Foam Board Window Insulation

Windows, regardless their independent insulating qualities, are never very good. Even with the best residential gas-filled, double glazed windows you can buy, you can get an R-value of maybe 3 or 4. Add 1 if you use insulated curtains. Blue or pink extruded polystyrene (XPS) foam board has an R-Value of roughly 5 per inch, if I remember correctly. By cutting foam board to fit in your windows, you can increase your window insulation by however thick you make your foam.

Foam Insulation Shutters:

1. Neatly cut sheets of blue or pink foam board insulation just slightly smaller than your window opening and remove the plastic film. Cut a piece of burlap several inches larger than the dimensions of the foam board. Fold burlap in half with the fold in the middle of the foam board and the other ends over the short edge of the foam board. Like putting in an auto headliner. Use the kind of spray adhesive that is used for foam and fabrics. Apply adhesive to the width of the foam board starting at the fold in the middle and working about a foot  down the foam, and up the cloth. Trim burlap. Burlap can be primed and painted, if you like. Make a hole an inch or so away from each corner and put in twine loops so you can remove tight shades from the window.
2. Bigger shades - Cut the foam board bigger than the window if you don't mind putting hooks on your wall or window frame. Since the foam/burlap is not solid, you can just punch some loops through with a large needle and small twine wherever you need them to fit on the hooks. This will prevent air leaks if you get hooks small enough to hold the foam board flat against the wall or window frame.
3. Have not tried - Make much more elaborate versions of this project with lightweight wooden frames. Either make two shutters per windows like old-school shutters, or make a top and bottom half and hinge together. Cover fronts and backs with 1/8" or 1/4" plywood. These frames will be heavy and solid enough to damage paint and drywall - best used in applications where they can by permanently fixed to the window frame with hinges.
4. Have not tried - Glue composite beadboard panels to the front and back of the foam board with the beadboard sides showing (Liquid Nails Projects and Foamboard Adhesive.) Cut panels with circular saw to fit in the window, leaving a little space around the )edges to accommodate a trim piece (and a little extra to get the board in and out of the window. Buy a 1/4" flat trim piece the width of all three of your assembled panels (Ex: 1/8" beadboard + 1/8" beadboard + 1" foam = 1 1/4" trim width.) Apply the strips to the edges of the panels with something like Liquid Nails Projects and Foamboard Adhesive.
5. Make cloth covers for them, if you'd rather sew. The covers can be taken off and washed, and the foam can be replaced if it becomes damaged.
6. You can also just put the raw foam board in the window with the non-printed side in and close you curtains. Hey, I've done it. Works super awesome.
7. I used some Zinsser Gardz water-based multi-surface prep stuff that made it a little easier to work with. Then I used Modpodge to decoupage small pieces of thin kraft paper to it. Needed to be weighed down to stop bowing. You can also prime the foam with water based primer to make it paintable and for adhering things to the board - but wet product applications will try to bow. Only use water based acrylics and latex paints. I read that shellacing first will stop the board from bowing.
• Things I've tried that do not work or read are bad:
• Large piece of paper
• Pre-pasted wallpaper. I haven't tried regular wallpaper paste
• Elmer's glue
• Polyurethanes other than water based or shellacs
• Most spray adhesives - they eat the foam

Here's How to Use Foam Shutters.