By Kenn Garder, National Accounts Manager and Technical Support, NPI/GPI
Radon is a naturally occurring radioactive gas produced by the breakdown of uranium in soil, rock and water. Because air pressure inside a house is usually lower than pressure in the soil around the foundation, a house acts as a vacuum, drawing radon in through foundation cracks and other openings. Once inside the house, radon gas is diluted somewhat by fresh air that is naturally pulled in around windows and doors. The radon gas is then distributed throughout the house by the heating and cooling system. When a house is tested for radon and elevated radon levels — 4 picocuries per liter (pCi/l) or higher — are discovered, the EPA recommends a radon mitigation system be installed.
Reliable techniques are available to reduce radon in houses. Research conducted by public and private agencies has formed a strong knowledge base of proven mitigation systems for homes, schools and commercial buildings.
Design of a radon mitigation system is determined by the construction of the house, not the concentration of radon in the house. A state or nationally qualified contractor should be hired to design and install the system in accordance with the local, state or national standards used in the area where the house is located.
Radon mitigation or reduction requires more than just sealing cracks in the foundation. Active soil depressurization has proven to be cost-effective and reliable for reducing radon gas in a building. A depressurization system draws air and radon gas from beneath the foundation and exhausts it outside the building. The termination point of the exhaust should be far enough away from windows and door openings so it will not re-enter. A common design for the system is a plastic pipe connected to the soil through a hole in a slab floor, through a sump lid connection, or beneath a plastic sheet in a crawl space. Attached to the pipe is a quiet, continuously operating fan that discharges the radon outdoors.
Additional parts of a house or building may need special attention when designing the radon mitigation system:
- If the return-air ductwork for a forced-air HVAC system is located beneath a concrete slab floor, then the vacuum created by the blower fan can pull radon into the system if the duct is not sealed.
- Soil air drawn from beneath a floor or in a crawl space is commonly high in moisture. If the system is not designed and installed properly, this moisture will condense and pool inside the ventilation pipe.
- Local building codes may require the piping for a radon mitigation system be installed during construction of the house to allow for future mitigation needs.
The cost to install a radon mitigation system can range from $800 to $1,500, with a national average of $1,200. For more information about radon and mitigation systems, visit the Environmental Protection Agency (EPA) website in the United States, or visit the Health Canada website in Canada.