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An effective technique to achieve radon resistance in buildings is through sealing its routes into them.The method is briefly described in this article.

Floor sealing against radon
Because the greatest source of indoor radon is almost always radon-containing soil gas that enters the building through cracks and openings in the slab and substructure.A good place to begin when building a radon resistant building is to make the slab and substructure as radon-resistant as economically feasible.

However, it is difficult, if not impossible, to seal every crack and penetration. Therefore, sealing radon entry routes and constructing physical barriers as a stand-alone approach for radon control in schools and other large buildings, is not currently recommended. On the other hand, sealing of major radon entry routes will help reduce radon levels and will also greatly increase the effectiveness of other radon prevention techniques. For example, sealing increases the effectiveness of Active Soil Depressurization (ASD) by improving the pressure field extension beneath the slab. Sealing also helps to achieve building pressurization by ensuring that the building is a “tight box” without air leakage. Many of these sealing techniques are standard good construction practices.

Sealing Recommendations

Radon entry routes that should be sealed are:

  • Floor/wall crack and other expansion joints. Where code permits, replace expansion joints with pour joints and/or control saw joints because they are more easily and effectively sealed.
  • Areas around all piping systems that penetrate the slab or foundation walls below grade( utility trenches,electrical conduits,plumbing penetrations, etc)
  • Masonry basement walls.
Limitations of Sealing

Many construction materials are effective air and water barriers and also retard the transfer of radon containing soil gas. In practice however, the difficulties that arise when using sealing and physical barrier techniques as the only means of control are virtually insurmountable. Physical barriers have proven to be frequently damaged during installation; more over, failure to seal a single opening can negate the entire effort, especially when radon concentrations are high. Nevertheless, sealing of radon entry routes in a building should be done: not only will sealing retard radon transfer but sealing will also increase the effectiveness of ASD and building pressurization.

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