Reno: vented roof with 4 inch rafters. Spray foam?
What are options for renovating an old (1940s) vented roof with 4″ rafters?
Contractor is recommending a 1st Phase of spray foam applied from underside to get R20 (and I’ll confirm open vs closed cell with him). And recommending 2nd Phase of rigid foam on top of the roof (to get at R60 total).
Currently, the attic floor and knee walls are insulated and not the roof. Attic floors are either 4″ blown in cellulose in attics and 8″ loose fill cellulose elsewhere. Knee walls are 4″ fiber batts with house wrap facing exterior (that is poorly sealed). Contractor is recommending we remove all this old insulation after the roof is insulated as it may present “problems” … though it wasn’t clear _what_ problems that would be other than “more isn’t better”.
Another contractor recommended also dropping the sloped ceilings that are above the knee walls attics and sister in deeper rafters … but this is problematic on some of the sloped ceilings because upstairs windows get in the way.
Curious to hear what others have done or recommend. EDIT: our house is in zone 6 — sorry, I was switching between our garden plans vs house plans where plants have a hardiness zone of 5 here 🙂
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