I have a question regarding the spray foam application in this current issue of FHB. Can you use the spray foam in rafter bays? Are there any concerns with moisture? How does is work with a ventilated soffit? Thanks.
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I haven't yet read the article you mentioned, so I'm not sure what products were used.
But in general, spray foams are fine when installed directly to the roof sheathing between the rafters. Icynene and Corbond are two that immediately come to mind. This arrangement requires no venting.
I'm not sure if this approach is universally accepted in all regions of the country, so you'd need to double check with local codes, etc. (I live in Seattle, and it was fine here. )
I'm very happy with the installation at my own home, since the semi-conditioned attic now stays relatively warm in the winter and doesn't cook in the summer. It's a much better place to store stuff, now.
I'm not 100% sure about that. I noticed the FHB article about the old houses they insulated.I find it interesting that Owens corning and Timberline will NOT warranty their shingles unless there's a continuous 1" air space (ie, vented roofing).Also, in many parts of the country (mine included) our local building code will NOT allow for an unvented roof. They will not allow us to use spray foam on the "roof deck".Not saying that it can't be done or that it isn't "good", but you have to be careful with your local codes and roofing product if you want your warranty.
It doesn't work with a ventilated soffit. It's a "hot roof" system that is not ventilated.
I am a fervent believer in roof ventilation for removing moisture, for shedding summer radiant heat, and for keeping the roof cold in winter to prevent ice dams.
Solar & Super-Insulated Healthy Homes
It does work fine as a hot roof, most shingle mfgr's will warrant a hot roof now, but you can also ventilate if you build some sort of chase (like a beefed-up propavent) or you can strap on top of the roof sheathing vertically and add another layer of sheathing if you really want a ventilated roof.