Make Removable Interior Storm Windows

Wood trim and some plastic sheeting are all you need to assemble your own interior storm windows.

| October/November 2010

interior storm windows

These interior storm windows are sure to keep the cold out this winter.  


Tired of your single-pane and leaky windows, but can’t afford to replace them? Here’s an easy way to dramatically improve the performance of your windows and reduce damaging condensation without spending much money: Make removable interior storm windows using wood casing, window film, and foam tape.

First, acquire some wood-trim molding. Contractors often throw out scraps of this material. All trim should be finished before cutting.

Determine whether you want the interior storm window to fit inside the existing window casing or on top of it. In general, it’s easier to friction-fit the interior storm window inside the existing window frame. To do this, measure the inside of the window frame horizontally and vertically and subtract a quarter inch from each dimension.

Cut the wood to length with 45-degree angles at each end, with the thick edge of the trim to the outside. If using square stock, you can use a rabbit joint (also called a lap joint) at the ends. Lay the pieces out and make sure the frame is square and the proper size. I like to use some nails tapped into a workbench at the outside edge of the frame to hold it in place and keep it square.

Cut a slot in the pointed end of the trim, deep enough to make the spline work, but not so deep you cut through the finished face of the inside corner of the frame. It’s important that this spline cut be made in the same relative location on all of the trim pieces so each corner pair matches. Cut the spline slots the width of your spline material (thin plywood that is the thickness of your saw blade works well for this).

Put the frame pieces between the nails again and glue the splines in place. Trim the spline and clean up the glue. Lightly sand all the rough edges of the trim, then “dry fit” the frame into the window opening. Next, put double-stick tape on the outside edges of the trim. Install the film as recommended by the manufacturer and shrink the film. (You can find interior storm window film at home improvement stores.)

9/18/2013 6:25:16 AM

Just wanted to let folks know that these interior storms really do work, we've had ours for well over a year now. Gotta be honest though, we bought ours from a company up in Wisconsin. I think it's a company called Energy Wise Mfg. A few reasons I bought them rather than try to build them, theirs are built as double glazed (which is fantastic), I didn't have the time or materials to build my own, and their price was very very reasonable, I think a little over $60 average each for our 17 windows. We left them in all summer because we knew they'd cut down on the A/C costs too. My wife especially likes them because they keep dust and dirt out and reduce noise from the outside. Joe, the burbs of Chicagoland

susan laun
1/15/2013 9:11:03 PM

This may be a stupid question, but how do you get these windows to stay in? I have an old house with VERY drafty windows, and I'm afraid the wind blowing against the new storm window would just pop it out of the hole. (When I use the taped-in plastic sheets, it pushes that in and eventually pulls the tape off.) Any helpful hints are welcome!

james reynolds
10/19/2011 8:23:48 PM

AWESOME IDEA!!! and what is even better, it's easy!!

12/1/2010 8:40:57 AM

Jo: Brilliant idea on the attachment of cloth for removal. I have recently made storm windows for all of the windows in my home using the 1x1 and sometimes 1x2's. With mine, I put a sheet of plastic on EACH side, turning them into a double paned storm window which was real easy to do. Additionally, I used a bracer bar that ran up the middle of each of my frames because the plastic would pull in after it had been shrunk. This allowed me to also adhere to the middle bar thus making a smaller loose air area, raising the storm window's efficiency even further. I did use the foam tape as well and the article is spot on about not getting it too thick or putting it in will roll it.

jo _4
10/21/2010 7:31:49 AM

If you are not good at the joints and don't care that it looks like a professional did it, you can use 1 x 1 or 1x2 boards. Cut them to length and drill holes in both ends of the opposite sides and use screws to hold them together. Be sure to paint or stain before you put on the plastic and foam. They are not as pretty or sturdy, but work just a well. Another thing I have found useful is to put a "tab" (small piece of cloth attached to the board on one side) so it is easy to get out without breaking the plastic.

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