Will Radon Mitigation System Lower Humidity
We got a great question, “Will Radon Mitigation System Lower Humidity?”, on our Ask A Ninja page from Douglas in Carson City, Nevada.
I am having my home mitigated for radon. The level is a 3.9, under the 4.0 recommendation for mitigation, however I am doing it anyway.
There will be an ASD (active soil depressurization) system installed, followed by a vapor barrier. I read an EPA study that stated ASD was by happenstance greater overall at dehumidifying a crawl space because it was pulling the damp soil from underneath the vapor barrier, which left little humidity to permeate the vapor barrier.
If ASD is able to do this, is a dehumidifier needed? If in fact this ASD system is more efficient at dehumidifying then for the 2k cost of installing and materials, could it be a better fix or an added fix? My house is in Carson city NV, I am not in a flood zone and the humidity is low compared to the rest of the country. My certified radon contractor is open minded and I’m glad I found him, but it doesn’t seem that radon contractors coordinate with experts like yourself when installing vapor barrier.
I asked him if he was planned on sealing the vents, he said no. So we had a discussion and he said he would. Also he was only going up the exterior wall about a foot, but would go higher up the wall with vapor barrier upon my request. Let me know your thoughts and if I indeed need a dehumidifier anyway, on top of the ASD. THANKS!
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Is Dehumidifier Needed with Radon Mitigation
Douglas, I want to applaud you for installing an Active Soil Depressurization system in your crawl space even though your radon levels are below the 4.0 picocuries per liter, or pCi/L. We feel radon levels should be as low as possible in every home.
I created a link to an EPA study above and hopefully it is the same study you read and referred to in your question. I do want to be clear before we get into the subject matter that dehumidifiers do not remove radon but according to the EPA study, an ASD can control humidity.
I cannot argue with the findings on the EPA as we have seen radon mitigation levels control humidity in both basements and crawl spaces. The problem lies in the improper installation of the system, it degrading over time and the relative humidity found outside. Homeowners like yourself can trust but verify what contractors tell them. I have no doubt your contractor is telling you the truth, but every home and region is different.
For example, you mentioned the relative humidity in Carson City, NV is low compared to other areas. This may be true but according to USA.com the average relative humidity in Carson City is 78.98%. This is very high when it comes to damage that can occur via mold and fungus growth from high humidity. My point is an improperly installed or degraded ASD can eventually pull in that 78.98% humidity. I recommend a humidity reader after the ASD is installed to verify the humidity levels on a constant basis if you do not install a dehumidifier.
Should the Vapor Barrier Cover Most of the Wall
I think you should have your contractor take the vapor barrier all the way up the wall. If your state requires a termite gap, be sure to abide by local codes. The vapor barrier up the wall will help minimize moisture from rain and humidity. This should allow the radon fan to work even better at keeping the humidity low.
Sealing the vents may have an effect on the radon fan but if the ASD is installed and sealed correctly there will be very little air movement above the vapor barrier. When the vapor barrier is installed it is sealed with polyurethane caulk to prevent air movement except under the vapor barrier. You may decide to add a foundation vent fan blowing out in order to make sure the air above the vapor barrier is not entering your home.
Best Humidity Level for Crawl Space
Can a Radon Mitigation System Raise Humidity
While researching information about your question, I came across an inspector that concluded the radon fan was actually raising the humidity levels in a home. This is why I say all homes are different and humidity levels should be checked to ensure what your ASD is doing. I found the information on the Green Building Advisor Community and Q&A. He said:
After documenting the temp and RH in both the house and crawl space, I have discovered the Radon Fan is somehow bringing humidity (outdoor air) into the building envelope.
Here is a link: https://www.greenbuildingadvisor.com/question/radon-fan-causing-increased-humidity
In conclusion, I would wait on installing the dehumidifier until you measure the humidity after the ASD is installed. Great question and hope that helps.
What Next?
Do you need help with mold removal, crawl space encapsulation, crawl space insulation, vapor barrier, waterproofing, foundation repair, or controlling humidity in your crawl space and you live in Georgia, Delaware, North Carolina, South Carolina, Tennessee, Ohio, or Kentucky? If so, please contact us to schedule your assessment. Also, let us know in the comments below if you have an idea for a new blog topic.
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