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  1. #1
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    Oct 2018
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    High Humidity in apartment, what's wrong?

    Live in a nice, new apartment complex. 750sq ft. 2 bedroom. Place was built 3-4 years ago. 1st floor of a three floor building. My concern is that my Air Quality monitor shows 70% solid. Now, I have done my best to confirm this, I've bought two other handheld humidity monitors at Lowe's and Menards, and so now I have three devices reading the same thing. So the numbers are not due to a faulty device. Plus or minus a few, it's gotta be pretty accurate.

    All reading 70%, it's October right now. I know that's not too crazy high, but I have health problems and am worried about mold/mildew growth based off what my doctor is telling me.

    If I crank the air conditioning, I can get it down to 56%, but then it's freezing in here (80 outside now, nice fall day) and obviously expensive to run that constantly. I have a dehumidifier coming on order (70 liter, biggest I could get) that might hopefully help, but I'm not sure that's the solution. Doctor says I have toxin/mold issues. I know not everyone believes in that stuff, but I'm just looking for advice regarding HVAC and IAQ.

    Is this normal for a ground level apartment? My other apartment didn't have this issue (top floor, 5th floor city studio). Humidity was probably 40-50 there.

    Where is it coming from? I guess outside, it's 80% humidity out there here in Northeast Ohio, but what can I do? Hoping the dehumidifier works, just looking to gain a better understanding of what's going on from folks who know more than I. Would a 2nd or 3rd floor apt have been without this issue?

    Thanks in advanced to all.

  2. #2
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    The source could be infiltration or from occupants.

    People perspire, breathe, cook, shower, clean, etc. All of which introduce moisture. Most buildings have a stack effect - warm air travels up and out of the building at leaks so the lower level is under negative pressure which brings in outside air.

    Additionally, air conditioners are frequently too big for the space so they don't run long enough, even during peak load times, to dehumidify thoroughly. Your first floor apartment has very little load as you have conditioned space above instead of a hot attic as do the top apartments. I venture to say all the apartments have the same size air conditioner even though the loads are vastly different. That is the nature of apartment building and management.

    A dehumidifier is likely to be your best recourse.
    AOP Rules: Rules For Equipment Owners.

    Free online load calculator: http://www.loadcalc.net/


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  3. #3
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    Jun 2003
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    Crack a couple windows to get some fresh air. Set the dehumidifier for 50%RH.
    Keep us posted on the %RH after you get the dehumidifier working.
    Regards Teddy Bear.
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  4. #4
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    Which temperature do you have in the apartment? You can make the humidity lower with two simple ways.

    1. Most simple, open the windows and let to fresh air from outside go in the appartment.

    If you have inside 70% and temperature about 70 F (or 21 C), you take the fresh air with temperature about 57 Grad and humidity 70%. But in the apartment fresh air will be heat till 70 F and humidity of this air will turn to 46%. With the mixture with your inside air and outside air you'll receive about 55-60% of the humidity.

    2. Just make the temperature higher. If you have the temparature 70 F and humidity 70% - you can just make the temperature higher till 74 and the humidity will be sink till 62%, f.e.

    Generally, sometimes it could don't help. The problems can be in the high volume of the moisture that comes from outside (wet walls due to problem with the walls hydro isolation, f.e.) or inside (a lot of cooking, bath room without good ventilation, drying of the wet clothes in the room) etc.

  5. #5
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    Sep 2018
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    Florida
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    You need to do the following things in order to have a comfortable environment.
    1. Utilize the dehumidifier at 50%RH inside the interior portion of the house.
    2. Go for windows remodeling and have a number of ways in which fresh air can get inside without any inconvenience of daylight.
    3. Moreover, the humidity can also reduce with a warm environment temperature wise.
    In order to consult a professional contractor near your location, go on websites like Renovaten, Home Advisor, Mr.Handyman

  6. #6
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    Nov 2006
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    Quote Originally Posted by Andrew Agar View Post
    You need to do the following things in order to have a comfortable environment.
    1. Utilize the dehumidifier at 50%RH inside the interior portion of the house.
    2. Go for windows remodeling and have a number of ways in which fresh air can get inside without any inconvenience of daylight.
    3. Moreover, the humidity can also reduce with a warm environment temperature wise.
    In order to consult a professional contractor near your location, go on websites like Renovaten, Home Advisor, Mr.Handyman
    Seriously, Home Advisor? I think of it as Hack Central.
    AOP Rules: Rules For Equipment Owners.

    Free online load calculator: http://www.loadcalc.net/


    There = not here. Their = possessive pronoun. They're = they are
    It's = contraction of it is. Its = the possessive form of it
    Too = also. To = expressing motion. Two = 2
    Then = after that, next. Than = indicates a comparison.
    Questions should end with a question mark "?" Statements end with a period "."

  7. #7
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    Additional things to do to lower the indoor %RH.
    Check for the supply temperature/%RH verses the return temperature/%RH. You are checking for a humidity removal by the a/c. This is done by comparing the dew point in the space verses the dew point in the a/c supply we are looking a 5-7^F reduction in dew point. The lower limit is 50^F supply temperature (avoid freezing a/c coil). Reduce the air flow through your a/c to lower the coil temperature. MOst a/cs have a fan speed setting on the fam motor. Go for a lower speed setting. If needed, get the most restrictive air filter available.
    Operate the fan in the "auto" mode when trying to max dehumidification.
    Apartments general need a little fresh air. Most suggest a fresh air change in 4-5 hours to purge indoor pollutants and renew oxygen when occupied. Measuring CO2 is an accurate method of determining actual air change rate. CO2 meters are available from Amazon for 100 bucks.
    Get the dehu operating and set at 50%rh. Measuring the water from the dehu also is a way of estimating air infiltration. 25 cfm of 70^F dew point fresh air about 1 lbs. of moisture load per hour, if the space is maintain 75^F, 50%RH, 55^F dew point.
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  8. #8
    Join Date
    Oct 2018
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    Thread Starter
    Getting the dehumidifier today, will report back on how it effects things.

    I have a meter for co2 built into a device (awair, a little iaq monitor) and the co2 can get high sometimes in here, but that is also due to a gas range and gas stove. Nonetheless, we open the windows now after using the oven or stove because the levels often jump over 1000, or with the oven, co2 can get to 2000. When we run the ac, co2 seems to stay a little more stable but the stove and oven will mess that up regardless.

    Without the stove or ranges being used at All though, sometimes co2 will push 1000 anyway. Only two people living here but it's a new place, probably built pretty tight, that happens after being home all evening. Again, AC helps it maintain stability.

    Been running the AC just regular (set to 69F) have humidity at around 64% with it on at this comfortable setting, temp 69F indoor, (73 outdoor now). Still not good right?

    I will also take a look at the supply and return %RH, thank you for that bear.

    Thank you all again.

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