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Radon Mitigation Questions & Answers

  • Are there other benefits to a Radon Mitigation system other than the removal of radon?

    An active radon reduction system reduces the entry into the home of radon, other soil gases and moisture, making the home healthier and reducing the likelihood of moisture-related new-home problems such as warping wood, odors and mold or mildew. After installing an active radon system, a certified radon mitigation contractor will provide a radon reduction guarantee. An active system:

    • Improves indoor air quality
    • Reduces radon, moisture, odor, allergens
    • Provides a more comfortable living environment
    • Adds more livable space
    • Preserves the building's structure
    • Protects interior fit and finish
  • Do RRNC and Passive Systems Reduce Radon?

    A passive system or RRNC might provide a small reduction in radon levels because of the natural convection of heat rising within the home, (stack effect), but an active system will reduce radon in nearly every new home. The risk to homeowners when they buy a home with RRNC or passive system is that both terms give the impression that a home is safe from radon. A home with RRNC or a passive radon system is a great step forward but not guaranteed to resist radon until activated with an inline fan.

    These two simple and relatively inexpensive additional steps will make a passive or RRNC system active:

    1. Add a radon fan.
    2. Test the radon level.

  • Are there special considerations for my home?
    • Homes built since the 1980s

    Frequently have a gravel bed under the concrete slabs, which creates a great opportunity for air flow. System design in these homes is almost exclusively aesthetics and the fan choice is a very energy efficient, lower suction fan.

    • Homes built before the 1970s

    Likely these have slabs poured directly onto soil, frequently compacted soil, or clay, which may lead to decreased air flow and special mitigation considerations. These special needs have a larger effect on system design and may benefit from the use of a high suction fan.

    • Slab areas greater than 2,000 + sq feet.

    These homes may require special design considerations, and system design may include or combine, larger piping, multiple penetrations or multiple systems. Fan selection is based upon both the pressure field extension and sub slab materials.

    • Multiple slab homes

    More often than not, proper mitigation will require addressing the whole building. If the home has more than one foundation type or level, (or crawl space) the system design may need to incorporate the full slab with additional pipe extensions into other slab areas.

  • What is the energy cost of running a mitigation system?

    Radon fans run continuously, however, with proper installation, design, and sealing of the basement slab. Most system's average energy cost should be less than $50 a year.

    We maximize energy efficiency by creating the best possible airflow under the slab, and by sealing basement floor cracks.

  • How much is a typical Radon mitigation system from St. Louis Radon?

    There are several factors that can affect the cost of a new radon mitigation system in the home. These might include the size of the home and the ground-contact area to be treated, the location of the system (exterior or garage installation) and other factors. The typical systems we install for the majority of homes we service range from between $785 to $1000, with most systems usually in the lower to middle-zone of that price spectrum. This compares to a national average cost of $1000 for sytems installed by other contractors around the country.

  • What increases the average cost of installing a radon system?

    If the home requires excessive sealing, larger more expensive fans, extra suction holes, the treatment of a crawl space, placement of the system inside walls or in attic spaces with roof penetrations, the price of the system can increase from the base price to reflect the extra cost of time and materials to install the system. Usually, treating crawl spaces brings the largest price change.

    Click here to review radon system photos that can increase the cost of installation.

  • Are Radon systems noisy?

    In most case, radon systems are barely audible, however design considerations may be necessary to limit noise transfer from the radon system into the interior for some of the higher air flow fans. If noise is a concern, please consult us about noise before making a decision on system design.

  • What about sealing my basement?

    "EPA does not recommend the use of sealing alone to reduce radon because by itself, sealing has not been shown to lower radon levels significantly or consistently."

    With this in mind, sealing areas that are open to soil exposure is still a component when reducing radon. Closing these barriers between the soil and living spaces help to create a vacuum under the home.

    Even with thorough efforts to seal these openings, substantial leakage can exist that is not visible to the eye. Over the years, new settlement cracks can also appear causing more leakage areas.

    Below are typical leakage areas and effective ways to seal these openings:

    Item Materials
    Sump Cover: Custom, non-breakable plastic disc with an air tight seal
    Accessible floor-wall joint: Polyurethane caulking
    Tiny "hair line" cracks: Typically not cost effective or meaningful
    Misc. cracks & openings: Polyurethane, expanding foam, mortar
    Drains: Air traps specific to the radon industry
    Open Earth: Poly sheeting placed over open earth and secured/sealed to walls
  • What about system maintenance?

    Most ASD, (active sub-slab depressurization), radon systems are virtually maintenance free. The only moving part is the fan and the system should maintain effectiveness for as long as the fan is running.

    Click to view the limted system maintenance issues with active sub-slab depressurization radon systems.



The first step to help ensure the safety of you and your family’s health and safety is to have your home tested for radon. At St. Louis Radon, our professional testers deploy the latest in computerized electronic real-time radon monitoring technology to provide you with a comprehensive report, including a complete visual graph of radon level data points as recorded over a 48-hour sampling period.

Learn More About Testing


If testing indicates levels of radon that require action, our team of engineers and technicians will design and install a custom radon mitigation system to safely and effectively redirect radon and other soil gasses out of your home. We also take additional measures to seal and close other possible breaches in the foundation that could let soil gasses into the through cracks or drain tiles systems.

Learn More About Mitigation

New Construction

With new home construction projects, it is crucial to determine the level of radon that may be present in the soil before the home is built. It’s also critical to have the new home retested for potential radon concentrations immediately following occupancy. We also highly recommend installing an Active Dampness Control System (ADC) with every new build.

Learn More About New Construction