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Community and Q&A

Batt Insulation Attic Roof with Air Gaps between planks

unknownco | Posted in GBA Pro Help on

Hi all,

We’re looking to do some efficiently upgrades on our home (Climate Zone 3B Los Angeles) including better attic insulation, a new HVAC system and a new roof (metal).

Our ducting is unfortunately in our attic and so we need to bring the attic into the conditioned space by insulation the Attic ceiling and walls etc. We’re going to use mineral / rock wool batts for the insulation. We are also planning on a metal roof (Boral Steel / Unified Steel shingles with their R5 underlayment and batten system).

In order to do this right we will need to have the batt insulation directly against the underside of the roof deck but in our case, the roof deck / plywood seems to be on top of another layer of wood planks (see the attached image). Won’t the gaps between planks need to be filled in with insulation? I’m assuming if we ‘do not’ factor in this air gap that could be problematic as it could trap moisture? Is the amount of space negligible? I’m assuming that this is not a ‘new’ issue as there have to be other roof assemblies like this.

What is the appropriate way to insulate this with batts?



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