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  1. #1

    Humidity control help

    Hello I've been lurking here for a while but finally decided to post my question. I know most of my questions have been answered on other threads but possibly as a result of information overload I feel a bit stuck. I have a 2 part question all relating to controlling the humidity in my home.

    I have a 2 story house with a basement. I have a Lennox power whole house humidifier, HVAC company installed, in the supply above my furnace. For obvious reasons I'd like to move it but since we're hopefully nearing the end on the humidifier season I'll investigate that later. To minimize my families indoor allergies and installing engineered hardwood floors maintaining the RH is at the top of my list.

    1) I'm looking for a thermostat that includes automatic humidity control. Currently my humidistat is installed in the return air duct in the basement, out of sight out of mind until I have 1/4 inch of ice on the inside of my windows. Any recommendations on a unit, or pros/cons of moving the humidistat to the main level? Should I keep them separate, and does it matter where the humidity measurement is taken as the basement tends to be more humid? For some reason humidity control does not seem to be included in thermostats until you get to the higher end which might be more than I need.

    2) Now on to Dehumidification. 2/3rd s of my basement is finished, the unfinished side has my furnace, air handler, water heater, and water softener. On the finished side I have an enclosed room maybe 4ft x 4ft that has ejector pump and sump pit. I have had minor mold issues in that room usually controlled by using damp rid desiccant buckets and cleaning the walls with bleach, but inevitably I forget to dump the buckets. While during the summer the basement humidity seems higher than the rest of the house, it does not have that damp musty mold smell, but there is mold that I'd like to eliminate. I want to buy a dehumidifier for that room only as that is the main source of moisture in the basement. I was thinking about a 50 pint Frigidaire model # FAD504DWD. Being that the room is totally closed, obviously it would control the humidity in that room, but how much would it do for the rest of the basement, or is that overkill for one room? I'm not opposed to installing a vent fan to move some air or even removing the ceiling in that room to open it up a bit. Any thoughts on that type of situation, I'm not sure I need a whole house dehumidifier as the main problem is only that room.

    Well I think I've rambled enough, Thanks in advance for any suggestions.

  2. #2
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    Is it an open sump pit, or is it covered.
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  3. #3
    Sorry, it's covered.

  4. #4
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    I would think a 50 pint would short cycle in a 4X4 room. Might need to add a supply and return to the room. Or an exhaust fan to get rid of the air in the room.
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  5. #5
    Join Date
    Apr 2010
    Location
    Winnipeg,Manitoba,Canada
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    What type of hardwood floors do you have. There are only a couple that actually require higher humidity. Usually installed in the more tropical areas.
    The type of windows and outdoor temperature along with the RH% inside the house have a bearing on what the RH% should be at.
    Is this a newer house ? Is the basement spray foam insulation or batting ? Are there any cantilevers. I have found most mould is in these.
    Do you have an HRV and or central exhaust system ?

  6. #6
    @beenthere, The cycling dehumidifier was a concern for me as well, I was also thinking a 30 pint, but was worried about it never shutting off. As I said the sump is covered but not sealed, which might be a question for another board. I'm pretty confident that is the main source of moisture. I'm leaning on going with the 50 and see how it cycles with the door open and closed then decide on a fan and return as you suggested.

    @ryan, no hardwoods installed yet, possibly this spring but would like to get dehumidification under control. Currently I'm looking at engineered hickory It would be on the first floor so moisture coming from the basement would be a little concern but a good vapor barrier would take care of that I think. We live in the Midwest so RH extremes are common. The house is 7 years old, not as tight as it probably should be considering its age, and since getting involved in my HVAC system I'm noticing a lot of leaky ducts. The basement has fiberglass batting insulation on the finished side and the wall that splits the unfinished side (not sure I'm explaining that right) in the unfinished side no insulation on the walls but the rim joist has fiberglass batting, which I'd like to change over to sprayed foam, in fact I'd like to do the whole unfinished side with spray foam but one thing at a time. No Cantilevers and no heat recovery, exhaust or fresh air vent system as of yet. I would like to at some point but haven't researched any of those as of yet.

    Thanks for the replies!

  7. #7
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    Quote Originally Posted by shess757 View Post
    Hello I've been lurking here for a while but finally decided to post my question. I know most of my questions have been answered on I have a 2 story house with a basement. I have a Lennox power whole house humidifier, HVAC company installed, in the supply above my furnace. For obvious reasons I'd like to move it but since we're hopefully nearing the end on the humidifier season I'll investigate that later. To minimize my families indoor allergies and installing engineered hardwood floors maintaining the RH is at the top of my list.
    Well I think I've rambled enough, Thanks in advance for any suggestions.
    Where are located? number of occupants? Real %RH/Temps winter and summer? Amount of fresh air? Do you want real indoor air quality?
    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"

  8. #8
    Join Date
    Apr 2010
    Location
    Winnipeg,Manitoba,Canada
    Posts
    128
    In the newer homes here codes have changed. All homes require HRV's due to the moisture from the building materials. Extreme weather in our area to. Summer can be 95+F and 100%RH Winter is -40F and below for several weeks with low RH%. The problem with homes without the HRV's and just a central exhaust is all building materials are still drying and that moisture has no where to go due to the tightness of construction and high efficiency furnaces.
    There are some great articles that have been published in our area due to this common problem.
    It all hinges on what your ambient air outside is corresponding to the indoor air and RH%.
    Recommendations. Put in an HRV and interlock it to a central exhaust system/furnace. Spray foam would help greatly. I reused the insulation from the basement and put it into the garage. Have about the same aged home and had a lot of the same problems. HRV seemed to solve many of our problems. We just put laminate flooring in that looks like hardwood. Then I don't have to worry about it drying out. And the wife likes the look too !

    Check the local codes.

  9. #9
    @TB located in Indianapolis, 2 adults 3 children and 2 dogs which does not help with air quality, but I'd go before the dogs! We generally keep thermo around 70 in winter and 76 summer, I'm sure those don't translate to actual temps and obviously there is a pretty big temp difference between floors. Humidistat is not accurate at all I usually adjust it up when we start shocking each other and back down when I start to notice moisture on the windows. The problem with that is if I'm not around to adjust it. We also use a gas insert fireplace during the day in the winter, which throws another issue in the mix. I have humidifier set up to run when the blower is on which we leave on. From what I understand that isn't the most efficient way for the humidifier but our furnace may not kick on during the day due to the gas insert that's the only way I can think of to add some humidity. As for fresh air during the winter probably not enough, some rooms are drafty but no fresh air vent. As for air quality obviously I want the best for my family, at a minimum reduce our indoor allergies, stabilize the humidity, and eliminate the mold in the sump room.

    @ryan, I didn't think about the house itself still drying out, I suppose over the years I have noticed the humidity getting better but still needs managing. I'm wanting to get rid of the carpets to further reduce allergies, we decided on engineered hardwood I guess less sensitive than real wood but more than laminate. Spray foam is definitely on my to do list, but I'll start reading up on an HRV.

    I also have ceiling fans in all rooms on the second floor that are on year round which I change directions in spring and fall.

    Thanks!

  10. #10
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    I would cover the sump with Plastic. Basements in your region need dehumidification during 3 seasons of the year. Place a simple temp/%RH meter in the space and confirm the %RH is <50%RH.
    Actually to optimize the indoor air quality in room, you should an air change in 4-5 hours when the home is occupied. You probably are getting adequate air change during cold windy weather. During calm moderate weather, most need supplemental fresh air ventilation to purge indoor pollutants and renew oxygen.
    Set the humidifier at 35%RH. Should be ok in the cold air return.
    Spring/summer/fall is a different problem. When the outdoor dew point is +55^F, you need whole house dehumidification. During high cooling loads, the a/c will maintain <50%RH. During low/no cooling loads and +55^F outdoor dew points, the whole house dehumidifier will maintain <50%RH. Fresh air change, <50%RH, will maintain the best of indoor air quality in your home. <50%h is the key to eliminating mold and dust mites, which are the most common allergens in a home.
    The whole ventilating dehumidifiers like the Ultra-Aire are simple fixes for this 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"

  11. #11
    Are you suggesting to completely seal the sump pit? I do have a plastic cover on it now but its not airtight by any means. I would like it to be sealed but I'd need to figure out some type of vent, I'm guessing there would be a negative pressure when the pump runs, but then again the drains are open.

    I do need to measure the actual RH to see exactly what I've got, as for the sump room I just assumed it was higher than 50% due to the mold growth. Seeing that I have several more options I'm really spinning from information overload!!

    What is the main difference between an ERV and a whole house humidifier such as the Ultra-Aire? And would either of those units help with the sump room being that it is basically closed off from the rest of the house? I guess I'm wondering if I get and ERV or house dehumidifier, would I also need something for that room?

    Any recommendations as far as a thermostat/humidistat/ventilation control? I'd like everything in one unit as I don't think having a three different controls on my wall would go over too well. perhaps the higher end units I originally thought were overkill might not be now.

    Thanks again for the suggestions!

  12. #12
    Join Date
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    Location
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    Quote Originally Posted by shess757 View Post
    Are you suggesting to completely seal the sump pit? I do have a plastic cover on it now but its not airtight by any means. I would like it to be sealed but I'd need to figure out some type of vent, I'm guessing there would be a negative pressure when the pump runs, but then again the drains are open.

    I do need to measure the actual RH to see exactly what I've got, as for the sump room I just assumed it was higher than 50% due to the mold growth. Seeing that I have several more options I'm really spinning from information overload!!

    What is the main difference between an ERV and a whole house humidifier such as the Ultra-Aire? And would either of those units help with the sump room being that it is basically closed off from the rest of the house? I guess I'm wondering if I get and ERV or house dehumidifier, would I also need something for that room?

    Any recommendations as far as a thermostat/humidistat/ventilation control? I'd like everything in one unit as I don't think having a three different controls on my wall would go over too well. perhaps the higher end units I originally thought were overkill might not be now.

    Thanks again for the suggestions!
    A leaky cover on the open sump will isolate the moisture to the sump. A vent on the door or wall of the small space will allow any escaping moisture to equalize. You will have as much of problem with the moisture in the basement condensing on the cool surfaces of the sump room. Keep the basement will <50%RH and the sump room will be ok. The real moisture source is from the outside air when the outdoor dew point is +50^F and from the occupants. Tracking indoor %RH will illustrate the problem.
    You need a fresh air change in 4-5 hours when the space is occupied. This is about 100 cfm per 2,500 sqft. of space. It is not much and conditioning cost is <$1 per day on the worst days and nothing on the neutral days. The a/c will maintain <50%RH during hot weather. The humidifier will maintain +35%RH during low dew point days. The whole house dehumidifier will maintain <50%RH throughout the home on the days with high outdoor dew point and low/no cooling loads.
    The ventilating dehu option of the Ultra-Aire will mechanically provide fresh air when needed, filter, blend, and circulate it throughout the home.
    An ERV is an additional device that reduces conditioning ventilation air cost needed in the home. In home in most of the US that need little fresh air during the extreme cold weather, ERV do not have adequate pay-back.
    Because of this, the whole house dehu is good solution to fresh filtered air and maintaining <50%RH during days of high dew points and low/no cooling loads.
    Here is info on the general use of the ventilating dehu.
    http://www.thisoldhouse.com/toh/tv/a...eo/0,,,00.html
    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"

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