Sub-slab depressurization is the most common and effective radon mitigation method used to reduce radon levels in homes with concrete slab foundations. The system is installed by cutting a hole in the slab and removing approximately 10 gallons of material beneath the concrete to create a suction pit. A PVC pipe is then inserted and sealed to the slab, and a radon mitigation fan draws radon-laden soil gases from beneath the foundation and safely vents them above the roofline.

Proper sealing of the slab, cracks, and foundation penetrations is an important part of the system, as it helps expand the negative pressure field beneath the slab and improves the overall performance and efficiency of the radon mitigation system.

A combination radon mitigation system is used in homes that have both a basement slab and a crawlspace. This type of system combines sub-slab depressurization and sub-membrane radon mitigation to effectively reduce radon levels from multiple foundation areas.

A radon-resistant vapor barrier is installed over the crawlspace soil and sealed to the foundation walls and penetrations. A suction point is placed beneath the membrane, and the crawlspace suction is connected to the sub-slab depressurization system. A single radon mitigation fan then creates negative pressure beneath both the concrete slab and the crawlspace barrier.

This combined radon mitigation approach helps capture radon gas from beneath the slab and crawlspace soil and safely vent it above the roofline, improving the overall effectiveness of the radon reduction system.

Sump pit radon mitigation works by connecting a PVC suction pipe to the sump pit, allowing a radon mitigation fan to draw soil gases from beneath the foundation and safely vent them above the roofline. Because the sump pit often connects directly to the drainage system beneath the slab, it can be one of the most effective locations for creating suction in a radon mitigation system.

The system is typically attached directly to the sump pit basin or, in some newer homes, to a window well drain that is plumbed into the sump system. The sump pit is then properly sealed, which allows the system to create negative pressure beneath the slab and prevent radon gas from entering the home.

Some homes are built with passive radon mitigation systems installed during construction. These systems typically consist of PVC piping that runs from beneath the slab, through the home, and vents above the roofline. Passive systems rely on the stack effect, where warm air rising through the home naturally pulls radon gas from beneath the foundation and vents it outside.

While passive radon systems can help reduce radon levels, they do not always maintain levels below the EPA recommended action level of 4.0 pCi/L. If testing shows elevated radon levels, the passive system can usually be upgraded to an active radon mitigation system by adding a radon fan, typically installed in the attic. The fan actively draws radon gas from beneath the slab, significantly improving the effectiveness of the radon reduction system.

Sub-membrane radon mitigation is commonly used in homes with crawlspaces that have exposed soil floors. This method involves covering the crawlspace floor with a durable radon-resistant vapor barrier that is carefully sealed to the foundation walls, piers, and around all penetrations to isolate the soil from the home.

A PVC suction pipe is installed beneath the membrane, and a radon mitigation fan creates negative pressure under the barrier, capturing radon gas before it can enter the living space. The collected soil gases are then vented safely above the roofline through the radon mitigation system.

This approach effectively isolates the crawlspace soil and reduces radon levels inside the home while also helping control moisture and soil gases.

Some homes have crawlspaces that are too small or inaccessible for installing a vapor barrier or sub-membrane radon mitigation system. In these situations, crawlspace depressurization may be used as an alternative radon reduction method.

This system works by using a radon mitigation fan to move air through the crawlspace, drawing radon gases away from the home and venting them safely outside. By improving airflow and reducing radon concentration beneath the living space, crawlspace depressurization can help lower indoor radon levels and improve overall indoor air quality.