How is spray foam installed to an open ceiling? Is some kind of mesh or solid surface attached to the top of the joists first? Would it make any kind of sense from a heating or cooling standpoint to eliminate gable vents and spray to the peak, essentially adding the empty triangle to the conditioned space? In our current home(cape) this space gets extremely hot in the summer. In the winter, the snow will melt at the peak triangle, but not at the insulated slope or the lower eave triangles. It could be due to the hot chimney running through this space, but I’m not convinced.
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bumpity bump
I built a woodworking shop that has total icyene foam. The attic is about 12" deep with foam applied to the sheetrock ceiling. I have 2x4 walls. The shop is air tight. I heat and AC the shop and I highly recommend it. Better get ALL the work done in the attic first, as you will never see it again once the foam is in place. I don't see a need to foam the gable walls. There is snow on the roof no matter how hot the shop gets. So not much heat gets up there. I intalled gable end vents and soffit vents appropriate for the buildin size.
They just spray it onto the underside of your roof.
So, if they are spraying the ceiling the gyp needs to be in first? Do they abandon a worker in the attic with each install? That sounds expensive! I will not have any mechanical in the attic spaces, but there will be a few plumbing vents, a chimney and a dozen can lights penetrating the ceiling. I'm certainly comfortable spraying tight to the sealed can lights since I'll be running CFLs, but what if a future owner put in a 100 watt flood?
There is about 830 cubic feet of attic space at the peak, and another 800 or so tied up in the eave spaces behind the kneewalls. This seems like a lot of volume to condition, but could this be the best energy approach? I see this helping to control ice dams in the winter (Vermont) and keeping the attic cooler in the summer. I would eliminate the need for gable or ridge vents.
Any thoughts on which way to go for energy efficiency?
You reading 87134.1 ? The hot roof thread is the way for you to go. If you are just insulating the attic floor you can use blown cells to get a high R value.
Thanks! I'll keep reading with interest. If I used 2" of high density and then topped off with low density I could get R-35 in a 2x8 roof. My cape could easily be framed with 2x8 rafters, but I had 2x10s just to fit R-30 batts. The $1000 savings on lumber would help mitigate the high cost of spray insulation. A couple hundred for durovent, gable end vents and ridge vent help too. It's nice to say that a spray foam system will pay itself off in energy savings, but some up front dollars are often more important on a budget.