A Homeowner’s Guide to Radon Resistant Construction

The presence of radon in a house is a serious health concern for homeowners and their families.In Pennsylvania, it is estimated that 40% of all home harbor an unsafe level of radon gas. In an attempt to address the dangers of living with radon, many newer homes are built to be “radon resistant” with a passive radon system. While these features can assist in lowering the radon in a home, one cannot assume that it is sufficient to maintain safe radon levels. A properly installed passive radon system can reduce the overall levels in the building by 50%. It is still very important to test a radon resistant home for the presence of radon.

What is Radon Resistant New Construction (RRNC)?

Radon resistant construction is a passive radon mitigation system that is installed during the home’s construction phase. Proper installation of a passive radon system begins before the foundation is poured. Loose aggregate with perimeter drain pipe and/or soil gascollection mat is laid in the foundation footprint. This will allow for air and gas to flow easily below the foundation and be pulled through the discharge stack. A vapor barrier is then installed on top of the aggregate to restrict the flow of gas upward through any foundations crac s.

Once the foundation is poured, PVC discharge piping is run through the center of the house from a stub in the foundation up to the attic and vented through the roof. Electrical access should be roughed into the attic near this vent pipe to allow for system activation if necessary.

Passive radon mitigation systems operate on a “chimney effect”. Air in the interior of the house is warmer than the air in the basement or below the foundation. As the warmer air in the discharge pipe rises it pulls air and radon gas from below the foundation out through the roof vent. A passive discharge stack located near an exterior wall of the house will be less effective than a centrally located system where the air is consistently warmer.

How Effective Are Radon Resistant (Passive Radon) Systems?

Properly installed passive radon systems do reduce overall radon levels. However, they may not reduce radon to an acceptable safe level if the concentrations of radon below the foundationare high. The effectiveness of the system depends on the ability of the air to flow through the sub-foundation aggregate, the strength of the chimney effect in the house and the existing radon concentration. The best expectation for the effectiveness of a passive system is a 50% reduction in radon concentration.

A fifty percent reduction rate is clearly adequate when ambient radon concentrations are low. It is VERY important that owners of homes with radon resistant features test to determine if radon levels are below 4.0 pCi/L (the EPA defined safe level). Radon resistant homes subject tohigh local concentrations of radon may not achieve sufficient reduction in radon levels to be considered safe.

Increasing the Effectiveness of Your Passive Radon System

It is not unusual for a radon resistant home to need additional mitigation. When radon levels test above 4.0 pCi/L, a homeowner should contact a certified radon mitigation contractor to discuss system activation. Radon system activation involves installing a radon fan to the discharge stack in the attic. This addition dramatically increases the effectiveness of the system. One of the attractive features of radon resistant construction is that this is a “hidden” system. The radon mitigation fan is located out of sight where it does not affect the exterior aesthetics of the home.


Many new homes today are built to be radon resistant. It is important to note that there are currently no regulations in Pennsylvania dictating how these systems are installed or mandating installation by a certified radon contractor. Therefore, the level of effectiveness varies widely. Properly installed passive radon systems can provide adequate radon mitigation but are not guaranteed to ensure safe radon levels. The only way to know if your home is sufficiently protected from radon gas is to perform a radon test. When necessary, passive radon systems can be easily and affordably activated to provide additional radon protection. The cost of passive system activation is less than the installation of a complete radon mitigationsystem.

About the Author

Katherine Fisher is the co-owner and Vice president of SWAT Environmental of Pennsylvania. She holds a Bachelor degree from Purdue University in Environmental Sciences and is NRPP certified in radon measurement and radon mitigation.

To purchase a radon test kit or to get a free quote on radon mitigation for your home, contact the experts at SWAT Environmental of Pennsylvania at 1-800-NO-RADON.

Our highly trained professional staff is here to provide you and your customers with the best in radon mitigation services including:

on 27 August 2015
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