1:12 Unvented Roofing

This is a homeowner's question posted on a building-science forum, not a news story, so there's no new program, product, or deadline to report. A homeowner with a flat-ish roof (a 1:12 slope, meaning it rises just 1 inch for every 12 inches across) and no attic venting is asking how to build the roof so it doesn't trap moisture. Their plan is 3 inches of rigid foam insulation (polyiso) on top of the roof deck, plus fiberglass batts between the rafters below, and they're weighing three roofing surfaces: roll roofing, rubber (EPDM) membrane in two thickness options, or metal standing-seam.

No one had answered the question yet at the time this was posted, so there's no verdict on which roofing choice or seam detail is best, and no specific product recommendation to pass along.

For homeowners with a similar low-slope, unvented roof, the underlying issue is worth knowing about: these roofs need careful attention to how moisture escapes, since there's no attic airflow to dry out any dampness that gets trapped in the rafter bays. If you're planning a re-roof or renovation on a flat or nearly flat roof, this is the kind of detail worth raising with whoever designs the job, since getting the insulation layers, roofing membrane, and ceiling seal wrong can lead to hidden moisture problems later. But this particular post doesn't offer a specific answer or new information you can act on yet.