Radon in a mixed-use multifamily high rise

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.

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

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.

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!

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".

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!

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.