CT Basement Systems Radon Blog by Matthew A. Bednarz V.P.

News for Homebuyers Regarding Radon Resistant New Construction

Posted by Matthew Bednarz on Fri, Jun, 19, 2015 @ 16:06 PM


Home Buyers: Know What to Ask For

Basic Radon-Resistant New Construction Techniques for Your Home

Based on a rash of recent poorly engineered prefab radon system experiences, I felt it necessary to rehash an old post.  All of the techniques and materials described below are commonly used in home construction.  While the techniques may vary for different house foundations and building site requirements, the five basic features that should included in new construction to prevent radon from entering the home are:

cutaway of house with mitigation system
NOTE: If code allows; alternatives such as a soil gas collection mat can be a viable option.  
  1. Plastic Sheeting or Vapor Barrier / Retarder: Place heavy duty plastic sheeting (6 mil. polyethylene) or a vapor retarder on top of the gravel to prevent the soil gases from entering the house. The sheeting also keeps the concrete from clogging the gravel layer when the slab is poured.             

  2. A Vent Pipe: Run a 3-inch or 4-inch solid PVC pipe, vertically from the gravel layer (stubbed up when the slab is poured) through the house’s conditioned space and roof to safely vent radon and other soil gases outside above the house.  Whenever possible - 4" pipe is a better choice as it allows for up to double the volume of air to be removed out from under the slab as compared to 3".                                                        

  3. For very large footprints, multiple vertical stacks are recommended.  We did a project in a Greenwich estate that had 6 stacks. (Although serving a different purpose, this vent pipe is similar to the drain waste vent, DWV, installed by the plumber for the sanitary system.) This pipe should be labeled "Radon System."       

  4. Sealing and Caulking: Seal all openings, cracks, and crevices in the concrete foundation floor (including the slab perimeter; floor wall joint) and walls with polyurethane caulk to prevent radon and other soil gases from entering the home.                

  5. Junction Box:  An electrical outlet should be provided near the pipe location in the attic.  This is allows for easy fan connection in the event the system has to be activated to effectively reduce radon concentrations.

Some common mistakes made with radon resistant construction pipe installation are;
  • inaccessible attic locations (pipe located where no one can fit),
  • slab stubs located at opposite end of basement from ceiling stub (results in excessive pipe runs),  
  • multiple slab level layouts not being addressed.
Homes located in areas that have water wells should have a second or independent stack installed from the basement ceiling as close to the well tank as possible, to the attic floor.  In the event the water is found to have elevated radon levels, an aeration system will need to be installed.  This system requires a separate exhaust stack.


Topics: radon resistant construction, radon mitigation, radon in air, radon mitigation system, radon testing, radon in air concentrations, indoor radon in air levels, Radon Air, radon mitigation fan, radon concentrations

Radon Map of CT

Posted by Matthew Bednarz on Tue, Jul, 01, 2014 @ 13:07 PM

 Test for Radon

The Radon Map of CT only begins to tell the story of the prevalence of radon in the state of Connecticut.  CT Basement Systems Radon Inc. has been in the radon mitigation and radon testing business since since 1987.  Through the years, we have seen many homes test "high" for radon in zones or counties where the radon "potential" was thought to be lower.  Conversely, we have have tested many homes that resulted in radon levels below 4.0 pCi/l in areas designated as having a higher radon potential.

 CT Radon Map

radon masp legend

While the Radon Map of CT may be useful as an introductory tool for radon risk assessment, it should not be the only benchmark utilized in determining whether or not a home has a radon problem.  Radon is a very "site specific" danger.  We have seen streets in neighborhoods where 9 out of 10 homes have elevated indoor radon in air levels.  We have also seen neighborhoods where only one or two homes out of 20 have elevated airborne radon levels.  Much the same can be said for radon in water levels.  A neighborhood of homes with private water wells can have a wide range of waterborne radon levels even though the wells are within close proximity to one another.

Variation in airborne radon levels is not something limited to only larger tracts of real estate.  I have personally tested homes that have shown variations of up to 100 pCi/l from one end of the home to the other at the very same time of testing.  We attribute these variations to differences in soil composition that the home is built.  Radon (and radium) are part of the Uranium 238 decay chain.  It is possible to have a structure with a sufficient enough of a footprint, to cover a piece of real estate that has a significant variable in its' radium content; thereby resulting in appreciable differences in airborne radon concentrations. 

The topography of a given piece of land is not a good indicator of the "radon potential" for the structure to be built on it.  Ledge and rock are not reliable barometers for scoping out potential radon problem areas.  I have tested plenty of homes with exposed ledge outcroppings within the structure...and have had numerous test results yielding radon concentrations <4.0 pCi/l.  As a company, we mitigated a home in Glastonbury CT, with indoor airborne radon levels of 900 pCi/l...yet Glastonbury is located in a "low radon potential" area on the Radon Map of CT.  The only way to know is test your home!  Don't forget - if your home has a private water well...test the water for radon also!

 Contact us for Radon  Information

NEHA Certified Radon Tester 

Topics: radon, radon testing, indoor radon in air levels, airborne radon, radon concentrations