Can I spray urethane foam insulation in cavities that already have insulation in them?
I have done this. It makes a difference in heating the house. I would do it again. Later when I tore into the wall for a plumbing fix, I found the Foam had compressed the blown fiberglass insulation towards the floor somewhat, and where it mixed with the insulation it dried in irregular shapes. It didn’t appear to seal the leaks at the bottom of the framing because the blown insulation prevented the foam from getting that far down the wall. It did seal the leaks at the top of the wall, around windows, doors and other openings. Old houses are a B**** to modernize.
