Radon Mitigation

To reduce radon gas in a home or building is called “radon mitigation”, “radon abatement” or “radon reduction”. The method of reducing radon in a building may require a combination of several processes which work together as a system most often called a “radon mitigation system”. The terms “mitigation” and “remediation” are often used interchangeably along with “abatement” and “reduction.” When referring to radon gas the terms “radon removal” and “radon remediation” can be misleading since it is practically impossible to remove all radon from many homes and buildings.

Since there is no safe level of radon, the goal of radon mitigation is to lower the level of radon gas as much as practically possible. We guarantee that our systems will achieve an average radon level less than 4.0 pCi/L and most systems achieve levels less than 2.0 pCi/L (these are the two radon action levels set by the EPA). the World Health Organization is recommending that homeowners take action to remediate the radon level in their home if it exceeds 100 becquerels (Bq), which corresponds to 2.7 picocuries per liter (pCi/L). That’s lower than the 4.0 pCi/L current action level in this country as recommended by the U.S Environmental Protection Agency.

How to Reduce Radon: Radon Mitigation Basics

1. “Sub-slab Depressurization” The most common type of radon mitigation system.

Download (PDF, 63KB)

This picture shows the basic components of a typical radon mitigation system. Usually a hole is drilled through the basement floor where a small suction pit is formed; a radon fan pulls the radon gas from under the floor through a PVC vent pipe; the fan is usually mounted in an attic space or on the exterior of the structure (the picture shows both options); the radon gas is safely discharged through the vent pipe at least 10 feet above the ground, away from windows, in most cases the termination of the vent pipe is either through the roof or above the side of the roof. Source for picture:  EPA/625/R-93/011, Page 8, October 1993

How Radon Mitigation Works

Simply put radon gas follows the path of least resistance. Typically radon gas is sucked into a home by a small amount of negative pressure existing in most homes. Radon can pass right through solid concrete if no cracks are present. Negative pressure is usually greatest when homes are closed up and heating systems are running. A basic radon mitigation system pulls the radon gas from below the basement floor before it enters the home and vents it to the outside air. The suction below the floor from the radon fan is greater than the negative pressure inside the home.

The EPA recommends radon mitigation when the concentrated levels of radon gas accumulate in a home to high levels and become a health risk. The movement of radon gas from the soil below into the structure is greatly determined by the ventilation rate in the enclosure. Generally, the indoor radon concentrations increase as ventilation rates decrease, so a house may test OK for radon during the summer and test high in the winter.

In a well ventilated home or an old drafty house, the radon concentration tends to be very similar to the outdoor level and usually does not pose a problem. Unfortunately one of the drawbacks of a highly insulated, “air sealed”, energy efficient home is very little fresh air circulation. Tightly sealed, energy efficient homes can trap radon gas causing it to build up to undesirably  high levels.

Radon levels in indoor air can be lowered in a number of ways, from simple methods of sealing cracks in floors and walls to increasing the ventilation rate of the building. These simple techniques, alone, most often are not effective at lowering high levels of radon but can prove to be adequate if the radon level is slightly elevated. Remember that small radon molecules can travel through concrete once cracks are sealed.

Five principal ways of reducing the amount of radon:

1. Improve fresh air ventilation
2. Radon resistant construction and or a passive radon vent pipe tied into drain tile system for basements
3. Installing a radon fan with a sub-slab depressurization system
4. Sealing floors and walls
5. Installing a positive pressurization or positive fresh air supply ventilation system

Positive-pressure ventilation systems, blow fresh air into the house and in cold climates can be combined with a heat exchanger to recover energy in the process of exchanging air with the outside. These systems are being put into many new homes for improved indoor air quality, with the added benefit of reducing trapped radon. Exhausting basement or first floor air to the outside is not necessarily a viable solution as this can actually draw radon gas into a dwelling, making it worse. Homes built on a crawl spaces however can often lower radon be increasing fresh air ventilation to the crawl space and placing a vapor barrier or “radon barrier” (a sheet of plastic that covers the crawl space), that is sealed at seams and at the wall.

ASTM E-2121 is a standard for reducing radon in homes as far as practicable below 4 picocuries per liter (pCi/L) in indoor air. The EPA has also set 4.0 pCi/L as an action level, when the average radon is 4.o pCi/L and above, in the living area of the home, the EPA recommended to take action to lower it.

Note: the EPA also suggests you may want to consider radon mitigation if the average radon level is 2.0 or higher in some cases, (ie when occupants especially toddlers or children home all day, and or  playing on or near the floor). Radon is usually tested above the floor on a table or shelf, but the radon level at floor level can be double or more.