will any type of plastic work for insulating windows?
I would suggest the type that are like storm windows. They are double layers and create dead air spaces that stop the heat flow -- not much of an R value, but better than thin plastic sheeting. R= 1 (for the really cold days, the best insulation for windows is to cut a 1 inch thick foil faced styrofoam sheet - cut it to size so that it pressure fits inside your window framing. = R = 6.5
Yes, as long as you can seal the edges well enough so no air can get through to the space between the window and the plastic. That air space is what does the insulating, so if air can pass through it there's not a lot of point in using the plastic, unless you have old windows that are extremely drafty. In that case, anything that slows down the escape of heat will help to some degree.
Yes, but some are better than others. Anything that is strong enough that it won't tear will stop air from coming in. The plastic has no insulating value, or almost none. The value is that it traps air and thus resists heat flow. I prefer a crystal clear plastic because it looks better.
