In some instances, these air flow channels are set up over a layer or two of rigid foam. It’s also feasible to purchase nailbase (a style of SIP with OSB on a person side in lieu of two) that features integrated air flow channels among the OSB and also the rigid foam; a single model of these panels is Amazing-Vent from Hunter Panels.
Many spray foam roofing contractors within our industry are touting their potential make improvements to performance on previous scorching tar and graveled flat roofs by incorporating three to 4 inches of shut cell spray foam. The majority of these outdated properties are flat roofs joisted with dimensional lumber, with parapets and possess stucco vents Reduce into your rim joists.
Looks like you have the framing and roofing in place. Your choices are described during the posting over--you are able to insert venting by putting in baffles under the sheathing to carry back the insulation, or it is possible to install at the least R-20 of air impermeable insulation.
Thanks - This is certainly new construction, I am the designer / builder, and the more I check out it, I am liking all rigid - significantly less fussy. The very best layer of rigid more than fluffy helps make my eave as well thick in any case. The air barrier to the T&G ceiling is actually the sandwich of felt and taped three/eight" CDX.
I concur with you: I might prefer to see more details on this issue. I'm not aware about any failures that have happened in appropriately dense-packed unventilated rafter bays.
A. It is sensible to you personally since it satisfies your requirements. As that you are conscious, it isn't an excellent technique to insulate your roof assembly. But you may have described it as A brief prevent-gap measure.
Doug... For many cause I did't see your publish #17. Looks like two of us no less than Feel there may very well be a quite simple affordable Alternative.
On an unrelated matter: The Cold Local weather Housing my blog Exploration Centre has generated a video (beneath) exhibiting 1 means of developing an insulated cathedral ceiling. The strategy shown while in the video clip is particularly suitable for builders in climates subject to ice dams.
Must I take advantage of airtight baffles or not, I do not see a way to have moisture escaping in the assembly with airtight baffles, fiberglass and xps on The within, no matter what the dew stage will likely be inside this assembly and possibly make condensation that cannot evaporate without having air flow.
"Once you have set up the code-mandated thickness of rigid foam higher than your roof sheathing, you’re cost-free to put in just as much fluffy things as you need involving the rafters."
If you prefer, it is possible to Track down your ventilation channels in addition to the roof sheathing rather then under the roof sheathing. If you choose to try this, Guantee that any roofing underlayment that you put in previously mentioned the roof sheathing is vapor-permeable — such as, #fifteen asphalt felt, VaproShield SlopeShield, or Solitex Mento — Which your local developing Office accepts this method of roof venting.
Magic bullet status blog isn't realized. It's a style for a very low slope roof. It's a great deal together the lines of Doug McEvers utilization of high perm fibre board to build vent channels previously mentioned dense packed cellulose.
One more problem that comes up in that situation is whether or not that could endorse condensation over the underside in the one" XPS when it is actually cold plenty of exterior as the underside of your XPS may be down below the dew level? Q-three: How to proceed when we re-roof.
As the house flexes with variations of temperature It truly is possible, even likely that many of the foamed-in air sealing will leak. It would be worthy of doing 2" of open up mobile foam on the interior facet of which would be a more adaptable and responsible lasting air seal.