Radon Gas Mitigation

The information below describes and shows the solution to a high Radon Gas level inside the home. The Environmental Protection Agency (EPA) recommends that a confirmed radon level of 4 picocuries per liter (pCi/L) of air or higher be reduced to decrease the risk of developing lung cancer. This house had a very high level of 12.0 pCi/L and was reduced to 0.7 pCi/L after performing this mitigation. The cost of radon mitigation in a typical home ranges from about $500 to $2,500.

The most popular radon mitigation technology is called "sub-slab depressurization" or "sub-slab suction." The "sub-slab depressurization" technique removes radon-laden air from beneath the foundation and vents it outside the house by installing a fan and inserting a pipe through the foundation into the aggregate below, running it to a point outside the shell of the house. A similar technique, "sub-membrane depressurization," which is effective in buildings with earth-floored crawlspaces or basements, uses a plastic barrier over the soil as a collection cover. Another depressurization technique for preventing radon entry, "blockwall depressurization," uses a fan and duct work to draw suction on the hollow interior cavities of a concrete block wall. By keeping the air pressure within the block wall lower than the air pressure in the basement, the soil gas is removed before it can enter the basement.

The "sub-slab depressurization" and "sub-membrane depressurization" techniques were installed in our house and all work was performed by the author.

Materials Required

The materials required and approximate costs for this home follow:

1. 4" of #57 Gravel for Crawl Spaces (Optional) ($200.00 for 20 tons, 10 tons per crawl space)
2. 3" or 4" PVC Pipe, Couplings, and Adhesive ($50.00)
3. Concrete Caulk ($5.00)
4. 6 mil plastic ($50.00)
5. Construction Adhesive ($20.00)
6. Duct Tape ($5.00)
7. Electrical Wire and Connectors ($25.00)
8. Radon Fan ($175.00)
Total cost = $330.00 ($530.00 with optional 4" of crawl space gravel)

Basement Floor

Cut a circular hole in basement floor at a convenient location approximately in the center of the room. This hole is cut by drilling a series of holes with a masonry drill bit. The diameter of the hole should be slightly larger than the outside diameter of a 4" PVC Pipe that will extend into the gravel beneith the concrete and routed through the roof. Once this section of pipe is inserted into the floor, plumb and secure the top of the PVC pipe to a floor joist and then apply concrete caulk in the gap between the PVC pipe and concrete. Use this caulk to also seal any and all cracks in the concrete floor. The photo below shows the PVC pipe installed into the concrete floor:

Crawl Space(s)

Optionally install perimeter drainage in crawl space(s) and connect to footer drainage. Optionally install 4" of gravel in crawl spaces. Install 6 mil plastic over entire crawl space floor and glue to walls approximately 18" above floor. Install 3" PVC pipe through plastic and connected to optional perimeter drainage or extend to approximately 3" above floor. Plumb and secure the top of the PVC pipe to a floor joist. The photo below shows the PVC pipe installed into the perimeter drainage and is routed out of the crawl space:

Connect And Vent Through Walls Into Attic

Connect PVC pipe from crawl space(s) to top of PVC pipe installed in concrete floor and route this connection through walls in the above story(s) of the house and into the attic. The photo below shows the PVC pipe routed from the basement floor and two crawl spaces to the above story wall and into the attic:

Install Radon Fan And Exhaust Through Roof

Install Radon Fan at PVC pipe routed in attic and route fan exhaust through roof. The photo below shows the Radon Fan installed and exhausted through the roof: