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Radon Mitigation

A Radon Test Showed Elevated Levels - NOW what?

   If your home has been tested for radon, and the test showed elevated levels, you're asking "so now what do I do?". Radon mitigation can be pricey, and you shouldn't jump to premature conclusions.
   First, take a look at the levels that were detected. If the reading was between 4.0 and 8.0 pCi/L, you should do a follow up test to be sure that the first test was accurate. Test results can be corrupted in any number of ways - a test that doesn't follow protocol, tampering, etc. Stranger things have happened. If the first test shows radon levels beyond 8.0 pCi/L, you should consider radon mitigation at this point, is always a good idea.
   Inexpensive radon testing kits are available at RTCA and Pro-Lab.
   Re-test the home with your choice of measurement devices to re-evaluate the results. If the test still shows elevated levels of radon in the home (beyond 4.0 pCi/L) then you should take steps to reduce radon levels.
   If the home is being tested as part of a real estate transaction, be sure to use a third party (like a certified home inspector or radon measurement specialist) to avoid any conflict of interest.

Radon Mitigation - Getting Started

   There are several ways to reduce radon levels in the home, and we'll address each one, including the professional installation of a radon mitigation system. In the event that both test results showed radon levels above 4.0 pCi/L, which is the EPA "action level", then by all means you should take steps to reduce it. Radon levels can be reduced passively or actively, and each method carries a varying level of effectiveness and of course, a different price tag.

Sub-Slab Radon Mitigation Systems

   Perhaps the most effective method of radon reduction is the sub-slab radon mitigation system. This system is sometimes referred to as sub-slab depressurization, because it reduces the upward pressure from radon gas into the basement. Some newer homes in areas of high radon levels are pre-fitted with sub-slab mitigation systems during construction, which is the most effective (and cost effective) way to keep radon levels in check. Costs for this type of system are generally higher if the home has to be retro-fitted after construction.
   The slab (basement floor) is penetrated in a number of places and pits are hollowed beneath the floor. The pits are connected using a network of PVC piping using flexible couplings. One end of the PVC network is connected to a fan, which moves air through the PVC piping, and the other end is vented to the outdoors, usually through the roof. The PVC is routed to the roof via plumbing chases or closets where it will not be an eyesore. The system intercepts radon gas where it enters the home and safely expels it above the roof line.
   Some of these radon mitigation systems utilize a constant air flow through the piping, and some use a level-detection system to activate the fan.
   Depending upon the size and extent of the installed system, costs for profession installation of a sub-slab depressurization system may run from $800 to upwards of $4500.

Passive Radon Reduction

   Passive radon reduction is much less effective the other methods, and is considered a temporary solution to a permanent problem. Passive reduction involves opening windows, doors and supplying ventilation to move the radon gas from the living area to the outdoors.
   Sealing cracks and openings in the basement floor and walls is another example of passive radon reduction. While sealing the building envelope against radon is a good idea, it is not recommended as a total solution to high radon levels.
   Passive radon reduction is only recommended if radon levels are found to be below the EPA action level of 4.0 pCi/L. After doors and windows are closed, radon levels will usually return to the previous level within 12 hours. For this reason, passive radon reduction methods are not recommended as a long-term solution to elevated radon levels.

Radon Mitigation in Crawl Spaces

   Radon levels can be reduced in a crawl space of a home in several ways - again, using active and passive reduction methods.
   First, passive methods.
   Crawl spaces normally have an exposed soil floor or a poured concrete floor. One passive method of radon reduction involves laying plastic sheeting on the floor to prevent radon gas from migrating upward from the ground. The plastic sheeting should be secured and sealed to the walls of the crawl space to prevent radon from moving to the perimeter of the sheeting and entering the crawl space near the edges. The use of plastic sheeting on exposed soil floors can also help to prevent moisture and mold problems in the crawl space.
    Another passive radon reduction method is to provide air flow through the crawl space to the outdoors by opening or installing vents on either end of the crawl space. The passive air flow carries the radon gas from the crawl space to the outdoors, but since crawl spaces are at or near ground level, the radon is not expelled to the optimal location (away from human activity). Vent openings should be extented upward at least 10 feet to route the expelled radon gas away from ground level where people may be exposed to it's effects.
   Both of these passive methods are effective in reducing radon levels to some extent.
   Active radon reduction in crawl spaces is more effective than passive methods, and involves actively moving air through the crawl space to push the radon gas out. Fans are installed in one end of the crawl space and vents are opened (or installed) in the opposite end to provide a constant air flow through the area.  Any radon entering the crawl space is pushed out through the open vents.
   Another active radon reduction method uses the plastic sheeting over the floor, and a fan system to ventilate the area between the floor and the sheeting. This method captures the radon gas as it migrates through the soil into the crawl space, and immediately moves it to the outdoors before it enters the living space. This is considered the most effective way of controlling radon in a crawl space.
   Note: If the active ventilation (fan) methods are implemented in colder climates, any plumbing pipes and floors should be well-insulated to prevent freezing of pipes and chilly floors. 


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