Insulating below sheathing between trusses with batts / unvented roof
Is there an effective way to use batts below the sheathing when using trusses?
I am building a roof structure that has 4 to 5 inches of poly on top of the sheathing and was planning on using R38 batts below in a unvented roof assembly to get over R60. I’m in Zone 5, high prairie, low humidity, high wind area. The trusses are being proposed as an option to move the build faster by my engineer. The original design had stick with post and beam for a large vaulted room. The trusses drop the cost significantly and will still allow the vault using parallel cords.
I have considered dense pack but am curious if there is a good system for supporting batts between the trusses?
Thanks
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The insulation contractors that I've spoken with around here often use the batts meant for metal studs, because they tend to fill the truss web cavities because of the extra batt width. The lowest layer (the one at the bottom chord) they use the normal studwall spacing batts, so they don't over-compress between the truss chords.
Not sure if that is helpful at all. Trusses are difficult to insulate well with batts because of the cavities formed by the webs.
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