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, Jan, 20, 2015 @ 10:01 AM


 radon testing

January is RADON ACTION MONTH in the United States.  With the holiday season behind us, we're staring winter square in the face. It's a good time to think about testing your home for radon.  Even if you have a radon in air mitigation system, the EPA recommends follow up testing every two years.  There is no "safe" level of radon.  In fact, there's an associated risk of lung cancer with exposure to any level of radon.  The EPA's 4.0 pCi/l Action Level is a level at which to take "ACTION" to reduce radon concentrations and reduce exposure risk...it IS NOT a "safe level"!

describe the image

 Radon in air concentrations fluctuate in direct correlation with weather conditions.  Winter time is "worst case" scenario for radon testing due in large part to the "stack effect". 


stack effect RADON ACTION MONTH gives us an opportunity to think about radon exposure and the threat it presents to our families and loved ones...at a time of year when we are most likely to be exposed to the highest radon concentrations for the longest periods of time.  If the home has a private water well as its' water source...the water should also be tested for radon in water concentrations.

Many home owners have the misconception that one radon test below 4.0 pCi/l indicates a  "radon free" home.  This flawed thinking translates into countless cases of unintended exposure to elevated radon concentrations by unsuspecting home owners and their families.  Many of these victims of circumstance can trace their unrealized exposure dilemma back to the purchase of their home. " But when we bought the home - there was no radon" is a phrase that is all too commonly recited by disenchanted homeowners selling their home and having to mitigate elevated radon levels before they can close the sales transaction.

The largest percentage of homes mitigated for radon are a result of the home inspection process during a real estate transaction.  Paradoxically, the largest number of unsuspecting homeowners being exposed to elevated radon levels on a yearly basis are a result of the home sale / inspection process. Here's why...

 Home inspections are an integral component of the real estate transaction process. Radon testing (or a real estate radon screening measurement) is part of this process.  When a "for sale" home tests high for radon... most often it is mitigated before title is transfered.  When considering that the real estate market - in general - realizes maximum sales volume in spring and summer, many of these home inspections yield "low" or "lower" radon screening results simply because of the time of year the home is being tested (inspected - sold). 

Unfortunately, most homeowners never bother to follow up with a cold weather radon test. This oftentimes results in homeowners being exposed to elevated radon concentrations (albeit for a portion of the year) for as long as they own their home, because they have been lulled into a false sense of security by the one low result they got at the time of the original inspection / test.  

radon testing devices

Radon is a class 1 carcinogen...it is the number one source of lung cancer in non - smokers, is naturally occuring, is on the periodic table of elements, is found everywhere to some degree, is colorless, odorless, and tasteless, is easy to test for, is fixable...and most importantly - IS REAL!  It's RADON ACTION MONTH...  TAKE ACTION! - test your home today! 



certified radon mitigator and testor

Topics: radon, radon mitigation system, radon testing, radon in air concentrations, real estate screening measurements, radon action month


Posted by Matthew Bednarz on Wed, Sep, 05, 2012 @ 14:09 PM

radon mitigation systems

Active Soil Depressurization (ASD) is the most common radon mitigation system or technique utilized to mitigate elevated airborne radon concentrations. The installation process involves installing PVC pipe through the slab of the structure, and routing the pipe up to the roofline of the structure.  An in-line fan is connected to the pipe.  This in-line fan creates a suction or negative pressure on the sub slab fill thereby intercepting radon and soil gas before it has a chance to permeate up through the slab.  The radon and soil gas is vented safely outdoors, above roof line.      


ASD system routes

ASD is the most commonly employed radon mitigation technique because of cost, effectiveness, and relative unobtrusiveness.  The most common way to install an ASD system is the exterior route option.  This involves the fan being positioned on the exterior with the vent routed to the roofline up the exterior of the building.  This routing is most common mainly because a larger percentage of radon mitigation work is paid for by the seller of a property during a real estate transaction.  very often, an ASD system can be positioned on a portion of the structure that is considered utilitarian.  However; this isn't always the case. 


Exterior route ASD system resized 600 

Since an ASD system becomes a permanent fixture in a home; some consideration should be given to potential route options that might exist for the ASD installation.  An interior or garage route are oftentimes available, but overlooked due to increased install expense.  On average; a garage or interior route option adds about 20% overall expense to the install.  Not significant when considering an average ASD install expense of $1,200 and the fact this is a permanent fixture in a home or building.

If you're purchasing a home that needs a system; get involved in the decision process!  The seller's responsibility is to get the radon levels down - not necessarily to give you the prettiest install possible.  If you're having a system installed for the benefit of your own family, consider future resale value.  Radon fans are made to be mounted externally; but if it can be shielded from sun & ice - why not?  

This is the very reason why we visit the jobsite to quote on ASD installs.  Nuances such as; view from the road, window locations, roof pitch, electrical availability, access in basement, and a multitude of other factors simply cannot be determined by a phone conversation.  Old tag lines such as; "we've done plenty of work in your neighborhood" or "area" simply don't hold water. 

Sometimes there's no choice but to route the system externally.  We can do everything we can to minimize aesthetic impact.  Remember that there are oftentimes alternative route options or locations. In most cases - it is well worth exploring these alternatives for your radon mitigation system installation. 

exterior route ASD system

 certified radon mitigator


Topics: airborne radon concentrations, radon, radon mitigation system, active soil depressurization, ASD, radon fan

Indoor Airborne Radon Concentrations

Posted by Matthew Bednarz on Tue, Jun, 26, 2012 @ 11:06 AM


Airborne Radon Mitigation

Climatic conditions have a great affect on indoor airborne radon concentrations.  Radon entry into a home via the soil is predicated on pressure differentials that exist - or that are developed - between the interior & exterior of the home.  Low barometric pressure (the kind of atmospheric pressure that typically accompanies adverse weather) will allow for greater influx of soil gas - hence, radon...into the structure.

A rainstorm will not only include this drop in atmospheric pressure, but will oftentimes include winds that increase pressure differentials within a building. Saturated soil that prohibits the natural flow of soil gas from emanating through the lawn surrounding the house to redirecting flow into the basement is another contributing factor to spikes in indoor airborne radon concentrations.

If rainfall is substantial enough, a troublesome remnant will be saturated soil under the basement slab.  since a typical Active Soil Depressurization (ASD) system relies on creating suction / air movement below a basement slab to mitigate radon; damp or wet sub slab material will impede the radon mitigation system's ability to create a successful sub slab pressure field.  This may be a temporary occurrence or it may be a permanent change due to geologic shifts, changes in landscape, etc.

If a radon mitigation system seems to periodically get louder - or a "swishing sound" can be heard emanating from the pipe; this may be indicative of saturated soil conditions under the slab.  Homeowners should beware that during these conditions; reduction capabilities of the mitigation system are likely diminished.  If this scenario becomes commonplace; the homeowner should strongly consider installing a sump pump and possibly some draintile to help lower the water table under the slab.  This may even become necessary in basements where there is no previous sign of water infiltration.  Water is problematic for ASD systems and can impact indoor airborne radon concentrations.

NEHA Certified Radon Mitigator

Topics: airborne radon concentrations, pressure differentials, radon, radon mitigation system, active soil depressurization, ASD, mitigate