Crawl Space coversion from vented to non-vented
I am getting ready to begin insulating, sealing, and encapsulating the crawlspace under my house that I am renovating. The current space is vented and I will be converting to unvented / conditioned space. I have already completed the roof side of my work to unvented.
The house is wrapped with 2″ of polyiso along with another 1/2″ layer to get a good air seal on overlaps. R15. I will be insulating with air permiable the interior stud walls according to code for a combined R30.
The polyiso and siding extend below the sill plate and cover about 2″ of the concrete foundation. The concrete extends down another 6 to 8 inches before there is dirt. See attached diagram.
I will be putting foam board along the concrete inside the crawlspace and then air sealing the entire space with 12mil vapor barrier. The crawlspace will be dehumidified as well as have vents to the main floor inside the house. I will also be adding a passive radon system for code purposes as part of the process. (in case someone comments on this).
Should I leave the space where the sill timber is alone and not put any insulation there to allow this to dry inward? My thought is not to seal this for that reason. If I want to insulate should I just put in some rockwool for added insulation?
I am zone 5, 2000ft, not a high snow area. High prairie in eastern WA.
Any thoughts will be helpful. I plan on starting this in a few weeks.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part