A. To take advantage of the insulating value of the rigid foam above the attic, you definitely desire to seal up any attic vents, and you also certainly don't want to make a ridge vent.
It's really a code violation to set up an air-permeable insulation like fiberglass batts between unvented rafters. It's also a foul thought, mainly because dampness can accumulate in your roof sheathing if you try this method, and you may end up with sheathing rot.
I'd prefer to use the exterior wall and roof sheathing as my Most important air barrier; cdx plywood with all seams taped, which form of forces me to keep the roof venting along with the roof sheathing, when you explain in paragraph 7 of this post. I might love to use Solitex Mento for a permeable roofing underlayment, in addition to a WRB on vertical walls, and a couple of levels of cross hatched 1x4 strapping about roof ply and Mento; one particular functioning down the roof slope, nailed on the rafters, and the second run horizontally about them to help corrugated steel roofing.
If I transformed my venting element to your web site built type, in between the rafters, as in the quite a few weblogs on this topic, my air barrier would want to changeover again inside right before it bought to your sloped roof; really cumbersome in the gable walls. Probably not absolutely sure how I would do this.
I checked out the unvented schematics and I am not positive that matches the Monthly bill for up listed here (Canada - west Coastline).
1. Take out the can lights and throw them absent. Recessed can lights should really under no circumstances be installed within an insulated cathedral ceiling.
I used to be skeptical of Monthly bill Hulstrunk's claim that AccuVent baffles could endure remaining dense-packed within an enclosed cavity.
On the topic of fluffy insulation, are there any sources you may refer me to which tackle the variances between very low, medium and higher density fiberglass batt insulation within the standpoint of lack of R-Price as a consequence of wind-wash (no matter whether resulting from air infiltration or convection due to significant temperature variances entrance to again)?
It looks like an excellent plan. According to what sort of rigid foam you select, you'll end up having insulation during the number of R-16 to R-24. While that's fewer than code demands, It is much, much better than what you have got now.
Thanks for your proposed addition into the listing of supplies for building internet site-built vent baffles. I've edited the text of my site to incorporate your suggestion.
As I defined within find the article on this webpage, You can not use fluffy (air-permeable) insulation within an unvented roof assembly unless you involve rigid foam or spray foam earlier mentioned the fluffy insulation.
I haven't got experience creating while in the Carribbean or developing steel buildings, so I'm not the most effective man or woman to remark. But here are some reflections:
Ken's depth (#10) does a fantastic task of chilly climate safety. It's got what we are trying to find: Excellent airsealing at the interior, fluffy things in the middle, and good drying channels for drinking water vapor at the highest. By shifting from a reduced permeability sheeting to your high permeability membrane (at best) with venting previously mentioned, there isn't any extra issue for roof rot while concurrently wind washing is prevented inside the bays with the air & water restricted membrane with taped edges and seams. It seems to me for being a really sturdy assembly.
I are convinced most contractors would be concerned about the buildability within your strategy. The Picture shows a minimal-slope roof more than a flat ceiling; This permits employees to stand over the ceiling joists.