We prepare to transform to an improperly vented cathedral ceiling to an unvented a single. Sealing up the soffit vents is actually a no-brainer. What's The simplest way to handle the ridge vent? Thanks!
In line with portion R806.five with the 2012 IRC, “Unvented attic assemblies (spaces concerning the very best-Tale ceiling joists as well as roof rafters) and unvented enclosed rafter assemblies (Areas among ceilings which can be applied straight to the underside of roof framing users/rafters as well as the structural roof sheathing at the best in the roof framing members/rafters) shall be permitted” so long as many ailments are achieved.
I might insert to Martin's list of materials for rafter vent channnels, fiberboard sheathing. I exploit I joists for vented cathedral ceilings and staple one/2" fiberboard to the bottom of the best cord from the I joists. It may be ripped with a desk noticed and installs promptly, fiberboard does Use a significant perm ranking and could permit small quantities of dampness to go through to the vent Place.
A. As I wrote from the article, "Most rafters aren’t deep more than enough to accommodate the insulation needed to fulfill bare minimum R-values needed by code, particularly if the rafter bays include things like a ventilation channel. ...
Making use of ventilated nailbase panels is a wonderfully great way to develop a cathedral ceiling. The exact same guidelines implement as when utilizing SIPs: make sure that the seams are sealed being as airtight as you may make them, and make sure that the total R-price of your roof assembly fulfills or exceeds minimum code R-worth necessities.
I concur with you: I'd choose to see more details on this challenge. I'm not aware of any failures which have occurred in appropriately dense-packed unventilated rafter bays.
It is just a code violation to set up an air-permeable insulation like fiberglass batts involving unvented rafters. It is also a bad idea, due to the fact dampness can accumulate in your roof sheathing if you are trying this process, and you'll end up with sheathing rot.
Within a phrase, no — the code explicitly forbids this method. Cellulose can only be used in an unvented roof assembly if there is an adequate layer of rigid foam over the roof sheathing or an sufficient layer of closed-mobile spray foam under the roof sheathing. Cellulose on your own received’t work.
Dan Reams, explanation thanks in your opinions. I also reside in snow place around Yellowstone National Park. I generally have very well over 3 feet of snow on my cathedral roof. I think the dew level is usually in the snow instead of while in the roof. The R price of the snow is frequently close to the R value of the roof. This can lead to significant ice dams. A straightforward thermal Examination displays that You can not set a sensible number of insulation while in the roof to prevent the ice dams and move the dew stage into your roof.
With my residence the middle part (20ft) is vaulted, a 3x12 slope and has 8 recessed lights throughout. I've had leaks in many locations During this section of your house, the leaks occur Using the thaw and refreezing. It got the point previous year wherever I needed to shovel the complete roof just after Just about every snow fall.
While roof air flow might help dry out moist roof sheathing, it’s essential to Restrict the movement of h2o vapor escaping from the household so the roof sheathing never ever will get damp in the first place.
Your plan to use two-inch-thick EPS as your air flow baffle will function. The EPS is considerably vapor-permeable, so it will permit a small amount of outward drying. (In almost any scenario, in the event you Develop a fairly airtight ceiling, there won't be any dampness On this assembly that needs to escape.)
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My sensation would be that the dew point profile would finish up inside the XPS foam board, that's why a VB need to be placed on to start with deck. In order of assembly: