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


Posted by Matthew Bednarz on Tue, Jul, 08, 2014 @ 13:07 PM

 radon mitigation in CT

We oftentimes get calls about "radon fan noise".  These calls are most prevalent during winter cold snaps and after heavy rainfalls.  The short answer regarding the fan noise is; "There has been a change in resistance placed on the fan".  The more complete answer deserves a closer look at extenuating circumstances. 

To best illustrate the impact of cold and rain on radon fan noise, lets' first review the most common approach taken to mitigate airborne radon in air levels. Active Soil Depressurization (ASD) is a process that involves inserting a pipe through the slab of a structure, and routing to the roof line.  An in-line fan is connected to the pipe to draw the radon bearing soil gas out from under the slab, and exhaust it at the roof line of the structure.  This method effectively "intercepts" the radon before it ever has a chance to rise up through the slab, making it the most effective and efficient radon mitigation strategy.

ASD Route Options

Soil gas (of which - radon is a component), remains somewhere around 55 degrees throughout the year.  This results in a constant condensation factor within every radon in air mitigation system.  In fact; a properly installed ASD system has a constant pitch in the pipe back to the slab to allow for condensation to drain back under the slab. 

With sub - freezing outdoor temperatures enveloping the exhaust pipe and fan of an exteriorally routed ASD system, the moist air within the system condensates more readily and soon freezes.  The end result; a reduced inner diameter on the exhaust pipe, and ice formation within the fan.  These two conditions will most definitely cause a fan to become louder in operational noise.  There is no perfect solution to resolve this. Temporarily shutting down the system until it can thaw may be the best approach.

Exterior ASD system in winter

An elevated water table under a basement slab is another contributing factor to radon fan noise.  Saturated soil - or water - prevents air flow through sub slab soil.  The added resistance of air movement through the ASD system creates more radon fan noise.  This is usually the reason why some homes will notice a louder operational noise after periods of rain.  Fluctuating water tables resulting from rainy seasons will also impact radon fan noise.  Gurgling in the pipe, or a swishing sound in the fan are telltale signs of water impacting the ASD system.  Sometimes turning off the fan for a few minutes will resolve the problem.  For chronic sub slab water issues, a sump pump or water proofing system may be needed.

We offer a service whereby we inspect your ASD system to identify if any potential problems exist with the layout and performance of your ASD system...we may also be able to help reduce radon fan noise.

Contact us to schedule a review of your ASD system

neha certified radon mitigator



Topics: radon mitigation, indoor radon in air levels, active soil depressurization, airborne radon