IRC on Vapor Retarder for Vented Attic
I know this has already been addressed before, but my local inspector is hammering down that I need a vapor retarder (Class I or II) for a vented attic assembly in climate zone 5. I know that this is misguided. Unfortunately, I cannot find more black and white guidance than that set in section R806.2 “Minimum Ventilation Required”, specifically exception (1), to prove that it’s not required. My inspector is citing R702.7, which I have to admit is a tough thing to argue when R805.1 explicitly states ceilings shall be installed according to R702 standards. I refuse to put a vapor retarder on my ceiling, and it’s disappointing my building department makes no mention of windwashing prevention, air sealing, etc (far more important topics). I would appreciate any recommendations or definitions I’m missing from the 2018 IRC that would put this to rest.
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