PolyIso necessary under metal roof in zone 4
I live in Portland, OR, which is region 4. We’re replacing our roof and highly considering a metal roof. The contractor included installing a layer of poly-iso under the metal roof as an option, but that would put us out of budget. The contractor put that as recommended, but not required, but I want to check how “not required” that really is.
We currently have r-50 cellulose insulation in the unfinished attic and have been told by energy efficiency contractors in the past that we have good ventilation as well. So I don’t know if everything is good given the attic, or if adding the poly-iso will be needed, or if we can skip the poly-iso, but install more ventilation to be safe.
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