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  1. #1
    Join Date
    Jul 2005
    Phoenix, AZ
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    Winter Humidity In Apartment

    Hello, I am looking for some expert advice from indoor air quality experts here in the forum. I have an apartment complex that was converted from a resort to apartments. The buildings are concrete construction built in the late 80's. The apartments have old style single pane glass windows. The load bearing walls are concrete. Thr non-load bearing walls are drywall and metal studs. With insulation. The lid is 6" of concrete between floors and the ceiling as well. The HVAC system installed are old style Red "T" Coil units. They are 2 to 2-1/2 ton cooling split systems with strip electric heat. The bathrooms have one standard vent fan with lights controlled by a switch. The problem is excessive winter humidity. It is so severe that the walls condensate and create black mold in the corners and especially on all the window sill ledges. Previous management has tried to install Broan humidity sensing fans with sensors in the bath vanity, kitchen, and in front of the small laundry areas to remove humidity. The previous management has been treating the surface mold on the walls and sills. My question is; what is the best approach to resolve the humidity issue knowing the type of construction. Are the humidity sensing fans the way to go? I am looking for some expert advice.

  2. #2
    Join Date
    May 2004
    south louisiana
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    the problem is the concrete block is seldom insulated so that ambient temps
    transfer through them easily.
    with metal studs in interior walls you have another product that
    transfers temps well.

    I'd start out with a stand alone dehumidifier & see how much that reduces
    RH in the apt.
    put some RH sensors and record RH morning noon evening & night.
    then run dehumidifier.
    if this brings RH down, then you have your answer.

    when RH is 50% and mold, mites etc

    given that you have such conductive materials..
    sizing the hvac system & putting whole house dehumidifiers
    woule be a good investment. and may well be what you need
    to do.

    other things to look at would be how to insulate the block walls.
    installing windows that don't conduct temps.

    I lived in a house with concrete block walls & stucco like finish to
    interior. after one winter with condensating walls & mold on
    box springs & sofa touching exterior walls...I moved.

    I realize that isn't an option, just saying now...I often think about that
    house & wonder what they were thinking!

    pm teddy bear...& send link of your thread.
    he is great with all climates & can give you more specific
    dehumidifier advice. I'm still learning from him in this area.

    best of luck.

    best of luck.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  3. #3
    Join Date
    Jun 2003
    Madison, WI/Cape Coral, FL
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    Assuming an arrid climate like the SW and more of a winter problem, focus on the inside temp/%RH/^F dew point. You inside dew point must be 10-20^F below any inside surface temperature. Heating the space 24/7 helps keep the inside surface temps warm. When outdoor dew points are 10-15^F lower than the desire inside dew points, moving the dry air through the building is the most cost effective method of reducing indoor dew points.
    Exhaust or make-up air ventilation at an air change in 4-5 hours should remove occupant generated moisture from inside the space. If not increase the air flow. Also ventilate 24/7 until the indoor dew points decline to near outdoor dew points. It is also critical to maintain heating inside to warm the inside surfaces where the mold is occurring.
    Dehumidification should be used when the outdoor dew points are +55^F and the cooling load is not adequate to dehumidify the space. A proper setup a/c should have a cold coil that is -30^F colder than the a/c return temperature to max moisture removal.
    All occupied space should have an air change in 4-5 hours when occupied regardless of the outdoor dew point. This is to purge indoor pollutants and renew oxygen.
    Monitor indoor Temp/%RH/dew points, operate exhaust fans 24/7 until moisture is reduced. AZ outdoor dew points are currently 20-25^F. This is drier air than a dehumidifier can prodcue. When the outdoor dew points rise to +50^F, dehumidifiers are critical to lower indoor moisture from occupants and critical fresh air ventilation. Operate your ventilation on a occupancy bases with enough volume to change the air in 4-5 hours. If you have high occupancy or excess moisture generation, increase the air change rate.
    Hope this helps. Provide the actural indoor temps/%RH/indoor dew points for more help.
    Any inside water leaks or cloths drying complicate the problem.
    Regards TB
    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
    Join Date
    Dec 2011
    New Zealand
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    There are generally 2 issues with damp buildings.
    The first one is the building and it contents, are themselves full moisture. When add heat to dry the air (not really drying but changing the RH or the ability to absorb moisture), you normally get a flush, normally seen as condensation on the windows, at this point many stop, because they believe the problem is becoming worse, as you can see more evidence of water. You have to go through this point.
    When this is achieved follow Teddy bears advice, this will fix the second issue of a build up in the future.
    If the ambient drops below 6C and you have single glazed windows, it should not be un-common to see a condensation forming, as air that is to dry is equally as bad as air that is to damp.

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