Passive Systems See our New Construction page. Radon levels can often be lowered simply by increasing the amount of fresh air in a given area.
Active Systems • Sub-Slab Depressurization Negative pressure is created in the soil beneath a structure, using a continuously running inline exhaust fan and venting system which prevents radon from entering a building, releasing it above the roofline.
• Sub-Membrane Depressurization Exposed soil in a crawl space is covered by vapor barrier sheeting. Radon is drawn from under the vapor barrier and released above the roofline via a fan-driven venting system.
In Water • Radon is a gas and, like oxygen, may be absorbed into water. • Elevated levels in water are typically associated with well water, not domestic water supplies. • Radon can be released (via out-gassing) during showers, laundry washing, etc. • It takes 10,000 pCi/L of radon in water to out-gas as 1 pCi/L of radon in the air. • Mitigation is usually accomplished by installing an aeration system to address the incoming water supply line to a building.
HRV: Heat Recovery Ventilation Systems
This method works by dilution, venting heated, stale indoor air to the exterior, while drawing in fresh outdoor air. Before reaching the outside, the heat from the stale indoor air is captured by a radiator-like assembly, transferred to the cooler incoming fresh air. This dilutes, to some degree, the amount of radon in a building.
• Does not prevent radon from entering a building.
• Typically costs more than other mitigation techniques.
• Difficult to attain consistent and sufficient radon reduction. Filters
Air filters, by themselves, usually do a poor job of removing radon. Sealing
• It is virtually impossible to seal 100% of any flooring area and, since radon is a gas, it can move through the smallest cracks and gaps that may have been missed in any sealing process.
• Concrete shrinks and expands over time, as do most underlying soils. This leads to cracking that can compromise any sealing that has been done.
• Most soils under buildings is “expansive,” meaning it expands and contracts depending upon moisture content: expanding during the wet season, contracting during drier weather.
• This leads to further cracking, further compromising any sealing that has been done.
• Sealing radon out is considered a short-term, non-permanent measure. Post-Mitigation Testing
The only way to know a mitigation system is effective is to test the home. A property owner should always do a short-term radon test immediately after a mitigation system has been installed. Cascade Radon conducts such testing after each system installation. It is also recommended a homeowner conduct periodic long-term testing every year or two to verify system performance.