I live in the panhandle of Texas, where we can have several 100+ days in the summer and temps below 10 in the winter.
My attic currently has blown-in fiberglass insulation about 5-6 inches deep. The attic is ventilated with soffit vents and an attic fan that operates when the attic temp exceeds 90 degrees.
I would like to remove the fiberglass insulation and replace it with a spray-in foam like Icynene (icynene.com). From what I've seen online, it appears that the foam products are usually applied in the rafters of the roof.
So, my first question is this. Is it ok to intall the spray-in foam in the ceiling joists and if so, does any of the wiring or ductwork or electrical boxes have to be protected from the foam? I would prefer this type of application to hopefully eliminate a bad dust problem that appears to originate in the attic.
If a celing application is not recommended and the foam is instead applied in the rafters of the roof, would I then need to remove the attic fan and plug the soffit vents so that the attic would be a closed environment? Would the fiberglass insulation in the ceiling joists need to be removed – what is the best/easiest way to remove it?
Matt, this is the exact insulation project I completed last spring in my own home, and these are all great questions. The best place to apply Icynene is to the roof rafters. Icynene is a great product. I'm thrilled with my utility bills since using it, which are half what they were before. To apply it, spray it into the rafters. The Icynene will probably surround the rafters, so you won't be able to see them once you're done. You're essentially converting your attic from vented to non-vented, so yes, you will be sealing the vents and removing the attic fan. As far as mechanicals are concerned, all I did was secure loose wires and ducts and spray the foam around them without harm. Finally, as for the fiberglass insulation in the ceiling joists, you can leave them in place. Doing so will neither hurt nor harm them, so I just left mine in place for the little bit of extra insulation they provide.