Radon mitigation system as installed, outside view (C) Daniel Friedman A Homeowner's Guide to Reducing Indoor Radon Gas or Radon in Water

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This article explains the impact of radon gas contamination levels in air or water on real estate sales and property values.

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Radon Mitigation Systems: How to Perform Radon Remediation to Remove Harmful Levels of Indoor Radon

Radon mitigation system - US EPA

As reported in Best Practices Guide to Residential Construction:

The EPA and the U.S. Geological Survey have rated every county in the United States as Zone 1 to 3 for radon risk. Links to state maps with county by- county risk levels can be found at radon/zonemap.html.

The EPA recommends that all homes in Zone 1 counties be built with radon-resistant features, which can be easily upgraded to a radon remediation system if needed.

Since homes in Zones 2 and 3 can also have high levels, it is best to check with your state radon office to see if they are aware of any local “hot spots.”

The techniques for radon-resistant building vary for different foundation types and site conditions, but all contain the six basic elements described below.

Following these steps creates a passive soil depressurization system, which sufficiently lowers radon levels in about 50% of homes requiring mitigation.

If radon levels need to be lowered further, the system can be easily converted to an active system by adding an inline fan, which can meet the target levels in nearly all cases (see Figure at above left, showing a typical radon mitigation system installation).

The goal of radon remediation is to lower the average indoor radon gas level to less than 4 pCi/L, and preferably 2 pCi/L.

Radon manometer (C) Daniel Friedman

A post mitigation radon test of 2 to 7 days should be done within 30 days of system installation. For an accurate reading, all windows and doors must be closed 12 hours before and during the test, except for normal use for entry and exit.

-- Adapted with permission from Best Practices Guide to Residential Construction.

Watch out: home ventilation systems, particularly powerful exhaust fans, can subvert a typical sub-slab suction type radion mitigation system by creating negative air pressures within the building. The radon system needs to be able to handle these pressure variations in the home.

See VENTILATION, BALANCED for an optimum approach to bringing in fresh outdoor air without increasing heating or cooling costs and without risking subverting the radon mitigation system.

Also see BACKDRAFTING HEATING EQUIPMENT for warnings about potentially fatal carbon monoxide hazards if exhaust fans cause back-drafting of heating appliance exhaust into the building.

US EPA Radon Zone Map For a Thorough Background in Radon Hazards, Radon Mitigation, & the History of Radon Concerns in the U.S. also see these articles reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.


Also see "Radon Basics", Q&A article, Solar Age, April 1984, includes advice for radon-resistant construction for an underground house built of concrete

This article series includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons.

Radon Gas Hazards Articles


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