WHAT TO DO
How to fix the problem
What can you do about radon? If a radon test indicates that levels in your house are too high, you can fix the problem. Houses can also be built in ways that reduce radon.
For basements or slab-on-grade foundations, the most reliable radon reduction method is active subslab suction, or subslab depressurization. Pipes are inserted through the floor slab into the crushed rock or soil underneath, or are inserted below the concrete slab from outside the house. Acting like a vacuum cleaner, a fan connected to the pipes draws the radon gas from below the house and releases it into the outdoor air. Passive subslab suction relies on air currents instead of a fan to draw up radon from below the house.
In houses with crawl spaces, radon levels can often be lowered by ventilating the crawlspace with or without the use of a fan.
Another effective method to reduce radon levels in crawl-space houses involves covering the earth floor with a heavy plastic sheet. A vent pipe draws the radon from under the sheet and vents it to the outdoors.
Basic radon-resistant construction:
A gas-permeable layer, such as a 4-inch layer of clean gravel, is placed beneath the slab or flooring system, allowing soil gas to move freely underneath the house.
Plastic sheeting placed on top of the gas-permeable layer and under the slab helps prevent soil gas from entering the home. In crawl spaces, the sheeting is placed directly over the crawl-space floor.
Sealing and caulking all below-grade openings in the foundation and walls reduces soil gas entry.
A vent pipe made of 3- or 4-inch PVC pipe (or other gas-tight pipe) runs from the gas-permeable layer through the house to the roof, venting radon and other soil gases to the outside.
An electrical junction box is included in the attic to make the wiring and installation of a vent fan easier. A separate junction box is placed in the living space to power the vent fan alarm.
Source: Sandra Fleishman, Washington Post