Avoiding Radon Problems in a Slow Market

Services for Real Estate Pros with The Home Inspector General

I have been retired for the Real Estate home inspection business since January 2007. After 20 years I decided to focus on consulting in the home performance and environmentally friendly construction fields. Even though a good part of my time is spent traveling and speaking about environmental construction and building performance issues I still receive my fair share of calls for home inspections.

I also receive a lot of calls from agents looking for advice on problems uncovered during recent home inspections that are potential "sales stoppers". Recently I have received a lot of calls concerning high radon levels. The EPA set a recommended abatement level of 4 pCi/liter of air. This number is arbitrary, initially they were pushing for 2 pCi/liters per liter of air so we should count our blessing at the higher level.

Radon is an odorless, colorless gas that is the breakdown of uranium found in the ground. Radon is not harmful in spite of the media hype. What is harmful are the daughters of radon, the decay products of radon that breakdown and release harmful alpha radiation capable of harming soft cell tissue (specifically the DNA chain).

Radon enters the home through structural cracks and joints in the foundation walls or slab, through blocks or rocks in the air that is drawn through the soil. The soil gases are drawn into the house because the house has a significant thermal updraft resulting from hot air rising in the house, exiting through the ceiling penetrations. Any air leaving the house has to be made up from areas below the leaks. So radon can actually be sucked into the house.

When a house sits vacant for a long period of time (and we see a lot of that in this market) the radon builds up. A house sitting empty with no human activity can develop radon levels several times its normal level. Add to that a long dry summer that causes the soil to dry out, creating cracks in the soil that allow radon gas to travel up and into the house easier and you have a recipe for a failed radon test.

If you have a house that has been sitting for a long period of time you should air the house out to ensure a fair and accurate radon test. Open all the windows, on all levels, for 8 or 10 hours. Then close the house for at least 24 hours prior to a scheduled inspection. This method is approved EPA protocol for post mitigation testing so don't feel like you are cheating the system.

If the radon numbers come back high, above 4, you can put in a system to reduce the potential for a problem. If the numbers are high but below 20 I would suggest that you escrow the funds to install a radon reduction system but retest the house for one year before doing so. An alpha track testing device can be installed in the home after the new owner takes possession. The house is not kept closed, rather it is lived in normally. After one year, the test cannister is sent to a lab where it is evaluated under an electron microscope. They technician counts the number of scratches n the exposed film in a given area of the test cannister and extrapolates the year average. If the average is below 4 the escrow is released to the seller. If the results are high the funds are used to abate the problem.

While this sounds like a pain in the process it really is a prudent way to solve this problem. The seller shouldn't be forced to put a system in based on test results that average two days (which only reflect the potential for a problem) when the goal is to abate annual rate problems. A buyer should not want a system installed just for the sake of having a system installed. Sub slab suction systems have an $90/year operating cost in energy use and deferred maintenance. They also suck conditioned air out of the house at an annual cost of $60/year or more.

If you handle the initial report results wisely you can not only save the deal but do the right thing for both the buyer and the seller.


The General

Comments (11)

Stephanie Edwards-Musa
thredUP.com - The Woodlands, TX
knitwit at thred UP

Hi Michael,  this is very good information.  I have always heard that radon is more of an issue in some parts of the country more than others.  Is there any truth to that?

Aug 24, 2007 11:02 AM
Michael Holcomb
The Home Inspector General - Grand Rapids, MI

Radon can be found almost anywhere. In fact, the average concentration of radon in the air is around 0.3 pCi/liter of air. Mountain states are prone to higher concentrations due to the amount of uranium in the ground. In the Grand Rapids area about 1 out of 7 homes have elevated radon. There are pockets where the problem may exceed 7 out of 10 homes. Periodic testing is recommended for every home. The most accurate tests are continuous radon monitors. Charcoal cannisters have a 68% accuracy rate with as many false positives as negatives.

The General

Aug 24, 2007 11:56 AM
Mary McGraw
GLREA - Rockford, MI
2015: Solar Energy Is Still A Simple Machine!

Mike - Good information. It is very interesting that we are seeing increased amounts. I am glad you have explained the reason why - homes sitting vacant. It makes me curious - my cabin is a "berm" home - the majority of the living area is basement level. It is closed up during the week and used on weekends but the lower level is never very opened to venting from the outside. It's cool so normally on the lower level just the entry door is opened.

It sounds like it could be a problem? The property is located north of Cadillac.


Aug 25, 2007 04:11 PM
Joan Mirantz
Homequest Real Estate - Concord, NH
Realtor, GRI, CBR, SRES - Concord New Hampshire
Welcome "General"...Mary just said you are a new member and a RESNET rater I'm just starting to get educated about Energy Star...and will probably pick your brain!
Aug 25, 2007 04:16 PM
Michael Holcomb
The Home Inspector General - Grand Rapids, MI


Berm houses are typically constructed in a manner that increases the potential for radon buildup. The more surface in contact with soil the greater the potential for radon buildup in an area with elevated radon levels. Dilution is the best option for reducing radon buildup in an existing building, especially one with a finished slab floor. First I would recommend that you use an inexpensive charcoal cannister to test the cottage. Four to seven day packets are available for free at The Alliance for Environmental Sustainability. Test the structure two different times (one should be in the winter months). If either test excess 4pCi/liter you should consider installing an ERV (energy recovery ventilator) to remove interior air and replacing it with fresh outdoor air (while saving the energy from the out-going air to heat the in-coming air). This would prevent the radon from building up. Or you could simply air the cottage out for an hour or two when you go on weekends. Set up a window fan to exhaust the cottage and open a window on the opposite end of the cottage to bring in fresh air.


The General

Aug 26, 2007 03:08 AM
Michael Holcomb
The Home Inspector General - Grand Rapids, MI


I have watched the real estate industry evolve over the past 20-years. During that time I have developed a variety of experiences that have transitioned my business from field work to seminars. I've enjoyed every step along the way.

During that time the home inspection industry has also evolved. Not all evolution is good as you probably know. I've conducted over 16,000 home inspections during my career. My extensive experience involved (at one time or another) certifications/expertise in the following areas:

  • Radon Testing
  • Lead-based paint inspections
  • Lead-based risk assessments
  • Mold
  • Indoor Air Quality
  • Energy Efficiency (Energy Star, RESNET, tax credits)
  • Green Building (Michigan, Ohio, Illinois, Wisconsin, Minnesota, Tokyo)
  • USGBC (LEED for Homes, LEED-NC, LEED-CI commissioning, LEED for Homes Faculty and Provider)
  • Green Communities (Enterprise Foundation Affordable Housing Program)
  • Infrared Analysis
  • Structural failure analysis
  • Forensic Building Performance Analysis
  • HVAC System Sizing/Design
  • Healthy House Audits

Sometimes I will have an answer that might be of value to your questions. Other times I will have a resource that I can refer you to, to get the answer you need. In I either case I invite you to pick away until there is nothing left.


The General

Aug 26, 2007 03:20 AM
Joan Mirantz
Homequest Real Estate - Concord, NH
Realtor, GRI, CBR, SRES - Concord New Hampshire
Michael (LOL)...I like you!!! We are going to have a GREAT relationship!
Aug 26, 2007 04:30 AM
Jeff Miner - Radon At Tahoe

Hi Michael,

I agree with your hold back instruction comments for the radon test during a real estate transaction.  Not many real estate agents seem to be aware of it.    I have a radon web site and a page dedicated to educating real estate professionals on how to deal with radon (this side of panic).  I have linked to your comments.

Jeff Miner
Radon At Tahoe

Apr 01, 2008 10:25 AM
Janet E. Campbell
Second Mile Radon Testing - Houlton, ME

   So the point of airing out a vacant house is to make the radon test " fair and accurate"? What's wrong with saving yourself some work and just having the test done in an unaired vavant house? Ideally, a radon test should provide the buyer with the home's hightest radon potential. A closed, vacant house represents this potential. While this airing out,followed by 24 hours closed house conditions, may be not be "cheating", according to the letter of the law, it is, in my opinion, unethical. If you were the buyer, how would you feel about this so-called "fair and accurate" airing out practice? Is the point of airing out a vacant house actually to make the house look good while disregarding the health of the future occupants?  It is true that more of the harmful alpha radiation comes from the radon decay products than from radon, but where do you think the radon decay products come from!? And it's a "blessing" that the action level is 4pCi/L rather than 2pCi/L!?

Jul 16, 2010 02:46 PM
Bruce Breedlove
Avalon Inspection Services - Colorado Springs, CO

[quote]If you have a house that has been sitting for a long period of time you should air the house out to ensure a fair and accurate radon test. Open all the windows, on all levels, for 8 or 10 hours. Then close the house for at least 24 hours prior to a scheduled inspection. This method is approved EPA protocol for post mitigation testing so don't feel like you are cheating the system.[/quote]

Wow! I have to agree with Janet on this one. What is the ultimate purpose of a radon test? Is it to provide a measure of the health risk from radon the future occupants will be exposed to? Or is it to help facilitate a transaction so the agents can get their commission checks?

Radon is a radioactive gas with a half-life of about 3 1/2 days. (Slightly longer but 3 1/2 days makes the math work easier.) Radon does not continue building up higher and higher in a vacant house because radon eventually decays away. A house that has been sitting vacant for 6 months (or some other long period) should not be expected to have a higher concentration of radon than if the house was "aired out" and then closed up for a day or two. Studies have shown that radon levels reach an "equilibrium level" after about 12 hours.

Suppose a house is closed up and left vacan for several months.  Beginning on Day 1 radon enters the house and is not diliuted by outside air. That is exactly what we want when we conduct a radon test so we can measure the potential for radon. (That is what the EPA protocols stipulate.) So a certain "amount" of radon entered the house on Day 1. And a similar amount of radon entered the house on Day 2 and Day 3 and Day 4 and every other day (fluctuating naturally with weather conditions and other factors).

Will the radon concentration in the house be 7 times higher after Day 7 than it was after Day 1? No. 75% of the radon that came into the house on Day 1 will have decayed away. Half of the radon present will have decayed away after 3 1/2 days and half of the remaining half will have decayed away after another 3 1/2 days. Similarly, the radon that entered the house on subsequent days will have decayed away at the same rate. After a while (generally 12 to 24 hours) the radon concentration will level off at the equilibrium level where the new radon entering the house equals the radon that is decaying away.

So it is impossible for radon to build up to higher and higher concentrations in a vacant house. Think of it like a bucket under a dripping faucet. Over time the dripping water can fill the bucket but if some of the water evaporated away at the same rate as it entered the bucket (somewhat like radon decaying away at a known rate) you would have a bucket with a water level that remained fairly constant.

Sep 09, 2010 12:03 PM
Janet E. Campbell
Second Mile Radon Testing - Houlton, ME

Thank you Thank you, Bruce! I had some concerns that what I had written here would get me  ... voted off the island. ...  And ... Hallelujah! ... you explained it much better than I could have done. There is a lot of misunderstanding concerning radon. I hope that  people here will gain a better understanding from what you've written.

Sep 15, 2010 01:44 PM