John Banta was called to evaluate a home for radon. The owner had received a do-it-yourself radon test kit as a gift from relatives. When he finally got around to performing the test, he could not believe the laboratory results. His daughter’s room registered 24 picocuries, six times higher than the EPA’s recommended action level. John’s electronic radon equipment confirmed the test results.
John proposed a radon reduction technique called subslab suction. It involved sucking radon from under the slab and ventilating it to the outside. Holes would be drilled in the downstairs slab so that pipes could be inserted and connected to an exhaust fan, a method frequently used in unfinished basements. Since the owner had just finished installing an expensive marble floor downstairs, he was not willing to accept this proposal.
After some thought, John suggested that the subslab suction technique be modified so that the drilling would take place horizontally under the slab through the outside of the hill on which the first floor rested. A company that drills horizontal wells was contracted for the job. The site was surveyed and the drill set to bore just under the foundation. Six evenly spaced holes were bored horizontally all the way under the house. After the drill was withdrawn from each hole, a perforated pipe was inserted to provide a pathway for gas from radon-contaminated soil to be sucked from under the home. The owner finished the job by
aggregate through the center of the envelope. The pipe is connected to an unperforated riser tube that vents to the outside. The vent tube acts as a passive radon removal outlet.
If radon levels are still unacceptable once the building is completed, a fan can be attached to the vent pipe to actively suction out the gas.
Method 2: In place of aggregate and perforated pipe, Soil Gas Collector Matting can be laid on the finished grade prior to pouring concrete. The matting, which is covered in filter fabric, is laid around the inside perimeter of the foundation in a swath about one foot wide, and the concrete is poured directly on top. The matting is connected to a vertical riser vent that extends through the roof. The natural chimney effect will draw the soil gas upward. If deemed necessary, the system can be adapted for active suction with the addition of a fan once the building is enclosed. In areas with high water tables, consult a geotechnical engineer about proper drainage prior to installing any soil gas removal system.
Products for Soil Gas Control
The following low-emission products may be used to block entry of radon from the ground into the living space:
• AFM Safecoat DynoSeal: Water-, vapor-, and moisture-proof membrane sealer
• Cross Tuff: Specify radon-control grade
• Tu-Tuf4: Crosslinked polyethylene sheeting
Water Management at Doors and Windows
Door and window openings that are improp — joining all the perforated pipes together with solid pipe. At a short distance from the home he connected an exhaust fan to the pipe to suck radon to the outside, where it dissipated. The pipes were then covered with soil and the area landscaped. The radon in the home was reduced to an acceptable level of approximately one picocurie. If the fan is shut off, however, the radon level will begin to climb. More radon testing was carried out on other buildings located on the property and in the general neighborhood. No other elevated radon levels were found.
Discussion
Radon can exist in isolated spots, depending on underlying geological formations. Some parts of
erly detailed are a common source of water intrusion in homes. Often these leaks go undetected until they have caused severe damage when water finds a path directly into the wall cavity without ever revealing damp surfaces visible from within the home.
Until recently, all products for door and window flashing were asphalt-based. The following flexible flashing products do not contain asphalt:
• Tyvek Flex Wrap: Self-sealing, 70-mil elas — ticized polyethylene film laminate with a synthetic rubber adhesive for windowsills, round top and custom shaped windows, 3D sill projections, and wall interruptions
• Tyvek StraightFlash: Self-sealing, 30-mil polyethylene film laminate with a synthetic rubber adhesive for jambs and heads of rectangular shaped windows
the US are known to have higher radon levels than others. Homes with basements, cellars, or other subterranean structures are the most susceptible to radon accumulation. Yet even homes with slab foundations and ventilated crawl spaces can have elevated levels. The only way to be certain is through radon testing. In John’s experience, radon can almost always be reduced to acceptable levels. When building your home, use appropriate techniques to avoid the possibility of radon accumulation if radon is known to be present in your area.
• VaproFlashing: Non-self-sealing bonded polypropylene fabric flashing, requiring the use of VaproAdhesive to adhere to most building materials (refer to Vapro- Shield)
• WindowWrap-Butyl: Self-sealing 20-mil laminated polyethylene film with butyl rubber adhesive for flashing window and door openings and building joints
