Rainscreen size behind brick veneer
New home construction in Climate zone 5
Suburb of Detroit, MI – ave 133 days of rain per year, about 32″ precipitation per year.
2×6 studs. Our insulation contractor wants to use Owens Corning Fiberglass BIBS – we can get R24 in the stud cavity. At that amount in our zone, we would need at least R8.8 outside the studs (or more) – 27% or more. Or use less BIBs for the ratio.
We have about 2-2 1/2” available behind brick veneer for rigid insulation and a rainscreen. I was hoping to have a minimum of 2” of rigid insulation – our contractor prefers XPS.
We have generous roof overhangs – most are 48” from the sheathing, some are as little as 24”. This is a ranch.
There will be weeps.
I have read Martin’s “All About Rainscreens”
How can I maximize my R-value of the external rigid insulation and have a big enough rainscreen?
What is the smallest acceptable/advisable size for a rainscreen? I was under the impression that I needed 1” for brick veneer.
A secondary question is – Would using Rigid Mineral wool change this calculation? (I don’t think we would beat R8.8 but I seem to remember reading that mineral wool affects the assembly differently than rigid foam) or affect the size of the rainscreen? Affect the choice of sheathing?
Thanks in advance for any responses.
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