If your home has been tested and found to have a radon concentration higher than the EPA recommends (4 pCi/L), some of the methods below may reduce the radon concentration in your home.  Sub-slab depressurization will be the most effective. 

• Improving house ventilation
• Increasing air pressure within the house
• Sealing the entry points for the radon gas
• Sub-slab depressurization

Improving house ventilation:  This may be done with exhaust ventilation or air exchange ventilation systems.  In exhaust ventilation one or more exterior ducted fans (bath, kitchen, or whole house fans) are turned on creating a negative pressure within the house.   Without opening windows, air would come in due to negative pressure through all of the tiny spaces (around windows, doors, etc.) anywhere in the house.  This negative pressure would also increase the amount of radon coming in through the basement from porous block walls, cracks, sump openings in the slab, etc.  If windows are opened in the basement  and on other floors, fresh air coming in will reduce the radon concentration, especially if venting occurs through a bath fan in the basement.  This works well with an open stairway to the basement if additional windows or a door is opened upstairs.  More fresh air will be brought down to the basement.  Air exchange ventilation systems vent air in and out at the same time, maintaining the air pressure in the house.  In cold climates air exchangers should incorporate a heat recovery system.  Heating and cooling costs will be increased using these systems in cold and hot climates respectively.

Increasing air pressure within the house:  Active ventilation systems work by pressurizing the building.  A fan is used to force outside air into the building.  This works best if it can be done in the basement and the basement is tight.  (An open stairway leading to the upstairs would not make the basement tight).  The increase in air pressure forces air out of the building through spaces around windows and doors, bath and kitchen fan openings, chimneys, whole house exhaust fans, etc.  These systems are relatively simple and inexpensive to install.  In cold and hot climates heating and cooling costs would rise respectively.  If vapor barriers are not present, moisture problems may result in frost in the attic and exterior walls.  This could promote decay due to the growth of molds or other plant-like organisms.  In the winter in cold climates, the cold air brought in will usually contain less moisture then the air in your house.  This could possibly even decrease the moisture in your house.  However, it will increase the heating costs.   Keeping a positive air pressure in the house will lower the amount of radon getting in.  The amount of pressure maintained will depend on how well your house is built and repairs maintained.   

Sealing the entry points:  Sealing all around the foundation and floor and caulking large cracks and openings can help to reduce radon entry.  All cracks in the floor should be sealed. Radon can enter through very small cracks and openings that are too small to find and seal.  As the building settles, new cracks may form.  Any opening (excluding well maintained floor drains) through the slab should be sealed including sump pump holes which may need to be fitted with a sealed ducted cover.   If a cement block wall was used, the top level of the block between the block and the sill also should be sealed.  There is a product that can be painted on the walls and floors that is reported to seal radon out.

Some houses including trailer houses may have crawl spaces beneath them.  Sealing and/or venting the crawl space will aid in decreasing the radon concentration entering the home.  The ground should be covered with a polyethylene plastic.  All entry points into the home from the ground should be sealed between the plastic and those points.  The plastic should be sealed to the wall of the foundation.  Venting these crawl spaces well may decrease the concentration of radon in the space.  It will also aid in preventing the growth of molds and mildews beneath the building.  In that case sealing the bottom of the house with polyethylene plastic and all points entering the house may work as well or better then trying to seal the ground.  

Sub slab Depressurization:  The best way to reduce  radon is through sub-slab depressurization. Generally a hole is drilled through the basement floor (the "slab"), some of the soil (approximately a five gallon pail full) is dug out to create a hole, and a piece of plastic pipe is inserted into the hole. Now, there are three options.  (1) The pipe is run out through the basement wall and an inline fan is attached to it.  The pipe continues up the outside wall through the eave of the house and is vented into the open air above the roof.  (2) Instead of putting the pipe on the outside wall, it may go from the basement,  through the ceiling, into a closet, and into the attic.  A fan may then be attached to it before it is vented out through the roof.  (3) The pipe may also be built into one of the walls and continue into the attic where a radon fan is attached before it is vented through the roof.  The purpose of all radon fans is to create an area of low pressure in the small hole under the slab.  This pulls any gas including radon to that low pressure area.  The gas will be expelled into the atmosphere rather than then being pulled into the house.  (Without this, reducing the pressure inside the house would pull the gases (radon) from the soil into the house.)    If you decide to tackle the problem yourself and are looking for Do-it-Yourself radon mitigation help you may want to call your State Health Department or State EPA.  Below and to the left is an image from the EPA showing how the above mitigation may look. If you intend to hire a contractor the cost will likely run from $800 to $2600, depending on the size of the building and what has to be done.  You may want to look at the US EPA site or the State Health Department for a list of 'state radon contacts.'  They may be able to give you a list of qualified "radon mitigation contractors." Most United States Environmental Protection Agency (EPA) lifetime safety standards for carcinogens are established based on a 1 in 100,000 risk of death. Most scientists agree that the risk of death for radon at 4 pCi/l is approximately 1 in 100. At the 4 pCi/l EPA action guideline level radon carries approximately 1000 times the risk of death as any other EPA carcinogen.  (Source of the house image above- EPA Publication "Radon - A Physician's Guide:  The Health Threat With A Simple Solution")  Back 

What a home buyer should know?  All home buyers have the right and responsibility to examine their newly acquired home with a qualified home inspector. It may be done before signing a contract or after signing the contract as long as it is stated in the contract that the sale of the home depends on the inspection. (US. Department of Housing and Urban Development) Minnesota Department of Health recommends that all new homes in Minnesota be built to include radon-resistant construction features that minimize radon entry into the home and make future radon problems easier to fix should they occur.   Back to Radon Info Page or Back to FAQ'S