Martin’s recent article “Combining Exterior Rigid Foam With Fluffy Insulation”
This is a question regarding outboard and inboard insulation and Martin’s recent article “Combining Exterior Rigid Foam With Fluffy Insulation”.
I’m up in Canada – vapour barriers are the norm.
Assuming one is ignoring overall R-values and thermal bridging, if one installs a perfect vapour barrier (and I know this is not possible) then, in theory, one does not need any outboard insulation. If I understand correctly, a perfect vapour barrier will stop vapour drive AND air flow towards the exterior so there will be no warm humid air to condense on the sheathing and no need to keep said sheathing warm.
Am I understanding the theory correctly?
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