The US EPA recommends that you should mitigate if your radon test reads 4 pCi/L or higher, and consider radon mitigation if your radon level is above 2 pCi/L. But there is no "safe level" of radon - you should strive to reduce this radioactive gas to a minimum. There are a few radon reduction methods available:
|Comparison of Radon Mitigation Methods|
|Method||Typical Radon Reduction||Typical installation costs (contractor)||Typical operating costs for fan electricity and energy loss in heated/cooled air (annual)||Comments|
|Fan-based mitigation system (sub-slab depressurization)||80%-99%||$800-2,500||$75-175||Works best if air can move easily under the slab - a gravel bed. Recommended by the US EPA.|
|Drain-tile suction with a fan||90%-99%||$800-1,700||$75-175||Works best if drain tiles form a complete loop around the basement.|
|Block-wall suction with a fan||50%-99%||$1,500-3,000||$150-300||Only in basements with hollow block walls, requires sealing of all openings.|
|Sump hole suction with a fan||90%-99%||$800-2,500||$100-225||Works best if air can move easily under slab to the sump and if drain tiles form complete loop.|
|Caulking of radon entry routes||0%-50%||$100-600||$0||Ignores radon infiltration through concrete. Normally used in combination with other techniques.|
|Basement pressurization||50%-99%||$500-1,500||$150-500||Requires tight basements that can be isolated from outdoors and upper floors. Unpredictable results.|
|Natural ventilation through windows or vents||Variable||$200-500 if additional vents are installed||$100-700||High loss in heated or conditioned air; operating costs depend on the ventilation and utility rates. Unpredictable results.|
|Basement ventilation fan with heat recovery||25%-50% if used for full house; 25%-75% if used for the basement||$1,200-2,500||$75-500 for continuous operation||Reduces energy losses in heated/conditioned air. Works best in a tight house. May cause back-drafting.|
|RadonSeal deep-penetrating concrete sealer||80%-95%||$400-$600||$0||A quick and safe application.|
Considering the savings on installation and operation, RadonSeal will save the average homeowner $2,300 over ten years. See Radon Mitigation Savings.
If your basement is still unfinished and unpainted, RadonSeal makes radon mitigation quick and easy. There are just two basic steps. Products you may need:
RadonSeal makes radon mitigation very affordable. The spray-on application with a hand-pump garden sprayer is quick and easy. And safe. RadonSeal is a waterborne sealer, non-toxic, nonflammable, with zero VOCs. You have no reason to procrastinate!
The RadonSeal seal is PERMANENT – no re-application is ever needed. Unlike surface sealers or waterproofing paints, RadonSeal cannot peel or wear off. It cannot be pushed out by hydrostatic pressure. Follow the instructions and you will reduce the radon level below the EPA Action Limit of 4 pCi/L – backed up by a Limited Lifetime Money-Back Guarantee!
With RadonSeal, most homeowners reduce radon to the 1 - 2 pCi/L range. The theoretical bottom limit is the natural level of radon in ambient air, which averages 0.45 pCi/L in the U.S. but exceeds 1 pCi/L in some areas.
Feedback from Customers
...our basement now is reading 2.0, checked at 2 different locations. Not bad for starting at 29 pCi/L! ...
... a concrete floor and cinder block walls in my basement. I used 3 pails of Radonseal, primarily because the cinder block is so porous ...I dropped the radon reading from 18 to 0.7.
... The reading was twice the recommended safety level (8.2 pCi/L) prior to applying the seal. We applied the seal, installed an electronic permanent tester and the radon reading is now 0.2! ...
...house with radon level of 64 pCi, prior owner will not reduce or correct. In Pennsylvania (South Central). ... After RadonSeal, I saw a drop in Radon (using 72 hour electronic monitor) from 64 pCi to 2 pCi! Of course I did seal all cracks with a polyurethane made for expansion joints and cap the sump pump. ....
See more Testimonials
The Consumer's Guide from EPA: "Minimize the effect of installing a radon reduction system in your house by assuring that it blends with its surroundings. For instance: radon vent pipes may be encased with materials that match the exterior of your house, or the pipes may be routed indoors up through closets. Suction systems require that one or more holes be drilled through the basement floor, preferably in a central location. The piping will likely constrain your ideas on finishing the basement."
RadonSeal eliminates the problems of unsightly piping and lost space. It does not change the color or surface of the concrete. There is no annoying hum of a radon fan on balmy summer nights.
Radon fans and piping tend to raise concern in potential home buyers, who may have never heard that there is a radioactive gas called radon. Real estate agents agree that fan mitigation systems significantly reduce the market value of the house.
RadonSeal works invisibly inside the concrete.
If you install a mechanical radon mitigation system, the basement and the concrete will still need additional care and expenses like waterproofing, repair, preservation, preparation for painting or floor tiles. RadonSeal does much more than radon mitigation. It also stops or prevents water seepage, water vapor migration, condensation, molds, mildew, and musty odors. It strengthens and preserves the concrete, stops efflorescence and concrete dusting, and prepares the concrete for painting or adhesives.
Applying RadonSeal will reduce the indoor radon level further, will decrease the energy loss in conditioned indoor air drawn through concrete to the fan, and will act as a backup if the fan fails or during power outages.
Getting a fan radon mitigation installed is likely the best and easiest solution for fully finished basements. You can find duly certified radon mitigation contractors in Yellow Pages.
Sealing only the floor with RadonSeal may be sufficient. Much more radon tends to penetrate through the slab than through the walls, because radon gas is trapped underneath between the footings. Although the result cannot be guaranteed, many homeowners are successful by lifting the carpet or linoleum and sealing just the floor.
If the basement floor or slab is painted or covered with floor tiles, removing the paint or tiles and adhesive is a tedious job. See more tips at FAQ.
EPA: "The average house costs about $1,200 for a contractor to fix, although this can range from about $800 to about $2,500, depending on the characteristics of the house and the method used."
RadonSeal can save you hundreds of dollars - the typical cost is only $400-$600.
EPA: "Systems that use fans are more effective in reducing radon levels; however, they will increase your electric bill. Remember, the fan should never be turned off; it must run continuously for the system to work correctly. A warning device must be installed to alert you if the system stops working properly."
RadonSeal has zero operating costs and is not subject to mechanical breakdowns or grid failures. If you already have a fan radon mitigation system, apply RadonSeal as a back-up.
EPA: "Most types of radon reduction systems cause some loss of heated or air conditioned air, which could increase your utility bills. How much your utility bills will be affected depends on the climate you live in, what kind of reduction system you select, and how your house is built."
There are zero energy losses with RadonSeal. In fact, if you already have a radon mitigation system, RadonSeal will reduce its energy losses by stopping the suction of treated air through the slab into the radon fan.
EPA: "Radon reduction systems need occasional maintenance. Warning device should be checked on a regular basis to make sure the system is working correctly. Fans may need to be repaired or replaced (manufacturer warranties usually do to exceed three years). Replacing a fan will cost around $250. Testing radon level at least every two years will confirm that the fan is still performing well. The filters in an Heat Recovery Ventilation system require periodic cleaning and should be changed twice a year, and the ventilator should be checked annually by a professional to make sure the air flow remains properly balanced."
RadonSeal has zero maintenance costs. Re-application is not needed. The seal is permanent.
Radon mitigation fans draw not just soil gas from the ground but also indoor air from the house through cracks and pores in concrete. This may cause back drafting and spillage of combustion gases from the furnace, water heater, or fireplace in modern, tight houses. Installing a CO alarm is a good idea. Lung cancer may kill someone in 20 years, but carbon monoxide can kill them in 20 minutes!
The risk of back drafting increases when house air tightness increases and atmospherically vented appliance are present. Houses are already depressurized due to combustion appliances, exhaust fans like in the bathroom and kitchen (may exhaust 750 cfm), clothes dryers, range hoods, natural "stack effect," etc. The radon mitigation fan flow of say 100 cfm is comparable to a clothes dryer. In a leaky house, this may reduce air pressure by only 1 Pa but in a tight house, it may produce depressurization of 5–10 Pa which will reverse chimney flows. If the house is already depressurized at say 4 Pa, adding the radon mitigation system may take it over the limit of 5 Pa.
Building codes recommend that each appliance should provide its own make-up air. However, they rely on passive openings but dependent on wind direction, they may actually draw more air from the house. Spillage resistant appliances (e.g. direct vent gas appliances) are a much more reliable solution.
EPA: "When radon is vented from the radon mitigation system it tends to sink and there is a danger of radon re-entering the building through doors and windows due to the vacuum ("stack") effect. To prevent re-entrainment of radon, the point of discharge from vents of fan-powered soil suction and block wall suction systems must meet all of the following requirements: (1) be above the eave of the roof, (2) be ten feet or more above ground level, (3) be ten feet or more from any window, door, or other opening, and (4) be ten feet or more from any opening into an adjacent building. The exhaust point should be positioned above the highest eave of the building and as close to the roof ridge line as possible."
RadonSeal avoids the dangers of radon re-entrainment by leaving the gas where it belongs - in the ground. It does not create an invisible cloud of radioactive gas which, being 8 times heavier than air, tends to settle and deposit radioactive particles in the immediate surroundings.
(Source: "The Consumer's Guide to Radon Reduction" by EPA)
Covering exposed earth in basement reduces ingress of radon, as does sealing cracks and openings in ground level walls and floors.
Drain tiles can be placed surrounding the foundation and vented away from the house (the drain-tile suction method). This method is designed to pull radon from the soil surrounding the house and vent it away from the house.
Sub-slab suction is more difficult to accomplish, as it involves placing pipes under the house (laterally through side walls or by drilling holes in the concrete slab). A fan is used to vent these pipes away from the house.
Concrete block walls can be vented by sucking air from the hollow spaces in the wall and venting it away from the house to prevent radon from re-entering.
Lastly, there are methods for decreasing negative pressures within the house by bringing air into the house in proportion to losses from chimneys, dryers, etc., or by positive pressure including basement pressurization by blowing air from upper floors into the sealed basement.
There is a common belief that radon should be reduced by venting the basement. But depending on the house construction and tightness, it may actually increase the inflow of radon from the ground. The high energy losses in heated or air-conditioned air make this method impractical.
Some people believe that paints and surface sealers, particularly epoxy or rubber-based, stop radon. However, a layer of paint or even a polyethylene sheet has no chance of stopping radon atoms. Moreover, alkalis carried by moisture from inside the concrete attack the paint and cause its cracking and eventual peeling. EPA has tested all possible paints and surface sealers but concluded that they are not effective.
Sheetrock, wallpaper, plaster, or even polyethylene sheets do not stop radon. Covering floors with carpeting or linoleum does not work either. Remember that even several inches of concrete cannot stop radon.
Some builders believe that the plastic vapor barrier under the slab will stop radon. Although it is a part of the "radon resistant" construction, it merely reduces the flow of soil gas. But it cannot stop the diffusion of radon and its accumulation underneath the floor. That's why EPA properly calls it the "soil gas retardant" membrane.