The following case study was undertaken by Klas Haglid in his 7,000-plus-sq.ft. New Jersey home to determine how much of a risk radon levels play in his family’s life. He wanted to see how far he could lower the levels and therefore cut the risk of radon-induced lung cancer proportionately.

Background: To ensure proper radon control, you need continual monitoring and a proper mitigation strategy. If you think the decent radon levels next door are good enough for you, think again. Your neighbor’s numbers have little to do with the levels in your home, so you can’t use generally low levels in your area to claim you are safe. In addition to the amount of radon present in the soil surrounding your home, your radon levels can fluctuate wildly depending on the air-pressure differentials (APDs) of the moment. You say a professional ran a test when you bought your home and the radon level met code? A one-shot radon test performed for your home inspection will merely provide a snapshot of a day in the life of your home’s radon levels. More importantly, if the results show 4.0 pCi/L (the take-action level per the EPA) or less, you’re still prone to health risks. ADP’s, and consequently radon levels, are affected by everything from heating, use of appliances that exhaust air, seasons, severe storms and winds, and barometric pressure. This is because an excess of negative air pressure causes a vacuum effect which sucks up more radon from the ground and into the structure. Positive air pressure helps radon to leave. While eradicating radon completely isn’t feasible, you want to take those levels as low as they can go.

There are many strategies for encouraging the balanced air pressure that will mitigate radon and they depend on your home’s foundation and design. Some options are sub-slab suction, perforated pipes, drain tiles, sump-hole suction, sealing, and mechanical ventilation such as fans, heat exchangers and energy recovery ventilators (ERVs). Our study uses the positive pressurizing of fresh air via an ERV.


  • 7,452-sqft home with 5 bedrooms and 4 bathrooms
  • Airthings Home 223 Radon Detector (under $200) to take readings on each floor.
  • One BPE-XE-MIR-200 energy recovery ventilator (ERV) running at 110 cfm 24 hours a day, 7 days a week working with two 19-watts fans. Spec-wise, we are talking about a ventilation system that can take outdoor air and, via the use of a very long direct counter-flow heat exchanger, pre-treat the outdoor air from -10 F to 105 F–whatever the season–to a range of 60 F to 75 F with just the air mass you are exhausting.


I turned off the BPE-XE-MIR-200 to get a bare-bones reading of the radon in my home with the radon detector. While the basement reading was not through the roof, it did sit at 4.0, the level at which the EPA recommends acting to lower radon levels. However, there is still the risk of lung cancer at 4.0 pCi/L for 7 out of 1,000 non-smokers and 62 out of 1,000 smokers. For me, and I would think for most people, this risk is unacceptable.

After turning the ERV unit back on, I used the Electronic Radon Monitor again. Results were impressive: The first-floor reading was 1.62 pCi/L, which is well below the 4.0 pCi/L action level. The basement reading was higher at 2.08 pCi/L. However, this is still lower than the World Health Organization’s action level of 2.7 pCi/L.


The second-floor bedroom areas had a radon reading of 0.75 pCi/L for the 1st day monitoring period.  This is closer to outdoor air radon levels (0.02 to 0.75 pCi/L)and very encouraging. Reading accuracy over the course of a day is less than 20%, and over a week the accuracy increases to 10%.


Bear in mind that, while radon levels were pretty much halved throughout my home, the danger has not been completely eradicated. Basement levels of 2.08 pCi/L can still deliver a 4 in 1,000 chance of ‘The Big C’ to non-smokers and a 32 in 1,000 chance to smokers. That might not sound like such terrible odds-unless you are suddenly one of the victims.


Now, those risks can be cut by half or more again by simply using a more powerful unit. I will install an ERV in the 400-cfm range relatively soon even though ASHRAE Standard 62.2-2013 recommends a ventilation rate of 127 cfm for a home this size.

Recently, I went on vacation for one week. I shut the ERV fans off again, curious about the radon levels I would find returning home. While not pleased to discover they had risen to 3.1pCi/L, I was again impressed by the results. You can bet I turned that ERV right back on, pronto.


Added Benefits:

When you can install a $1,200 ERV that uses less energy than a 40-watt light bulb, there are benefits beyond the positive pressurization that lowers radon to outdoor levels. The ERV will also provide superior indoor air quality (IAQ) in very cold or very hot weather in an energy-efficient manner.  It should also be noted that CO2 levels throughout the home are very low, currently at less than 500 ppm or close to fresh outdoor air. See photo below.


And while providing that fresh air, my home’s 200-cfm ERV is running at well over 80% thermal efficiency, so the cost for the fresh air is very little or less than just having a drafty house or allowing warm air to simply drift up the bathroom exhausts!



  • Positive pressurization utilizing an ERV is a realistic solution for home radon levels higher than naturally lower outdoor levels. While there are other solutions, such as installing a dedicated outdoor air HVAC system that would cost tens of thousands of dollars-or moving–ventilation via an ERV can be set up in a couple of hours on a Saturday with reasonable do-it-yourself skills.
  • You need to monitor radon on an ongoing basis and address elevated radon levels.
  • The radon detector purchased through Amazon (for less than $200) showed up the same day! Although it is true that you need to have a certified radon technician on the scene for real estate transactions, it is worth it to monitor radon on an ongoing basis.
  • The highest radon reading was in the basement, but it was still half the action level with the use of an ERV, which pulled 121 cfm out of the basement and introducing over 146 cfm on the first floor.  In addition to pulling the stale radon-infiltrated air out of the basement, positive pressurizing the first floor gave excellent CO2 and VOC air quality.
  • The second-floor bedroom areas had a radon reading of 0.75 pCi/L for the 1st day monitoring period.  This is closer to outdoor air radon levels and was achieved with the ventilation rates from ASHRAE std 62.2-2013.
  • The current action level of 4 pCi/L leaves an average of 7 people out of 1000 with lung cancer that leads to death.  The goal should be to greatly reduce indoor radon levels as close as possible to outdoor levels or a reading below 1 pCi/L.  In extra-challenging locations, sub-slab ventilation should be used along with the ERV to achieve a lower radon level.
  • Radon is a colorless, odorless radioactive gas that kills over 21,000 people a year in the United States, which can be effectively remediated through under the floor and whole house ventilation.

We are looking for feedback on your experiences with radon issues! Please drop us an email at, tweet, visit our Facebook or LinkedIn page and answer the following: Were you fully aware of the dangers of radon before reading this article? Do you know your radon level numbers? If so, what are they and do you feel you need to do something about them? Have you done something about them? What?

We hope this series will be food for thought in bringing more attention to the very real and unnecessary deaths caused by indoor radon exposure. The fact is, if you live above the Mason-Dixon line, you have a radon issue. Good ventilation practices are one way of taking control of home radon levels.