two. Install sturdy web site-crafted ventilation baffles in Every rafter bay prior to deciding to spray the foam. That way you end up getting a vented cathedral ceiling.
If you put in 2x4s (or 2x3s on edge, mounted with long screws) perpendicular for the rafters, you may address the vast majority of thermal bridging issue with no have to increase a layer of rigid foam.
Ought to I treat the flat roof as a cathedral ceiling and select spray foam (or board), fiberglass, and no humidity barrier?
Yes a cathedral ceiling detail would be quite comparable though the obstacle of numerous cathedral ceilings is the extra structural features, electrical boxes, and the need for wood board ceilings all which start out compromising the drywall layer which in the detail is utilised with the air barrier.
I desire to adequately insulate my cathedral ceilings and was thinking to spray two inches of shut cell foam to sheathing, then fill with dense packed cellulose. I am thinking if I can connect craft paper and pine paneling to the 2x8 rafters and after that fill the bays with cellulose.
three. Making use of continuous Ice & Water Protect is sometimes risky, but it's Okay For anyone who is subsequent the PERSIST tactic and putting all of your insulation on the outside of the peel-and-stick. The strategy can perform, but you need way more foam on the outside of your roof.
The R price of your Lower'n'cobbled foam + exterior foam this website has to be at least forty% of the center-cavity R price for dew issue Regulate on the foam/fiber boundary in zone five. If It truly is developing a tiny bit shy of that prior to adding the outside foam it's actually not a large offer inside the short-term, but if it'll be five-10 years ahead of re-roofing to lift the foam-R to previously mentioned 40% of the whole It can be worthy of employing vapor barrier latex primer to the gypsum board, or a wise vapor retarder between the gypsum board & fiberglass.
(d) There might be more than enough air leakage for the "soffit" and ridge to provide air stream that functions the way in which a ventilation hole ordinarily would.
It really is much more crucial to have an interior air barrier than an interior vapor retarder. Be sure that you've produced a fantastic air barrier by sealing all penetrations and cracks.
First, could it be simple to identify no matter if a roof is ventilated? If no soffit vents or aspect vents are visible to the roof from the ground, does that imply the roof is not ventilated?
I'm such as a photograph of the answer: spray foam held down in the top rated edge of the rafters so that air could be drawn up from soffit vents to gable vents inside the truncated attic cavity.
Yes, it truly is Protected (although before you decide to check with an issue about a particular roof assembly, It could be click for source superior to learn your weather zone).
Your blogs on this subject are already particularly handy and I take pleasure in your suggestions. ( I do examine before I post thoughts : )
Can I get absent without having a number of These levels offered my climate zone? For example, am i able to use all Roxul, devoid of XPS? Do I Definitely need the drywall?