Image description


A local company with local employees keeping money local in Lawrence, KS.

Radon Mitigation and Building Science

A mitigation system stops radon from entering your home by extending a slight vacuum under the house to direct the gas towards the outside. Concentrations are typically reduced by 80-99% (or to less than 4 pCi/l).


Image description

Mitigation Process

Step 1:

Blower Door Test

Image description

The first stage of the process will be the performance of a blower door test to diagnose the building air pressure.  Your house will be depressurized using a large fan, and this will allow leaks to be detected and airflow into the house to be measured. This information is used to locate problem areas that pull radon into your home.  Most houses have some degree of what is called the chimney effect.  The chimney effect is the upward pull of air from the basement into the upper portions of the home. Temperature differences between the inside and the outside of the house, combined with openings (air bypasses) to the exterior of the house cause this effect.  One common opening can be where the flue chases (openings) for the combustion appliances exit through the house. Radon may be drawn upward into the home through these openings.  Detection of problem areas and potential air flow problems is essential for effective remediation. 

Step 2:

CAZ Test

Image description

A CAZ (Combustion Appliance Zone) test will be performed before and after the radon mitigation system is installed.  We want to ensure the health and safety of your home.   We do this by testing the carbon monoxide levels that are emitted from your furnace and hot water heater.  Installation of the radon fan depressurizes the area underneath the basement floor slab and sometimes unintentionally inside the basement.  As a standard part of the installation process, our company then retests your radon and carbon monxide levels to assure that the system is working properly.

Step 3:

Mitigation System


Image description
Image description
Image description
Image description

• A  3-4 inch diameter plastic pipe is installed, beginning in the soil beneath the slab, passing through the basement slab into and through the basement. The pipe must then extend upward to discharge the air above the roof eaves.

• After the pipe is installed and exits the house, a fan is mounted to the pipe to draw the radon gases out.  The energy cost to run the fan is dependent upon the size of the fan required, and can range from one 20 to one 160 watt light bulb. Since fans are usually difficult to hear, a pressure gauge is required to provide a visual check to verify the continuous operation of the fan. 


• Next any accessible openings and cracks in the walls and floor of the basement are detected using negative pressure and a smoke system, and then sealed.  Sealing large cracks in the basement slab prevents some radon from entering the living space, and is typically a component of the radon mitigation system.  However, regardless of meticulous sealing efforts, a substantial leakage can still exist undetectable to the eye in inaccessible areas. 


• One of the most important radon prevention measures is sealing the return air ducts to the heating system. Air ducts often have loose seams or large openings allowing air from the basement to be pulled into the ducts.  Leaky return ducts, in addition to pulling radon into the return air ducts, which in turn provide air to the supply ducts for the entire house, also can pull CO and flue gases into the house.  When we add to this a powerful radon fan that depressurizes the basement slab, the pull from both leaky ducts and radon fan combine in to create a situation ripe for back drafting of radon and flue gases into the house.  By sealing the ducts we decrease the amount of radon that needs to be mitigated and prevent flue gases from entering the returns.

• Finally, after sealing cracks in the slab and ducts, we again use the blower door to look for and diagnose any remaining leaks missed in the sealing process.  In addition the CAZ will be rechecked to assure that all systems are interfacing correctly. 

Photo by Mike Yoder, Lawrence Journal World