Construction Methods in Reducing Radon Risk in New Houses

Fazil T. Najafi
Win G. Li

DOI: 10.2190/XF3A-TNLN-6QEJ-X1NG


Radon is a radioactive gas that can be detrimental to human beings if there is constant exposure to high levels of concentration. Most radon gas comes from the soil and enters houses through concrete floor slabs. The State of Florida has developed draft standards for the construction of radon-resistant houses to control and prevent radon entering houses. Supporting research has been conducted by the University of Florida (UF) and other agencies. Its main purpose is to evaluate the performance and effectiveness of particular features of the standards. Radon problems have been studied in the health sciences for years; however, the construction industry has not yet given them serious attention.

There are two main approaches in reducing radon concentration in houses. The passive approach uses construction techniques to reduce the rate of radon entry. These techniques include installing vapor barriers underneath the floor slab, properly sealing plumbing penetrations and slab cracks, and installing radon mitigation systems in the house. When the passive approach does not reduce indoor radon concentrations to an acceptable level, the active approach can be applied, in which fans are used to lower the air pressure below the slab. These two mitigation methods were applied by UF in fourteen new houses in 1992 and twelve in 1993.

This article presents radon test results, and estimates construction costs, materials requirements, and the time required to install the systems. The constructability of the two methods and their overall effectiveness are also discussed.

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