We happen to be a short while ago installing loads of shut cell foam on to the roof sheathing with fantastic benefits. Having said that I ponder For those who have listened to about what transpires when the unavoidable roof leak happens?
November eighteen, 2011 Picture 1 of three A leaky ceiling doomed the roof sheathing. The ceiling of this 10-yr-outdated house was Slash for an electrical box, and also the oversized hole was by no means caulked. Humidity-laden air entered the rafter bays by means of these cracks. Once the dampness encountered chilly roof sheathing, it condensed, leading to moisture accumulation and decay. (The rubberized membrane during the photo was applied as A short lived patch for the gap within the roof, and did not add into the failure system.) Picture Credit score: Peter Yost A leaky ceiling doomed the roof sheathing. The ceiling of this 10-12 months-previous home was cut for an electrical box, and also the outsized gap was in no way caulked. Humidity-laden air entered the rafter bays through these cracks.
Very first, thanks Martin for that wealth of knowledge this Web page has. I have been browsing it frequently for the last few decades, ever due to the fact obtaining my first residence. I'm also located in northern VT, zone 6 but I feel we may very well be pushing 7 as a result of localized disorders. I have lately experienced an Vitality audit executed and desired to confirm among the list of suggestions. We have an area using a cathedral ceiling, in addition to a lose dormer developed into the cathedral. The cathedral ceiling is insulated with r38, and also the get rid of dormer with r19. Both are kraft confronted fiberglass. The roof is 12/12 over the cathedral, unsure but fewer around the dormer, and has snow protection (often about eight") from the beginning of January till mid March.
In the absence of the airtight ceiling, roof air flow can do more hurt than good, due to the fact air motion in rafter bays can persuade indoor air to leak as a result of ceiling cracks.
My knowing as I look at this web site is the fact that I do not have to bother with making an air channel above the sheathed part due to the rigid foam.
I would increase to Martin's listing of products for rafter vent channnels, fiberboard sheathing. I take advantage of I joists for vented cathedral ceilings and staple 1/2" fiberboard to The underside of the top wire of your I joists. It can be ripped on a desk observed and installs quickly, fiberboard does Have a very substantial perm score and may enable small amounts of dampness to go through in the vent Place.
Our cooler mornings might make the inside of my metal roof sheeting to sweat somewhat due to the fact It will probably be in connection with the hotter unvented fiberglass-insulated purlin "cavity" beneath. As soon as our hot Caribbean sunshine begins to kick in I would like this humidity to dry and/or diffuse out of the cavity, with the gypsum sheeting, in the cathedral residing House beneath, to then be blown away from my 4x3 gable window. A vapor barrier would wholly retard this process.
Does this method sound as helpful as vent channels constructed on the inside on the roof sheathing? I'm having difficulties to find out why this would not get the job done also or in almost exactly the same manner being an in-board website-crafted vent channel. It is basically like a rain screen or vented cavity, exact same as around the walls. Any ideas on this?
This assembly was recently built just south of Portland OR. I posted it a couple of months in the past. Right here it's again (While using the builders comments) I feel It really is a reasonably straight forward build as you get previous the concept of introducing assistance cavities to your Create.
If this were my residence, and In case the fiberglass batts are obvious, I would pull the entire insulation out of some rafter bays to check out what is actually up there.
"R-19 batts are certainly air permeable, and on extensive unobstructed rafter bays you've got fairly a stack effect. It isn't going to take a large degree of air leakage to deliver some drying there. Also, When the batts are unfaced or kraft-confronted, the drying toward the inside could be sizeable.
"Once you have set up the code-mandated thickness of rigid foam earlier mentioned your roof sheathing, you’re cost-free to webpage install as much fluffy stuff as you desire concerning the rafters."
A. Possibly method will get the job done, as long as you get at least the least code R-benefit to your roof, and providing you use development approaches that listen to airtightness.
The old Canadian guideline -- at the least 2/3 of the overall R-price on the outside facet from the vapor barrier -- can be a rough-and-Prepared way to address this issue; it's also possible to technique that site the problem by undertaking a dew-place Investigation or maybe a WUFI Investigation.