Living in southern California, in the past I have only used batt insulation. In the current situation, I am insulating a vaulted ceiling: drywall on the bottom of the rafters (2x8s) and the roof on the top. I wish to get the maximum insulation possible. If I use conventional insulation (batt or rigid), I know I need a ventilation space above the insulation and would probably use a ridge vent with venting at the eave. The fire frowns on eave vents.
An alternative is icynene. I understand it will fill up the rafter bay and does not need to be vented. I am suspicious of this. Also, in an environment of great heat, will the paper under the shingles (faux slate?) cook and prematurely fail? Will the heat damage the icynene?
Anyone know about the do it yourself spray foams for such an application? Also, while we are at it, are there problems with ventilation in the walls after installing insulation?
Thanks for any comments.
Replies
I will answer just to move your post up to the top of the list for others to see, but from what others have said here, foam seems to work and doesn't need ventilation. Don't know about the faux slate shingles--maybe manufacturer's web site or the package they come in would say something?
If this were new construction the ideal thing would probably be a hot roof, with layers of foam over sheathing, and more sheathing over the foam.