Radon is a slow, silent killer. In fact, it’s the leading cause of lung cancer in non-smokers. When a homeowner suspected his home might have a radon issue, he called the experts at Ask This Old House. Building engineer Ross Trethewey knew how to keep the homeowner and his dog safe despite high levels of radon in the basement, calling on the help of radon mitigation technician Chris Lebreton.
Since the radon mitigation system was installed, the homeowner has reported his continuous radon monitor has been reading an average level of 0.7pCi/l.
Well below the 12.7pCi/l average he had when Ross first arrived.
Naturally Occurring but Very Dangerous
Radon is a naturally occurring radioactive gas. It’s a byproduct of uranium breakdown in rocks and soil underground. As radon gas rises, it looks for the easiest route to escape, and that’s often through basement and foundation floors and walls, pipe penetrations, or even drains and pump basins.
Radon is very dangerous to humans. It’s invisible and odorless but can exist in high-enough concentrations to cause long-term health issues. In fact, radon is the number one cause of lung cancer in non-smokers.
Monitoring is Key
The only way to test for radon is to monitor it. Radon detection devices that track radon levels over a longer period of time will help homeowners determine if there is a radon issue. Described in pCi/L, or picocuries per liter, the EPA recommends an average reading of four or less. Homes with higher averages should seek mitigation measures.
Continuous monitoring is a much better baseline than simply taking spot readings. Radon levels in a home can fluctuate considerably throughout the day, depending on many factors such as precipitation, exhaust fans, outside temperatures, and more. Safe levels in the morning may become elevated at other points throughout the day, so continuous monitoring is a must.
The Solution? Sub-Slab Depressurization
In most cases, the solution to a radon issue is a depressurization system. These systems actively pull radon gases up from the soil underneath the home and push them outside where they safely dissipate. Built from specialized fans and PVC pipes, these systems act like a drinking straw from below the home’s foundation, pulling radon out of the soil before it can enter the home.
How Sub-Slab Depressurization Works
Radon systems should be installed by experts to ensure they’re working properly, and the home is safe. But it’s helpful to understand how these systems are installed and what they do:
First, a technician will survey the basement to find any potential cracks or leakage areas through which radon could enter the home. Any areas are sealed with mortar to prevent leaks.
Grab samplers are installed around the basement. These systems work together to track the flow of radon throughout the basement. This helps the technician determine the best location for the mitigation system.
A 4.5-inch hole is drilled in the area of highest concentration, and smaller holes are drilled in the other corners. The 4.5-inch hole will serve as the penetration point for the radon system but also allow the technician to create suction with a shop vac to check airflow at the other holes.
Theatrical smoke is used near the smaller holes while a shop vac creates suction. If the smoke is pulled into the holes, there is an air pathway, ensuring that a fan at the larger hole will pull radon from the corners as well. The smaller holes are all filled when finished.
Debris and soil is removed from the 4.5-inch hole to ensure there is a proper sump for the mitigation system to draw from.
A series of fittings and sealants is used to transition from the 4.5-inch hole to a 3-inch pipe that runs up from the basement and out of the house.
A fan is installed on the outside of the home, with additional piping installed to release the radon above the roof line.
Electricity is then run to the fan, with a weatherproof on-off switch installed nearby.
A monometer is installed in the basement to show that the fan is working, and an additional alarm is installed to alert if the radon levels get too high.
The fan itself should last about 10 years, but it’s important to test radon levels every couple of years to ensure things are still working properly. A continuous monitoring system is an ideal solution.
Resources
Expert assistance provided by: Walter Irwin Radon Mitigation & Testing
Testing: Check with your state to see if they offer free radon tests.
American Lung Association low-cost, short-term radon tests
Long-term radon monitors – Ecosense
Mitigation Companies: When hiring radon testing and mitigation experts, make sure they are certified by one of the following organizations:
The National Radon Safety Board (NRSB)
Additional Information: AARST standards for every building type
