Polyisocyanurate and placement for baffle
Hello all, I am finally getting around to adding my insulation and all on the interior of my brick walls(was held up repairing trusses). The plan is to make my own baffles going about 6 to 8 feet up with ridge vent. I am in zone 2 with r11 batt attic insulation with blown in on top of that. Question is, do I run the foam straight up from the wall right into the baffle…or go up and over my top seal(concrete header beam) to the edge of the house, and then up with the baffle. I am designing it with typical soffits at 12 inch overhang(short for extra hurricane protection) Going up and over seems better insulated but I dont know if it will hinder evaporation near the truss heels. They are sitting directly on concrete…no paper or anything.
Thx
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I'm not sure I completely understand the question. A sketch would help.
Ideally, you want full insulation depth at the top of the wall. With trusses sitting on top of the wall, and with your foam insulation on the inside, that's not quite so important. Regardless of what you do, there's going to be some fussy detailing around the trusses. I think I would be tempted to go straight up with interior foam insulation until you hit the underside of the baffles. This would leave the truss heels in the open airspace inside the soffits, and that might provide a bit extra drying potential. It's also an easier detail than trying to cut and cobble foam going up and over.
Either way, you should provide some sort of dam/baffle above the soffit vents and ruggedize the vent design. Hurricane-force winds blow water up and in through soffit vents and that can soak the top of the walls. If your foam is rugged enough and sealed properly, it might suffice to stop that water at the top of the walls. Some soaking of the concrete headers is probably OK, but you don't want the water running down between the masonry and the foam if you can help it. Or farther to the interior, of course.
Insurance companies (FEMA and IBHS) have been finding that even in wind code compliant houses that structurally survive hurricanes, there is enough interior damage from water blowing in through the vents that the cleanup cost approaches that of houses with structural damage.
https://www.fema.gov/media-library-data/1560174739479-8856110e0c3fa30e750370dc5129348a/MichaelRA2_060719_508_FNALforposting.pdf
Thanks Peter....that's what I was thinking in regards to the truss tails. As far as the rain mitigation, in the event of a hurricane, I too saw a similar article. I am thinking of doing blocking in between each tail with holes and a tyvek membrane or something....in addition to my metal or wood soffit....I dont know yet....gonna work on that part later.....can always do the blocking and drill a ton of holes if I go another direction....Irma forced wind blown rain in my house 2 years ago...it ain't happening again. I'll do a drawing or attach a pic.