Radon Mitigation - Radon Removal

Radon removal is implemented to reduce indoor radon levels. Radon can be removed by the use of air pipes and fans to exhaust sub-slab air to the outside called sub-slab depressurization, active soil depressurization, or soil suction.

For crawlspaces, the EPA states “An effective method to reduce radon levels in crawlspace homes involves covering the earth floor with a high-density plastic sheet. A vent pipe and fan are used to draw the radon from under the sheet and vent it to the outdoors. This form of soil suction is called submembrane suction, and when properly applied is the most effective way to reduce radon levels in crawlspace homes.”

The most common approaches are active soil depressurization (ASD) and mechanical ventilation (MV). Experience has shown that ASD is applicable to most buildings since radon usually enters from the soil and rock underneath and MV is used when the indoor radon is emitted from the building materials. A less common approach works efficiently by reducing air pressures within cavities of exterior and demising walls where radon emitting from building materials, most often concrete blocks, collects.

Nearly all mechanical ventilation-based radon control systems are of fixed rate operation, and even if the indoor relative humidity in the interior of a building goes high, they will continue to inject moisture-laden air into this wet environment increasing the likelihood of mold growth. This is especially risky in hot, humid climates. It is not an unusual practice for radon mitigators in hot, humid climates to warn of possible resulting mold problems by way of an easily removed warning sticker.

Above Slab Air Pressure Differential Barrier technology ASAPDB requires that the interior pressure envelope, most often drywall, as well as all ductwork for air conditioning systems, be made as airtight as possible. A small blower, often no more than 15 cubic feet per minute may then extract the radon-laden air from these cavities and exhaust it to the out of doors. With well-sealed HVAC ducts, very small negative pressures, perhaps as little as 0.5 pascal, will prevent the entry of highly radon-laden wall cavity air from entering into the breathing zone. Such ASAPDB technology is often the best radon mitigation choice for high rise condominiums as it does not increase indoor humidity loads in hot humid climates, and it can also work well to prevent mold growth in exterior walls in heating climates.