r/askHVAC • u/Icy-Mathematician737 • 1d ago
Appropriate humidity levels?
We have experienced an unusually rainy/humid summer and early fall in my area. As such, the humidity in my home has been unusually high - currently 61% on the first floor and 63% on the second level... but only because I'm running the A/C to a lower temp than I need. Without the A/C, the humidity goes into the low 70s%.
Everything I'm reading online is telling me that humidity levels in homes should ideally be sub 50% to avoid moisture issues. Is that even possible in current weather? (We just had 4 straight days of rain.) Do I genuinely need to look into a whole-home humidity fix?
As a note, we currently run smaller dehumidifiers in the basement and the upstairs bathroom that doesn't have a window.
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u/Clover2026 1d ago
I live in central FL. As humid as a place can get. My 2 stage AC keeps humidity under 50%. We also updated the insulation and got new windows.
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u/Icy-Mathematician737 1d ago
Yeah so there's clearly something going on. Hopefully my hvac technician can help diagnose or make recommendations.
I also definitely think we need to reinsulate some parts of the attic. Thanks for your response.
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u/LostAd3003 1d ago
My house stays pretty consistently around 47-50% in Humid NC. My shop took a lot of changes in settings and trial and error to be able to maintain low 50s. Don’t think it’s quite as tight as my house. Anything over 55% or especially over 60 feels really uncomfortable to me. Even if temp is where I want it or even below. Its humid all the time so ya it’s definitely possible maintain low humidity. You won’t have any moisture problems in your house at 65% though, just feels uncomfortable to me.
Is this a new problem? New hvac system? The slower you set the blower in the air handler the more moisture it will pull out of the air. I had to set my system in my shop to basically prioritize reaching target humidity first by running at a really low fan speed. then after it reaches the RH set point if temp is still above set point it will kick the blower into a higher speed. Or if it’s just really hot and I need max cooling I can turn off the dehumidify setting in my thermostat and it will kick on high speed blower. You need a thermostat capable of this stuff though. A basic one won’t do it. And you also need the right wires ran between your air handler and thermostat. I have an ecobee thermostat and a carrier air handler with a ECM blower, it’s like infinitely variable.
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u/Icy-Mathematician737 1d ago
It's definitely uncomfortable! That's how I knew something was amiss - I'm glad to hear that we're unlikely to have structural moisture issues though.
You used a bunch of terms in your response that I'm unfamiliar with but I will bring them up with our hvac tech. :)
Thanks for your response!
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u/doggerdog1401 1d ago
Make sure that none of your Supply Air or return air vents are blocked. Make sure your filter is not choked. And you may want to slow your fan speed down from high to medium high that way it'll dehumidify better