Roof EPDM insulation with open cell
Been pondering a lot about this, I built a home about 2 years ago where the architect specified R-42 open cell in the roof underside and EPDM on the exterior (flat Roof). I actually ended up putting 20″ of open Cell on the underside for R-70.
My roofer laid down 1/2″ polyiso (standard practice) then EPDM on top.
My question here is given the vapor retardation properties of the EPDM and only 1/2″ of insulation outside–is there cause for concern? The Total r value is around R-73. Climate Zone 5-Upstate NY
I assume this means any potential vapor would flow into the house and as long as the ERV’s are operational then the system is alright but let me know if there are any gotchas?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part