Preventive Measures: Existing Houses 

 

SUB-SLAB DEPRESSURIZATION

The most effective year-round radon reduction method usually used in Ohio is sub-slab depressurization or suction. Typical installation for a system in existing homes ranges from $600 to $2000. The air pressure in most homes is less than the air pressure in the surrounding soil. The difference in air pressures is what draws radon into the home. This method intercepts and expels the radon before it enters a building by creating a low pressure zone beneath the foundation. The radon is vented to the outside through pipes using a fan. This method also prevents soil-gas from entering the building by reversing the airflow direction: air will flow from the house into the soil, effectively sealing all remaining foundation cracks and holes. This method is appropriate for buildings with a basement or slab-on-grade foundation. For those having a crawl space or basement with an earthen floor, indoor radon can be reduced by increasing the ventilation above the floor with either natural or assisted air circulation through vents. Also for such buildings, a procedure called sub-membrane depressurization can be applied. Here a heavy plastic sheet is placed over the earthen floor and air is sucked out from the underlying ground and expelled to the outside. 

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MECHANICAL BARRIERS

The typical mechanical barriers that are suggested for radon control fit into one of the following two categories:
 

bullet Coatings: waterproofing or damp-proofing treatments are effective gas barriers for walls and joints.
bullet Membranes: membranes of plastic or rubber can be used to control liquid water penetration and water vapor diffusion, and thus are also effective as barriers to radon entry. The membranes could be used for sealing the unfinished crawl space of existing houses.

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PLANNED MECHANICAL SYSTEMS

The easiest way to reduce indoor radon is to increase the indoor/outdoor air exchange by opening windows, doors and vents in the lowest levels of a building. This is, of course, only practical during those months when heating or air conditioning is not used. Although there will be a reduction in radon levels when these are on the upwind side of the building, openings on the downwind side tend to increase radon levels.

Another short-term solution is to use a fan to blow air in to pressurize the house.

Other reduction methods are applicable to all building types. The least expensive is sealing cracks and pores in the floor and walls of basements, and floors above crawl spaces. This approach only reduces radon by at most 50 percent. Sealing is a favored treatment, however, when used in conjunction with sub-slab depressurization.  Another method, also of limited effectiveness, attempts to reverse the stack effect that pulls radon into a building by using fans to blow indoor air from the upper to the lower levels. Another method reduces radon by increasing the indoor/outdoor air exchange. This is accomplished with an air-to-air heat exchanger in a central heating and cooling system. Such a system uses heated or chilled air exhausted to the outside to warm or cool the incoming outdoor air. The principal reason heat exchangers are installed in buildings is to reduce energy costs but they have the added benefit of removing radon. In this latter capacity, however, they are only moderately effective. An alternative to a heat exchanger is a system that draws outside air, rather than air from inside as is normally done, into the cold-air return of a furnace.

WATER SUPPLY

Radon concentrations in Ohio's drinking water are generally low. If you are concerned about this, the radon in your water can be measured with any of the two special test devices available in the market. The first device is placed in the water reservoir of a toilet while the water is added to the second device to test radon concentration. Every 10,000 pCi/l of radon in the water contributes about 1 pCi/l of radon to the indoor air. Using this conversion factor, you can determine whether the radon level in your water is too high. In the unlikely event that a building's water supply is a significant source of indoor radon, the water should be purged of its radon before it enters the building. This can be done using an aeration system that mixes air with the water and then vents the air, and the radon along with it, to the outside. An alternative approach is to pass the water through a filter containing granular activated carbon. The radon will be adsorbed onto the carbon and so removed from the water. Although the filter will need to be replaced periodically, it has an advantage over the aeration system in that it also removes most of the other chemical contaminants that might be in the water.

These filters may become radioactively contaminated and so potentially expose people to excessive radiation doses. It may be illegal to dispose these filters as household garbage.
 

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