Thin insulators, no recessing of window & door frames?
Hi. I live in a 2x4 frame house with fiberglass-bat insulation (built 1978). We're in plant-zone 6 and get a coldish winter, hot mid-summer (but not as cold a winter as much of the rest of Canada). About a year ago, I read about a highly reflective paint layer that has been developed - remove your exterior siding, paint it on the inside of the siding, replace, and you supposedly have a significantly improved R value, due to reflected heat.
I don't know how true this is, about this sort of product. But it's made me wonder if there IS some thin (possibly quarter-inch) material that can be installed under siding that can significantly increase R value, without resulting in recessed window and door frames. By the way my house was originally built with black-building paper over plywood sheathing behind the siding, and with a plastic-sheet vapor barrier on the interior behind the drywall or wood panelling.
What do you know of about thin insulating products? And, if such products exist, are there down sides to using them in a house like mine? And how costly are these materials? Thanks.