This figure illustrates the basic concept of a typical "soil depressurization" radon control system installed during the construction of a home.
These systems draw radon and other soil gases from beneath the floor and upward through a pipe that exits above the roof. Soil air travels readily through the layer of gravel or sand that usually forms the base for a concrete slab.
Other options include a soil-gas collection system consisting of a loop of perforated plastic pipe buried inside the foundation footing, or a loop of gas-permeable matting laid on the sub-grade material directly under the slab, connected to a riser pipe.
The pipe riser should be routed through the interior of the building to allow the riser to be warmed, thus creating a natural stack effect. When this riser is combined with the gas collecting system installed beneath the slab, it can draw significant amounts of radon from beneath the home. The performance of this natural convection system is enhanced by sealing openings in the slab and walls so the air drawn up through the system comes from beneath the building rather than from within the building.
The efficiency of these passive systems is further enhanced when the riser pipe is routed through the warmest spaces in the home such as the wall-cavity plumbing chase where the furnace and/or hot water flues are located. The radon vent should be dedicated only to the radon reduction system and must not be connected to any combustion flues. Allowance is always made for adding a suction fan to the vent pipe, usually in the attic area, if needed later to increase system capabilities.
This passive-system approach is usually not chosen for retrofit mitigation of homes, since existing houses lack the specialized gas-collecting system component, such as perforated pipe, that is installed only during new construction.
Ask your builder about radon resistant features.
If a system is installed.
Test the home to be sure it reduces the radon to levels you desire.
Click here for the "Builing Radon Out - A Step-by-Step Guide On How To Build Radon Resistant Homes" guide provided by the United States Enviromental Protection Agency - Office of Air and Radiation.
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