2nd Floor Humidity too high

Discussion in 'HVAC Heating & Cooling' started by The Blur, Jul 15, 2016.

  1. The Blur

    The Blur New Member

    Jul 12, 2016
    New York
    My house is open design, from 1st floor to 2nd floor. The humidity is always higher upstairs, that it is down stairs. We recently removed the 3 ton unit from upstairs, and installed a 2 stage 2 ton unit. And the humidity is still a problem !! It's definitely not over sized now. Especially since it runs in 1st stage most of the time.

    The attic is insulated with R30.

    Does Humidity in a house tend to gravitate upwards ? I know in a basement, it comes up from the grade, and rises up. But I'm thinking humidity just keeps on rising & rising, and collects on the 2nd floor.

    How else can I reduce the humidity on the 2nd floor?
  2. Smooky

    Smooky In the Trades

    Apr 4, 2011
    North Carolina
    Do you have good exhaust fans in the bathrooms? Do you use the exhaust fans? Does the kitchen exhaust vent to the outside. Does the dryer vent to the outside? I would make sure they are working and venting to the outside properly. What kind of signs of humidity are you seeing?
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  4. WorthFlorida

    WorthFlorida The wife is still training me.

    Oct 28, 2009
    Orlando, Florida
    Humidity takes to the air like a sponge. It does not raise or drop. It moves from wet to dry air. When you have the high humid feeling, what is the temperature and do you have a read in the humidity level? If you set the temperature down too low and as the air gets colder, it's harder to dehumidify.

    This little monitor is pretty good and cheap. I bought a few of these to (https://www.amazon.com/AcuRite-0061...TF8&qid=1468680163&sr=8-3&keywords=humidistat) and used them to keep an eye on the humidity. It has an icon to tell you if the humidity is too low or high as compared to the temperature. Put a few of these around your home. It also be good in the dry winter months when you may be running a humidifier.

    If you have a shower on the second floor install a timer switch for the bathroom exhaust fan. Let it run about 15 minutes after running the shower to pull excess moisture out.
  5. Dana

    Dana In the trades

    Jan 14, 2009
    If you have high rates of air infiltration in the upstairs, outdoor air becomes a significant source of humidity during the stickier summertime days. In an air conditioned house the "stack effect" runs in reverse during the summer, with heavier cooler air leaving via leaks at the bottom half of the house, pulling in the lighter outdoor air from leaks in the top of the house. If you air seal both the attic and the basement it interrupts/impedes the stack effect flows, and the humidity should even-out.

    If the air conditioning ducts are in the attic, outside the pressure boundary of the house, leaks or duct design imbalances can drive very high rates of air infiltration independent of stack effect flows, with the exit & entry points more dependent on the duct supply/return imbalances than any other factor. But here again, air sealing the house (and the ducts) makes the biggest difference.

    Find an insulation contractor who specializes in air sealing for an assessment/quote. The first $1000-1500 of blower-door & infra-red imaging direct air sealing will typically pay for itself in 3-5 years on the heating bills alone in any NY location (but pays for itself in enhanced comfort immediately.) I haven't looked lately , but there are probably NYSERDA rebate subsidies available for that sort of work too.
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