Gone are the days of vented crawlspaces where builders once installed plated gateways for mold and moisture to infiltrate and wreak havoc on air quality and floor joist integrity. Leading with the latest in building science standards, our encapsulated crawlspaces use radon-suppressing polyethylene in conjunction with closed cell foam to extend the envelope of the house, enabling precise regulation of crawlspace air and moisture content.
11 x 10(^-12) M^2/s
Oftentimes homes -especially older structures -will have vented crawls with virtually no radon barrier, but are host to decaying batt insulation hanging tepidly between the floor joists. Is that just shoddy design, or is there reason to forego an encapsulated crawl in favor of an insulated sub-floor? Generally the only circumstance under which it would be advisable to opt exclusively for sub-floor insulation is if there are minimal to no duct lines and/or HVAC mechanicals located in the crawl. In that situation, it may be advisable to insulate the sub floor with either 1) mineral wool batts held in place by a polyethylene vapor barrier or 2) sprayed-in-place closed cell foam -covering the subfloor between the joists and wrapping around the joists -to eliminate water and radon vapor as well as mitigate updraft and/or conditioned air convecting through the floor and outside.
Unfurling poly sheathing along the dirt base and taping it together by no means constitutes a "conditioned crawlspace", yet all too many contractors do just that, then call it a job well done. A correctly conditioned crawl will accomplish three things; 1) suppress and redirect radon vapor emanating from the topsoil, 2) halt air infiltration and insulate against moisture via condensate, 3) create a space where ducts and mechanicals are protected from pests and elements, and can be smoothly accessed for regular service. We accomplish the first via industrial-grade, tear and puncture resistant woven polyethylene sheets that are roll taped or fused and sealed at column supports; the second is achieved by sealing and insulating the entire perimeter wall with ccSPF; with the poly affixed and the foam adhered, the crawl is effectively shielded from the outside and can be controlled and "conditioned" by the home's own air exchange system.