Green Building Q&A: How do you detail a plenum space with ducts that is below an unvented/insulated flat roof
This is a multi-family project in zone 4b which will have a drywall ceiling. Above the ceiling is a 2' space where ducts will run. CCF will insulate the underside of the roof deck and the walls of this plenum space. So, ducts will be in conditioned space. I am thinking about how we build a conditioned crawl space and intentionally condition it. This does not make sense to me for the attic area but I am concerned about moisture making its way into the plenum space. My instinct is to make the drywall ceiling airtight at penetrations and insulate ductwork even though it is in conditioned space. But also the drywall ceiling should be able to allow drying to the interior. Do you have any input on details for this type of attic space? Thanks!