Wall Assembly with Smart Vapor Membrane and Exterior Foam
Hello, I had a question regarding our wall assembly for a build that is underway. Due to extended lead times and shipping restraints, we were not able to use our original wall assembly which included 1.5” Rockwool exterior insulation. Fast forward to today and we have some decisions to make and I am hoping to hear some others’ thoughts and opinions. We are building in Climate Zone 5A.
Wall assembly is as follows from interior to exterior:
(The majority of our interior wall finish will be drywall)
0.5. Proposed* Intello Plus Membrane
1. 2×6 wall 16”oc
2. R23 Rockwool Comfortbatt
3. Zip Sheathing (Taped & Rolled)
4. Proposed* 2” of EPS foam boards R8 (taped)
5.2×4 horizontal strapping
6. Vertical corrugated metal siding
My question is about layer number 0.5 and 4.
Is the Intello layer necessary from a condensation mitigation standpoint?
Is the 2” of EPS foam a wise choice under metal siding, or would it be better to omit the exterior insulation and stick with just the interior insulation?
Thank you Dan
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Replies
Code will (barely) allow you to build that with Class III paint (instead of Intello). I'd provide more margin. There are various ways to do this - Intello or MemBrain, Class II paint, interior side air barrier, more foam, etc.
Any drying to the exterior helps - so use unfaced EPS or GPS.
Jon R,
Thank you for the response. The EPS we are planning to use is unfaced. So you would suggest going with both the exterior foam and the Intello membrane. If we decided against using foam, would you suggest still using the Intello layer?