My suggestions could well be to seal the prevailing vents. If insulation contractors close to you are putting in three to four inches of shut-cell spray foam above the roof sheathing, you won't need to be worried about condensation or moisture accumulation with your sheathing.
A vented cathedral ceiling only is sensible Should the geometry of your respective roof is simple. You need a straight shot through the soffits towards the ridge. That’s rather uncomplicated with a gable roof with none dormers or skylights, but if the geometry of the roof is complex — with characteristics like hips, valleys, and dormers — it’s not possible to guarantee air movement as a result of all of your rafter bays.
Don't forget, an insulated sloped ceiling isn’t always a good idea. Sometimes a good outdated-fashioned unconditioned attic is The easiest way to cap your property.
My house built-in sixty three in this article in Ohio contains a cathedral ceiling without any air flow. In reality there several cross-supports jogging perpendicular to the main joists and also other framing components that might make this unfeasible. So I need to make it an efficient unvented roof. 50 % with the roof has 2x8 joists and the other 50 percent has 2x12s. Right this moment there is a membrane covering (rubber) that's worked perfectly for over 20 years but is displaying signs of deterioration and may possibly will need changing quickly. Obtaining performed transforming on the inside and strolling around the roof I recognize that a lot of the sheeting needs to be replaced together with the very little insulation that's there now. We've experienced condensation difficulties previously so I now there are actually air infiltration and bridging issues.
I looked at the unvented schematics and I'm not confident that fits the bill for up below (Canada - west coast).
Your blogs on this topic have been really useful and I appreciate your guidance. ( I do review in advance of I submit thoughts : )
Code would not appear to be to apply as it's grandfathered in. It looks like I ought to redo the hall ceiling.
I agree with you: I'd choose to see more information on this concern. I am not mindful of any failures which have occurred in effectively dense-packed unventilated rafter bays.
It seems like a superb plan. Dependant upon what sort of rigid foam you select, you'll end up with insulation from the variety of R-sixteen to R-24. hop over to these guys Though which is under code prerequisites, It really is Substantially, much better than what you might have now.
Certain the instance shown is for a small pitch (not flat) roof. But adjust it to some pitched roof fewer than 6-12 and the small print are still a fantastic technique (I do think).
As I described within the post on this web site, you can't use fluffy (air-permeable) insulation in an unvented roof assembly Except if you include things like rigid foam or Click This Link spray foam over the fluffy insulation.
"The conventional roof air flow necessity used in developing codes and asphalt roofing manufacturers requires 1 sq. foot of "Web no cost ventilation area" For each and every three hundred square ft of ceiling place (attic flooring space) when vents are evenly divided — 50 percent of them significant within the roof with the ridge, gable, or simply a large roof, and half lower on the roof with the eaves.
Are you currently imagining the 'flat' vented cavities will never deliver the assembly having an exhaust route for moisture?
I've by now insulated the steep sides of my unvented mansard roof with six" fiberglass (and I experienced it inspected), would you propose I rip that out and use spray or board foam? I've gotten conflicting data on regardless of whether to treat it as a wall or simply a roof.