Adding spray foam to existing fiberglass filled ceiling
cirino
| Posted in Energy, Heating & Insulation on
I have a client who was interested in removing the drywall and fiberglass insulation from her garage ceiling then having spray foam added to the joist bays and re-drywalling the ceiling. The thinking is to remove any air infultration. We had a spray foam contractor come and look to get an estimate. He says the drywall doesn’t need to be removed. By drilling holes he can add the foam to the bays and it would just compress the fiberglass and fill the bay.
Has anyone heard of this? It just doesn’t sound right to me. Will the foam stick to prevent the air movement? Will the board blow out?
Anyway, any information or opinions will be appreciated. Thanks Ed
Replies
It's a slow curing mix used for renovation.
For this case, since there is already a bunch of insulation there - I would look at Flash & Fill.
Remove the drywall and set the FG insulation to the side NICELY. Spray and inch or two of foam in the bays. Re[place the pink in whatever space is left and recover with drywall.
More insulation and your are SURE to get a good seal from the foam. You are just hoping the foam goes to the right place with the slow cure stuff.
Hmmm...
I would get the name of the specific foam product he wants to use, and get verification from the manufacturer that the product has been tested for that application and will work. My guess is that he's suggesting a "pump-in" foam like Tripolymer 105, which I have seen placed into uninsulated wall cavities through small holes in the siding. It doesn't expand much at all, and has to be put in with great accuracy.
Personally, I would't bother with foam. People need to get over their fear of drywall. Demo the stuff, air seal the floor, and re-rock it. It's not much more of a deal than fixing all those holes and risking a poor-performing foam job. If you want high R values, install some rigid board in the joist bays or across the bottoms of the joists before you rock.