Do you feel cold standing next to your windows? With easy to make interior storm windows, you can feel warmer while saving money on your fuel bills. These storms will increase the R-value of your windows by around 2.3, however they will reduce the solar heat gain by about 15%. For most windows in Maine, this is a good trade-off. Not only do this save energy and therefore money, they also increase comfort and reduce outside noise.
|1 x 2 board @ $ 0.40 per linear foot||Screwdriver|
|heat shrink film @ $0.09 per square foot||Sharp knife|
|½ double sided tape @ $0.02 per linear foot||Sandpaper|
|2.6 mil 2 clear packing tape @ $0.02 per linear foot||Square|
|3 drywall screws @ $0.05 each (8 needed per window)||Saw|
|½ x ½ foam weatherstrip @ $0.06 per linear foot||1/8" Drill|
Measure: The storm windows should be put as close as possible to the glass of your windows (½ is best). However it should be placed such that it contacts the frame all the way around, if necessary it can be placed on the window trim, and held on with clips. Having determined where you will put the storm measure carefully the width and height of each window. Measure in at least two places, and average the readings, then subtract the thickness of your weatherstrip ½ (which will compress the 2 thicknesses by half giving a nice seal). The short side will need to be shorter by the width of two pieces to make the butt joint.
Frame: 1 x 2s can be made by ripping down a 1 x 4. The wood does not need to be high quality, #3 pine works fine. But pre-primed is easy for frames which will be painted (or white). And clear pine looks great unpainted. The corner is made with a butt joint held with two 3 drywall screws in pre-drilled holes at each corner. The long sides should be ½" shorter than the window opening (for the width of a two compressed weather strips). The short sides should be shorter than the window opening by ½ and two widths of the frame wood (for the butt joint). Screw from the long side into the short side (as shown). Sand the frame smooth and knock the edges off slightly. Now is the time to paint, finish, if desired. Also be sure to label which window the frame goes into, on the top outside surface.
Films: This works best if done in a clean environment. Put the double sided tape around the edge of the frame (on the face). Leave the paper on for now. Cut the film to cover the frame plus a little for slop. Start at one end, and remove the tape, and carefully stretch the film and place it over the exposed tape. Press it down with the back of your fingernail. Fold back a bit of the tape down both sides , and work your way down the frame. Finish with the last piece of tape.
Once it is firmly in place, trim the excess film at the outer edge. Then shrink the film using a hair dryer (a heat gun can be used if you are very careful). Stay 6 to 8 inches away from the film until you see how it goes. Slower is better than melting a hole in the film. It should end up drum tight with no wrinkles. Looking at it obliquely to the light will show any remaining wrinkles. Starting in each corner seems to mimimize any wrinkles. Repeat with the other face (or install film on both sides, and then shrink). Try to make sure that the inside faces of the film are clean, as once assembled, the inside can't be cleaned.
Tape: The 2 tape is used to cover the film edge and the outer edge of the wood frame. Be sure to leave a bit to wrap around the corner. One piece for each side (4 pieces all together) works best for me. Use a short piece of tape to create one or two tabs to make it possible to remove the storm. Start on the back side, about 10" up from the bottom, wrap the tape outwards across the face and then the edge. Then extend out away from the window about 1.5" and fold back on itself. Make sure that the edges of the tape are lined up; make a crease at the fold. Finally, continue onto the front face.
Weatherstrip: The weatherstrip (½ wide, ½ thick) is placed on the outer edge of the frame. For each piece, start at the outer edge of the previous piece, ensuring an nice square corner. If the window is to be installed against the window trim, it should be placed on the back face, of course.
Use: The storms should be swapped out with your bug screens when you are starting up your heating system. (Removing the screens will save you about 1% to 3% of your fuel bill by itself). Store them for the summer where you store your screens. Be sure to lock the windows before installing the storm; windows do not seal properly unless they are locked. Arrangements should be made to ensure easy removal in any window which is an emergency egress.
Savings: Given the prices above (which are for small quantities) a typical 3 by 4 foot window would cost, $9.59 and probably require less than an hour to build. The savings depend on what kind of windows you currently have and what kind of fuel you are using. For single pane windows, the savings would $202 in electricity, $135 in oil, or $69 in wood. For double pane (soft coat) lo-e windows, the savings would be $68 in electricity, $45 in oil, or $23 in wood. All of which would give a payback at less than one year (at today's prices, imagine prices in ten years). Theses savings are tax free, repeat every year, and increase along with fuel prices. Triple pane, or south facing hard coat lo-e double pane windows are the only windows that might not benefit from this approach.
The film is susceptible to tearing if it is poked with anything sharp, but with proper care there is no reason these couldn't last at least ten years. Over the past 2 years, since these made their debut at 2008's expo, over 5 thousand of them have been made by Mainers and for Mainers. I and, the Midcoast Green Collaborative are proud to have been instrumental in helping Mainers through this past winter.
Variations: Over the years, many changes have been made to my original design, by Guy Marsdaen, Charlie Wing, Habitat for Humanity, and others. Here are my opinions of the differences.