Air tight ceiling or not, unvented roof assembly /w open cell spray foam

We’re looking at constructing an unvented 2:12 pitch skillion roof with a cathedral ceiling in zone 3A using this detail https://www.greenbuildingadvisor.com/app/uploads/2020/12/Cathedral-ceiling-Detail-4-B.jpgexcept we would be using open cell foam insulation.I’ve read… We’re looking at constructing an unvented 2:12 pitch skillion roof with a cathedral ceiling in zone 3A using this detail https://www.greenbuildingadvisor.com/app/uploads/2020/12/Cathedral-ceiling-Detail-4-B.jpgexcept we would be using open cell foam insulation.I’ve read…Read MoreGreenBuildingAdvisor