Can polyiso be added to interior finished walls?
We are looking at a house to buy that was built in 2003, but has insufficient (R13) insulation in the walls. The windows don't look so great either. The interior is finished in drywall. Can polyiso be glued and/or nailed to the interior walls and then paneled over? The paneling would be glued and nailed too. Would the polyiso provide enough of a backing for the paneling? Would there be a condensation problem in the walls? It appears that house wrap was used under the Hardiboard siding (no passage for rain there though). There may be cellulose in the walls, but I'm unsure of that. What is the best way to seal the T&G—bead of caulk in the groove? Glue at the back of the tongue? What glue is used on polyiso?—I understand commonly used glues dissolve it.
I am thinking of 1/2 polyiso and 3/4 paneling, or 1" polyiso and those 3/8" panels that come in overpriced kits, but would provide a lot more R value.
There are 6 fixed thermopane windows on the north wall in the living room. They look like cheap vinyl, so I thought of getting more thermopane glass and installing them on the inside of the window openings. This would substantially increase R value by having one sealed unit and an airspace between the 2 thermopane units. With the paneling, I can make this look good and hide the vinyl around the original windows.
This house has a lot going for it but some things have been done badly and I can fix them fairly easily (famous last words remembered after 5 or 10 years fixing things). The 700 sq. ft. shop in a walkout basement certainly would make me happy and provide a place where I can work on things for the house and the big kitchen makes my wife happy.
Are these crazy ideas or am I onto something?