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.