Insulating Room With ICF Walls and Open-Web Truss Floors
This is in Nashville TN, in a 30×30 garage with a full size bonus over top unconditioned garage. The walls are ICF to the eaves, the bonus subfloor and ICF wall intersection was sprayed 3″ closed cell foam. The trusses are 24″ deep, and the entire garage is drywalled.
The insulation contractor believed that spray foam solves every problem, and decided we didn’t need other insulation before the drywall was installed in the garage (required by code over trusses and ICF foam).
The bonus room is noticeably cooler in the winter and warmer in the summer. The rest of the house (also ICF) is pretty thermally amazing, but the 900sf bonus room is a giant temperature differential that sucks.
How do I beef up the insulation for the bonus room now that we’re in the house? (Thanks for not commenting on how steel beams, LVL-and-joists, or other after-the-fact design change would make my life better. That ship has sailed.)
Blown in fiberglass (drill holes, let it settle on the drywall ceiling)? Blown cellulose? Rigid board on the exposed side of the garage ceiling? More foam? Cut an access scuttle and try to roll batts?
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