Passive radon mitigation systems
Passive radon mitigation systems can save lives. When properly installed, passive radon mitigation systems can keep radon levels down without the assistance of a radon fan. New construction homes can be built radon resistant with a permanently installed passive radon system.
Although codes vary from town to town, there are six basic components of radon resistant new construction techniques:
- Install a gas permeable layer before the concrete slab is poured. This is usually a 6" layer of clean gravel. Gravel is very porous and allows for simple air movement below the concrete slab. This will help the passive radon system move the radon and other soil gas without restriction.
- Install a vapor barrier above the gas permeable layer before the concrete slab is poured. A minimum 6mil plastic membrane is recommended. At RadoVent™ we overlap all seams in plastic by at least 12" and tape the seams with high grade vinyl tape. RadoVent™ now uses a 10mil true vapor barrier that is superior to the minimum 6mil visqueen.
- install radon collection point with schedule #40 PVC pipe stub. Concrete to be poured around this pipe stub. It is extremely important to create a radon collection point that will not be impaired when concrete is poured. This is usually done by installing a soil gas collection pipe (drain-tile) or PVC tee.
- Seal and caulk radon entry points. After It is important to seal all visible cracks in the concrete floor, control joints and cold joints (where the foundation meets the floor) using proper concrete caulk. If the home has a sump, it is a primary radon entry point and should be sealed air tight with a proper sump cover. The sump cover should be removable in the event the sump needs to be worked on. Plumbing roughs are another radon entry point that should be sealed with a cover. Once plumbing work is complete it is important to seal around the pipes with concrete or expandable foam sealant.
- Install the radon vent pipe. When installing a passive radon system, it is important to install the radon vent pipe through an interior wall or flue chase. As the home warms the pipe, a natural stack effect will occur to pull air through the pipe which in-turn pulls the radon gas out of the soil. It is best practice to use 4" PVC in radon resistant new construction to allow for maximum CFM in the event the system is activated. The radon suction pipe should continue through interior walls to the attic space above the home or building in a location that will allow for future access. The vent stack should terminate through the roof at least ten feet from windows, doors or other openings to the building.
- Install a electrical junction box within reachable distance of the radon vent pipe in the attic. This will allow for an electrical source in the event the system is activated.
It is important to use a radon mitigation contractor when using radon resistant new construction techniques. Radon contractors know how to properly move the air below the building. In many areas, plumbers are used to install passive radon systems. Often we have found that the suction point is placed in the gravel and the concrete has created a seal around the radon suction point location. This is dangerous because the homeowner is under the impression that the home is built radon resistant yet the passive radon pipe cannot move any air. If you have a home with a passive system, be certain to perform a radon test at least every two years.
In the event radon levels remain elevated with after radon resistant techniques have been used, the passive radon system can easily be converted to an active soil depressurization system (active radon system). This can be done by adding a radon fan to the radon vent pipe in the attic space above the home or building.