Rigid Foam board /polyiso insulation. I just cant seem to wrap my head around this one.Im reframing my roof , new rafters on up, and would like to use square edged boards for the exposed ceiling,and insulate with some rigid foam and then ply (for shear and asphalt shingle nailing) but am worried about condensation and the loss of shear by the ply being away from the rafters by 2 1/2 or more inches. Does any body have any experience with this sort of assembly? i live in southern california coastal area,but i dont know the zone I would be considered for but my avg. temp is probably 68 ,and a little more humid than inland obviously.any input would be appreciated,thanks, john.
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Your bord sheathing, then black underlayment, then foam boards, then the ply or osb, underlay again, then shingles. Be sure every seam/joint in the foam is foamed together with spray foam from a can so no air leaks.
even better, after the foam is in place, then run strapping 16" OC to create a cold roof for venting, and then the sheet sheathing, underlayment and shingles.
Next step better yet - get SIPs to overlay your board ceiling
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Thanks for the input,Piffin. It didnt even cross my mind regarding SIPs.The cold roof is the idea that i think ill end up goin with, because of the temp swing with humidity.Cold roof and Rigid .When you say black underlayment we,re talking about asphalt impreg'd paper? 15lb or 30 lb Now I just have to vent the ridge (simple gable) and intake at the eaves under the drip edge. Anybody have a good source for screening & ridge venting products?. thanks,John.Has anybody made their own SIPs?
Not possible AFAIK to make your own SIPs.Big equipment and technology required.Black is mentioned for colour. You do not want to be inside looking up at square edge boards and see gaps that show white or some other colour of underlayment.Whether to use RooftopgaurdII or tarppaer depends on budget, winds, and how long before it gets covered all the way. My vote is on RTG II
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!