Crawl Space Radon Mitigation: Why It Costs More
You just received a radon mitigation quote, and it's $1,200 more expensive than your neighbor's. The reason? Your house has a dirt or gravel crawl space, and their house has a poured concrete basement.
The Physics of Sub-Membrane Depressurization (SMD)
Radon mitigation requires creating a negative pressure vacuum. In a standard house, the poured concrete basement floor acts as a hard lid perfectly sealing the dirt below. A fan simply sucks the air from beneath the solid lid.
A crawl space has no concrete lid. It's just exposed dirt.
You cannot suck air out of an unsealed dirt floor. The fan would just endlessly pull the conditioned air out of your house, drastically increasing your heating and cooling bills while doing nothing to stop the radon coming from the deep earth. Before attaching a single pipe, the mitigator must architect an artificial floor.
The Heavy-Duty Polyethylene Vapor Barrier
To create a seal, contractors must enter the cramped crawl space and unroll thick (minimum 6-mil to 12-mil) high-density polyethylene sheeting across the entire exposed dirt footprint. They must cut precisely around every structural pier, plumbing pipe, and ductwork drop. They then glue and tape the edges of the plastic up onto the foundation walls with incredibly durable polyurethane sealant or furring strips.
💰 Why Crawl Spaces Cost $800 to $1,500 Extra
- Labor: Crawling on your hands and knees dragging heavy rolls of plastic in a 3-foot high dark space takes an entire day.
- Materials: Specialized vapor barriers, massive amounts of polyurethane caulk, and structural tape add hundreds of dollars in hard costs.
- Complexity: The PVC pipe must be secured beneath the plastic barrier, often utilizing a perforated pipe matrix to span the entire length of the home.
The Bonus Benefit: Moisture Control
While it hurts to pay more, mitigating a crawl space provides massive secondary benefits. The plastic barrier (technically an "encapsulation") stops ground moisture from evaporating into your home's framing. You stop the radon, but you also prevent floor joist rot, wood-destroying insects, and mold growth.
Have a Dirt Crawl Space?
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