How to Make Your Own Magnetic Interior Storm Windows

If, after reading about the comforts that our new interior storm windows brought, you’re interested in making your own magnetic interior storm windows, then here’s some information for you:

Materials to Buy:

  • Magnetic frames for storm windows – We chose to go with Climate Seal because they used a bellows system, which allows the storm window to flex in and out with changing temperatures. These were available in a few colors (and I believe they now offer a woodgrain look), but we went with white since our windows were all painted white to begin with.
  • Permanent steel framing pieces – These give the magnets something to stick to, and have a couple of options: (1) steel angle, which is screwed into the window jamb, or (2) flat steel which adheres to the window stop. We chose mostly steel angle because we prefer mechanical attachment to adhesives, but we did get the flat steel for a couple of our windows that weren’t as roomy. In retrospect, we would prefer a flat steel which screwed into the window stop (we just don’t dig on adhesives… I think we’re traumatized by sticky residue). Whether you go with steel angle or flat strips of steel, this metal will be visible whenever you remove the storm windows. We chose a white finish, to match our trim, and they blend in nicely in the summertime when we take the windows down. (The salesman at Climate Seal spent a lot of time after-hours on the phone helping Aaron determine the best type of steel for each window. Talk to these people. They can make the waters a little less murky.)
  • Foam tape – This will go between the steel angle pieces and your window jamb. It makes the storm windows air-tight. Not necessary if you go with the flat steel.
  • Window surface (glass, plastic, etc.) – We had considered using glass, but at 3′ wide by 6′ tall the windows would have been too heavy to lift easily.  Plus, we frequently have airborne dog toys flying around the house, and glass is a little too fragile for comfort. We started considering our options with plastics. Among the plastics, polycarbonate (Lexan) and acrylic (Plexiglas) are the most common. Plastics offer decent optical clarity (comparable to glass) are less fragile than glass, and much more lightweight than glass. Unfortunately, plastic will yellow a bit with age, and it scratches easily. Polycarbonate (Lexan) is more shatter-resistant and scratch-resistant than acrylic (Plexiglas), but it is also more expensive. We ended up choosing acrylic because the cost savings was significant.
  • Non-abrasive window cleaner – Especially important for avoiding scratches if you’ve chosen a plastic window surface, as the window will be covered in clinging particles of sawdust thanks to static by the time you’re finished. Make sure to buy a cleaner specifically formulated for plastics.

Other Materials You Might Need:

  • Workbench – the 4’x8′ pallet they ship the acrylic on converts nicely into a workbench that is the perfect size for assembling the windows
  • Circular saw and straight edge
  • New blade for your circular saw. Depending on your chosen material, you’ll need a saw blade with a certain number of teeth per inch. Aaron found that having slightly fewer teeth than suggested worked well (of the two standard wood-cutting circular saw blades you can buy, use the finer-toothed one). Too many teeth per inch will melt your plastic, rather than cut it, and you’ll have a wavy melted edge instead of a nice straight cut edge. Too few teeth and your plastic will shatter.
  • Miter saw or miter box
  • Rubber mallet
  • Tape measure
  • Autoglass/windshield suction cups – handy for picking up the windows


  1. Measure your windows in 6 dimensions (left and right vertical, top and bottom horizontal, both diagonals), and use these measurements to order your plastic.
  2. Painstakingly mark an acrylic sheet for cutting to slightly out-of-square dimensions. Get out the geometry book for this one, kids. (Note: rather than use the diagonals, which were difficult to measure accurately, we held our plastic sheets, which we assumed to be square, up to the windows and measured the gaps. A 3/8″ gap on the bottom right meant the bottom left side needed to come up 3/8″. This gets confusing; remember the old adage measure twice, cut once. Better yet, measure 3 or 4 times and draw a picture before you cut.
    A Note on Cutting: Adjust your saw blade to the correct height beforehand. You want your saw blade height to be just a tiny bit more than the thickness of the plastic. If the blade height is too large, it can cause the plastic to shatter.
  3. Once your window is cut, sand all newly cut edges, and sand them well. This will make step 5 easier.
  4. Remeasure the sides of your cut plastic and add 3/16″ to each dimension. These will be the outer dimensions of your magnetic frames. Cut your magnetic frames to the appropriate length for each side (length of plastic side + 3/16″), and then cut in at 45 degrees so the inner dimension is smaller than the outer dimension.
  5. Press the frame onto the plastic starting at one end. The outer edge of the frame should extend approximately 3/32″ past the plastic. Use a rubber mallet to firmly press the rest of the frame into place. This is the tricky part because the frames don’t slide once they’re on the window surface. If you get to the other end and find that the frame is not centered on the plastic (or worse, is too long and needs to be cut shorter), you’ll have to pry the whole side off and start again. This will probably take several tries the first time you do it, but by the time you get to your seventh window, you’ll have a better eye for lining up the frames from the start.
  6. Once all four frames sides are in place, you have a completed window! Cut your steel frames to the dimensions of your windows, apply the foam tape and screw them in (or adhere them), and you can fit your magnetic interior storm windows into your actual windows. Before long, you’ll be enjoying the benefits of heat retention and noise reduction! Good luck!
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