You describe your proposed air barrier as "taped felt." I don't Assume asphalt felt is usually successfully taped, and I don't believe that asphalt felt tends to make an excellent air barrier.
It appears like you posted your inquiries on two diverse internet pages. I've supplied a solution on one other page in which you posted. Here is the website link to my answer:
I'd personally drastically appreciate tips from specialists: Chunk the bullet and threat of spray foam insulation, or send the builders again up around the roof in December to chop ridge and soffit vents?
Numerous spray foam roofing contractors inside our current market are touting their capacity make improvements to performance on old very hot tar and graveled flat roofs by including three to four inches of shut cell spray foam. A large number of old homes are flat roofs joisted with dimensional lumber, with parapets and also have stucco vents Slice to the rim joists.
Brands of soffit vents and ridge vents commonly specify the net no cost vent area of their goods on merchandise packaging or in requirements accessible on-line.
Recall: just because your roof assembly is dry, doesn't suggest it's properly insulated. Your assembly might have large air leaks that work as thermal bypasses. (Or not. It's not easy to inform with out a web page take a look at.)
I've a 50 calendar year-aged seasonal cottage in a northern local weather. The simple six/twelve gable roof is composed of true 2x6 rafters (24" oc), sheathed with 1/two" plywood and protected with asphalt shingles. There isn't a insulation inside the ceiling and I suspect minimal to no successful insulation in the 2x4 partitions. In the summer the warmth gain inside helps make residing Just about unbearable. I think that the most important bang to the buck might be to handle the ceiling insulation difficulty first, but would like to manage the inside overall look.
Should your weather isn't too severe It can be likely alright to own just the R-ten foam about the structural metal, Though there's some hazard that the steel could sweat in chilly weather. I'm assuming Additionally you intended to insulate the 2x12 joist bays to Obtain your basics overall R-price to an affordable level.
If you'd like to Mix air-permeable and air-impermeable insulation, there are two possible strategies to move forward. One possibility (in accordance with the code) involves: “As well as the air-permeable insulation put in instantly below the structural sheathing, rigid board or sheet insulation shall be installed directly earlier mentioned the structural roof sheathing as specified in Desk R806.5 for condensation Regulate.â€
Yet another way to incorporate R-benefit towards your roof assembly is to include a few levels of rigid foam inside the roof assembly — possibly above the roof sheathing or down below the rafters.
I'm which include a photograph of the solution: spray foam held down in the prime edge of the rafters so that air could be drawn up from soffit vents to gable vents while useful reference in the truncated attic cavity.
Martin, re: transforming the attic above the second story bedrooms to the conditioned attic and sealing the soffit vents.... Just before this hottest idea about insulating with rigid foam in addition to the cathedral ceiling, we had been intending to Lower a ridge vent into the gable ridge, in order to satisfy ventilation code demands. At present We've eave vents additionally two fairly ineffective gable vents, 1 on both sides.
A. Either tactic will function, providing you get at the least the minimum code R-benefit for your personal roof, and providing you use development tactics that pay attention to airtightness.
Q. "If I execute the unvented roof as created and put four inches of polysio over the roof deck, am i able to then use open-mobile foam between the rafters?"