows more than 4-1/2 feet in any direction will probably need an additional frame section added for bracing. Since my casement windows are 3’ wide x 5’ high, I simply set the extra frame piece inside the frame without attaching it. Tension holds it in place.


Cut the plastic at least 1-1/2 inches larger all around than the frame. Lay lay the assembled frame on the floor or work surface with the groove sides up, and then lay the plastic on top. Cut the rubber strips a bit longer than needed. Start the long sides first, pressing the strips into the frame at the middle of each side for about a foot. Then start the shorter sides. Keep working your way to the outside corners, alternately, long to short. Cut off the remaining rubber. Trim the plastic close to the rubber.


Install the storm windows using a ball of poster putty behind each corner. Press the window frame corner to secure.


Once the windows are installed, compare the temperature of the plastic to the surrounding wall and other windows!

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