Insulation, Radiant and Vapor Barriers - Insulating Windows

I am losing heat(or should say accumulating cold in winter) from around my windows, and was looking into using low density spray foam(or mousse) and am interested in knowing whether this should be done from the outside or the inside.

Wayne F

It all depends on the type of windows you have. However in most cases, insulating is best done from the inside by removing the interior trim. Often you will want to cut out the drywall that is covering the rough opening because it's in the way. (as long as the trim will cover it, it's safe to cut it out) You can do that with a drywall saw, jigsaw, reciprocating saw, etc. Dropcloths and a vacuum will be needed! The best thing to do is spray a bead of foam clear to the exterior of the rough opening, then spray another bead that is closer to the interior of the opening.

For gaps less than 1/2", I prefer Dap Latex Door and Window foam (that has been carefully warmed in an oven). If the gap is larger than 1/2" a polyurethane foam works best- but you have to be very sure that it has low pressure (specifically for doors and windows), and you have to be very careful not to overfill the cavity.

If you are insulating a lot of windows you might invest in one of Great Stuff's professional gun dispensers, which are around $50. Around here I know you can get them at Menards. The cans that go on them are 22 oz and they're a better value, are easier dispensing than the straw cans and so make less of a mess. But like I said, they work best when the cavity is at least 1/2". The Dap cans work really well for tight spaces- even down to 1/8".