Insulation retrofit: Icynene, cellulose, fiberglass?
Does anyone have experience with retrofitting an older house with Icynene in the walls or on the attic floor?
And, does anyone know whether corrosion or dust are still issues with cellulose?
My house is 75 years old, has no insulation in the walls, which are plaster-and-lathe. About a third of the attic floor has fiberglass batts, a third (the middle) is covered with wood flooring with no insulation below, and a third is uninsulated open rafters. I'm getting new energy-efficient windows, and Craneboard backed vinyl siding to cover my 3/4-inch-thick, 8-inch wood clapboard. (Clapboard has layers of peeling and previously peeled paint)
Obviously, I need attic insulation, and, if I'm going to get insulation pumped into walls, time would be now before new siding goes up. I'm leaning toward Icynene for the walls. Was quoted $3,200 for that. Was quoted $4,400 for dense-packed cellulose in walls and cellulose in attic.
I'm leery of cellulose because I've read that cellulose treated with sulfates could be corrosive. National Parks Service Restoration Brief 3, written in '79, warns against using sulfate-treated cellulose -- That may be out of date, but I haven't been able to find any reliable source that flat-out says this is no longer a problem. On the other hand, I hear cellulose treated only with borates is very dusty, and it doesn't seem to be available from installers here.
I don't know if Icynene can be used on an attic floor, or if it can, whether it would provide sufficient insulation. (My area calls for R49 in attic.) If 4 inches of Icynene were pumped in (I understand it would have to be covered), that would be about R16, although I'm told its superior air-blocking might make it seem like more.
Also, the foam's air-sealing quality seems desirable, or would that make my house too air-tight and unable to breathe? I guess there are plenty of air leaks from my old house to attic, but I doubt I'll find either the leaks or a contractor willing to search diligently to repair them, so Icynene would seem like an easy way to block them.
Oh, also, my central air conditioning unit and its ducts are in the attic. And, I've been warned by my roofer not to go the route of sealing off the attic and putting foam on the roof line.
Thanks for any experience or tips.