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Q&A Spotlight

Radon Mitigation in a Leaky House

A reader weighs the pros and cons of various ventilation options as a way of lowering the health risks from radon

Nineteenth century charm and 21st century air quality problems. The log house, built in the 1830s and sided with more conventional materials, has several crawlspace and basement areas beneath it. Ridding the house of radon has been a challenge.
Image Credit: Images #1 and #2: Andrew S

Radon mitigation in new construction is now routine when testing finds that concentrations of this odorless, cancer-causing gas exceed government-recommended levels. Writing from southeastern Wisconsin, Andrew S. has a slightly different problem: How to control radon levels when you live in a leaky log home built in the 19th century.

“Our radon issue is being worked on via traditional methods with mixed success,” he writes in a Q&A post at GreenBuildingAdvisor. “The radon issue improves dramatically when windows are open — I assume this is dilution and perhaps also pressure equalization?”

That may be fine in warmer weather, but leaving windows open during the winter in Climate Zone 6 to keep the concentration of radon under control doesn’t seem like much of a solution.

Andrew wonders whether other forms of ventilation might help. He weighs two possible options:

  • Positive-pressure ventilation, possibly by means of a dehumidifier that draws outside air into the house. “Might the positive pressure help reduce radon soil draw and simultaneously dilute the radon issue?” he asks.
  • An energy-recovery ventilator. “Does a balanced system ever make sense in a leaky home?” Andrew wonders. “The house also has some negative pressure devices (bath fans, boiler, wood stove insert). The goal here might be simply to dilute bad air whereas a positive pressure system may dilute but also prevent tendency to draw bad air in.”

Andrew knew about the radon problem when he bought the house, but he was assured by a well-recommended radon specialist in the area that controlling it would not be a problem. When the sale went through, that expert came to look at the house — and never came back. Other contractors have looked but never followed through with a plan. Although Andrew has found a contractor who’s willing to work on the…

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  1. agazdik | | #1

    Our problem is Radon in winter caused by the stack effect. We have a 1950s ranch in Pittsburgh. The basement level is above grade at the back of the house as we sit on a sloping lot. The home has a conventional radon system with functioning fan. When we purchased the home 7 years ago it passed the Radon test in September . However, last winter I installed an Airthings Monitor and discover the levels get as high as 23 in winter but are less than 1 all summer. We use the basement as an office, artist studio and workout area. These are the actions that I am considering;
    1. Install a HRV system to dilute the Radon & reduce pressure differential between floors.
    2. Sealing the attic
    3. Might add a sealed basement door to reduce airflow. Seems like this should help, but, I am not sure.
    Question should the HRV have its intake and discharge directed only to the basement or should it be tied into the home ducts? Please let me know your thoughts? Thanks, Art

  2. charlie_sullivan | | #2

    It might be partly your heating system creating low pressure in the basement and driving leakage. What kind of heating system? Getting the ducts (?) tested for leakage and sealed might help.

    If it's stack effect, sealing the attic leaks should help reduce suction on the basement and reduce radon levels. A sealed basement door might help a little but not much because there are lots of other ways air flows between floors. It might be that your mitigation system is underpowered and needs a boost in the winter, or it might be that there are foundation cracks or penetrations that are part of the problem. My foundation had a 1x1 chunk of wood penetrating the foundation at each corner--some oddity of how they did the form work in 1970--that rotted out leaving a 1" square hole there.

  3. agazdik | | #3

    Charlie: We have a forced air system. We have a quote from a contractor to Aeroseal the supply and return ducts and to seal the attic. Maybe that should be our first project.

    By the way there is no need to operate the Radon fan in the warm weather months since the levels drop naturally due the reversal of the stack effect in summer. Thanks, Art

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