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Radon in a mixed-use multifamily high rise

User avatar
Danny Kelly | Posted in General Questions on

I have a client that is trying to sell a condo and the home inspection revealed an elevated radon level. The lender is requiring the radon to be remediated. Simple fix on a single family home on a crawl. I was thinking an ERV may do the trick. Any ideas, anyone heard of similar issues in multifamily construction?

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Replies

  1. Riversong | | #1

    I've never heard of dilution as a solution to radon pollution. It always requires source removal by negative pressure at the ground or below the slab. In high-radon areas, a passive stack on a sub-slab or crawl-space perimeter pipe brought the indoor radon down below the 4 pCi/L threshold in 95% of the cases.

    In multi-storey buildings, the higher interior stack effect will create a stronger suction at the foundation and it becomes even more important to mitigate at the footprint.

    I suspect that indoor air exchange (there isn't any in this unit?) would have to be excessive to control radon, and would come with a high energy cost.

  2. User avatar
    Danny Kelly | | #2

    Thanks robert - had a feeling the simple solution may not work. I am surprised that this was not taken into consideration during the design phase on a project of this scale. A lot of local theories say it could be the concrete in the building which is why I thought a single unit solution may be possible. Sounds like this could turn out to be a major fix.

    Not sure if there is existing fresh air exchange is there or not - building was constructed about ten years ago

  3. User avatar GBA Editor
    Martin Holladay | | #3

    Danny,
    In a single-family residence, Peter Yost successfully used a dilution strategy to lower indoor radon levels. Although this approach isn't as good as sub-slab depressurization, it's worth considering. Read more here:
    https://www.greenbuildingadvisor.com/homes/deep-energy-makeover-one-step-time

  4. User avatar
    Danny Kelly | | #4

    Thanks Martin. Interesting that the radon level remained the same in the crawl but went down in the house. I guess the dilution did not do much good in the crawl but the fact that there was a negative pressure in the crawl from the exhaust fan prevented the crawl air (and radon) from entering the home. After reading this - do not think my ERV idea will work unless it is on a very high CFM and then like robert said, will be wasting a lot of energy. Back to the drawing board - Thanks.

  5. Tony Kiburis, NH Radon Mitigator | | #5

    HRV's or ERV's will work as a radon solution for low levels of radon (say up to 7-8 pCi/L) only. Higher levels of radon require too much air exchange to dilute the radon to levels below the EPA Action Level of 4.0 pCi/L. The higher the air exchange level the higher the heating or cooling penalty will be.

    I suggest contacting a certified radon mitigator to discuss other solutions such as a "Sub Slab Depressurization System" - this is the most cost effective way to solve most radon problems. Every unit of the condo may not need a system. Careful testing & a good system design "may" solve the building's problem with a single fan & multiple suction points. Don't accept a quote over the phone & require a site visit from the mitigator because this is more complex than a single family dwelling.

    Check with your Sate Dept. of Health to speak to the Radon person to find out local radon issues & find a certified mitigator.

    Good Luck!

  6. Riversong | | #6

    If a "certified radon mitigator" thinks dilution is a solution to what is a carcinogenic problem even at the EPA "action level", then what this person needs is someone with more experience and common sense and fewer bogus "certifications".

  7. Tony Kiburis, NH Radon Mitigator | | #7

    This is a revised answer after I reread the original question & saw you had a high rise situation. (See answer #5.) A good mitigator will have to investigate your situation carefully which means testing multiple units & multiple floors to determine the source(s).

    HRV's or ERV's will work as a radon solution for low levels of radon (say up to 7-8 pCi/L) only. Higher levels of radon require too much air exchange to dilute the radon to levels below the EPA Action Level of 4.0 pCi/L. The higher the air exchange level the higher the heating or cooling penalty will be. However in a high rise they may need to be a part of the solution.

    High rise buildings that have radon on upper floors may have a out of adjustment HVAC system drawing radon via improperly sealed cold air ducting which draws the radon laden air from the basement & distributes it to the upper floor. Elevator shafts can be a pathway to bring radon up to resident's levels.

    Careful testing & a good system design "may" solve the building's problem with a single fan & multiple suction points. Don't accept a quote over the phone & require a site visit from the mitigator because this is more complex than a single family dwelling.

    Check with your Sate Dept. of Health to speak to the Radon person to find out local radon issues & find a certified mitigator.
    FYI, there is a great mitigator in Pennsylvania named Bill Broadhead who I know have experience dealing with high rise radon issues (he taught the course I attended on the subject). Call the State of Pennsylvania Dept of Health, radon Group They can put you in touch with him.

    Good Luck!

  8. Tony Kiburis, NH Radon Mitigator | | #8

    Re: Comment # 6. Yes, the EPA sometimes says: "The solution to pollution is dilution".

    The use of HRV's & ERV's is a valid technique to reduce low levels of radon!

    They are not the most commonly used technique. Their use is described & was first governed by the EPA Document, "Radon Mitigation Standards", (EPA 402-R-078, Revised April 1994). para. # 14.8 HVAC Installation Requirements.
    Currently the ASTM International Standard E-2121, "Standard Practice for installing Mitigation Systems in Existing Low-Rise Residential Buildings", para. # 7.3.15 Heat Recovery Ventilation (HRV) is the governing document for the mitigation industry. Under Note 4 of E-2121 it states: "HRV as a method for radon control is recommended only when an active soil depressurization system cannot be used, and the initial air exchange rate is low enough to indicate a high probability of success".

    Please contact your State Radon Office or speak to a Certified Radon Professional if you have any doubts about blog based radon comments.

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