Radon Resistant New Construction
Some homebuilders add construction elements to new homes that help make the homes radon-resistant. Some go so far as to install a full system with fan, even though building codes in most areas do not specifically require radon-resistant construction features. In some states, some homebuilders include radon-resistant construction elements as a value-added feature, or when requested by homebuyers.
There are advantages to installing a system when building a house:
The piping can be easily concealed in a chase;
The vent pipe can exit the roof and appear as a normal roof penetration;
The sub-grade can be prepared to make it easy to collect radon; and.
In many cases these systems work passively without need for fans.
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 and connected to a riser pipe.
The pipe riser should be routed through the interior of the building if possible, to allow the riser to be warmed, thus creating a natural stack effect. When this riser is combined with the gas-collecting system component installed below 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 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, because existing houses lack the specialized gas-collecting system component, such as perforated pipe, that is installed ony during new construction. Test the home to be sure it reduces the radon to levels you desire.
Ask your builder about radon resistant features; and if a system is installed.
See below for EPA publications with more information.