Open-cell foam sprayed on the underside of roof sheathing
I was at a house recently. It was a 2-story built around 1920, so it probably had 2 x 4 rafters. In speaking with the owner he said that he open-cell foam sprayed on the under side of the roof deck. I asked if I could see it.
What I found was that the open-cell foam was left uncovered, with no fire barrier. I do not know how thick it was, but doubt it was much over 4.inches. I am in Nebraska to give you an idea of the climate.
He was told open-cell was used as it will allow any roof leaks to show up.
The electrical has been replaced — expect for knob-and-tube that goes to the attic light. The wiring was mostly under the open-cell.
The existing insulation was left in place. It was vermiculite with fiberglass batts over some but not all. It was a walk-up attic with planks in the middle.
I advised the owner that the foam needs a fire/flame barrier and that the foam should not have been installed over knob-and-tube. I also told them that the vermiculite may contain asbestos and to have it tested before disturbing it.
To my questions:
1. What is going to happen to the insulation when the shingles need to be replaced?
2. Should the existing insulation have been left in the attic or should it be removed? If removed, why?
3. What is your opinion on using spray foam on the underside of the roof without providing a more durable and weather resistant roof?
4. How much of a fire hazard is the wiring for a single light?
5. For this house, what is your recommendation for bringing the attic into the conditioned space? Or would you have left the thermal and air barrier at the attic floor?
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