Crawlspaces require a different approach than slab-on-grade foundations. Sub-membrane depressurization and proper vapor barrier installation are essential for effective crawlspace radon mitigation in Denver homes.
A crawlspace foundation presents a distinct radon challenge. Unlike a poured slab, a crawlspace typically has exposed soil — a direct pathway for radon gas to enter the living space. The solution is sub-membrane depressurization (SMD): a heavy-duty polyethylene vapor barrier (typically 20-mil) sealed to the crawlspace walls, with a depressurization pipe and fan system drawing radon from beneath the membrane.
The process involves more preparation than sub-slab work. The existing ground surface is leveled and cleared of sharp debris that could damage the membrane. The barrier is then rolled out, overlapped at seams by at least 12 inches, and sealed with tape and mechanical fasteners at the walls. A suction point is created beneath the membrane, pipe is run through the crawlspace and exterior wall, and a fan creates the negative pressure needed to intercept radon.
Many Denver crawlspaces also benefit from improved drainage, additional ground cover, or sealed vents — which can further reduce radon entry and improve moisture management. We assess each crawlspace individually and recommend the most cost-effective approach.
A crawlspace mitigation system is right for you if: your home has an exposed-dirt or partial-barrier crawlspace with elevated radon test results; your existing vapor barrier is thin, damaged, or partial and not providing adequate protection; you have high moisture in addition to radon concerns (a proper membrane addresses both); or your home is a combination foundation — slab and crawlspace — requiring treatment of both areas.
We begin with a crawlspace inspection: assessing the condition of any existing vapor barrier, noting drainage issues, measuring dimensions, and checking for obstructions. We then quote the job with a specific scope: barrier square footage, suction point count, fan selection, and exhaust routing.
On install day, we prepare the ground surface, install the 20-mil vapor barrier with sealed seams and wall attachments, place the suction point beneath the membrane, run PVC piping to the exterior, and install the fan. Post-install, the crawlspace is significantly drier and the radon gas pathway is interrupted at the source.
Crawlspace membrane systems: $2,000–$3,000 depending on square footage, accessibility, and existing barrier condition. Post-install re-test included. Written guarantee below 2.0 pCi/L included.
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