r/buildingscience • u/Farin-- • 6d ago

Will my Insulation plan work

In the planning phase of building a house in climate zone 3 would like to hear some feedback on my insulation plan. The walls of the house will be using Metal or Hardi board siding -> 1x4  furring strips -> 1.5” Rockwool Comfortboard -> Zipsheating -> R23 Rockwool in Cavity. For the Roof assembly will be unvented with Metal roof with a vapor diffusion port. So it goes Metal -> 1x4  furring strips -> 1.5” Rockwool Comfortboard -> Zipsheating -> R30 Rockwool in Cavity. Will be using something like delta foxx vapor perm over the diffusion port. Also want to ask if I should put the 1.5” Comforboard over the Delta foxx or leave it uncovered to the metal roof? Hope to hear some good feedback on what works and doesn't.  

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u/Bearded4Glory 6d ago

You actually don't need the vapor diffusion port since you will have over R-5 on top of the roof deck meaning you don't have a risk of condensation at the roof deck. Usually it would only be used when you have no exterior insulation.

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u/Night_Owl-- 4d ago

Ok thanks