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  1. #1
    Join Date
    Jan 2019
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    House with very low humidity

    Looking for some advice. We moved into our house 3 years ago and have noticed the winters are extremely dry in our house. Levels are showing up between 10%-20%. House was built in 1975, 2400 sq ft. We have baseboard radiant heating. have central air, dual zoned - an air handler in our basement and attic. I have tried room humidifiers, and I have tried large "whole house" free standing humidifiers with little success. I have been getting various responses from local companies. Some have suggested to attach and evaporator humidifier to our first floor air handler and run the fan. Others have said, not to do the evaporator, and use a steam humidifier connected to the handler. And yet others have said to use a ductless humidifier such as Aprilaire 360.

    I'm very torn on what to do. I feel like a humidifier connected to the ducts would disperse the humidity better, but I am concerned about only running the fan in the winter. I feel like it would be an energy suck by pumping cold air from the basement into the rest of the house, and then needing more heat. Also, since there would be no heat running through the ducts, would there be a concern for condensation or mold growing in the ducts?

    For the ductless system, my concerns are will the humidity really be able to disperse through the house, or only the room that it is pumping into? And how loud are the fans?

    Can anyone provide and insight? Has anyone used the Aprilaire 360 or the 865 model (steam w/ fan)?

    I appreciate any help - thank you!

  2. #2
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    Basics are that if it is 20^F,64%, a 10^F dew point outside, this infiltrating air being heat to 70^F, will drop to 10%RH without any moisture being added. To purge indoor pollutants and renew oxygen, most suggest a fresh air change every 4 hours. A 2,500 sq.ft. home may need a 100 cfm of fresh air when occupied. If we had 4 occupants adding .25 lbs per hour per occupant, 1 lb. per hour, expect 24% RH after everything balances out. Adding 1 more lb. gets you to 38% RH. So if your home leaks a 100 cfm with above which minimum for a pollutant level home, you need 2 lbs. per hour of humidification.
    By humidifying at a known rate you could figure out the air leakage rate of your home. A hot plate with a boiling pot could do provide a specific amount of moisture per hour. Using the outdoor dew point and the indoor dew point, the air change rate could be calculated.
    Or you add moisture until you get the desired result.
    Most humidifiers do not pass enough air through the wet pad to get the need evaporation. A large through the wall humidifier with 200 cfm of real air flow at 70^F entering will evaporate 2-4 lbs. per hour.
    Keep in mind that when the wind blows and the clothes drier operates, you may have 200 cfm of outside dry air passing through the home. Also, sudden changes in the indoor %RH cause the materials in your home to absorb or dry to the air in the home. All of this complicated to best of us.
    Keep adding moisture to the home until you get what you want.
    Drying clothes in the home will do the same thing as boil pot.
    I would bet biggest evap pad humidifier with plumbed water supply I could find.
    I would avoid electric steam.

    https://www.aprilaire.com/whole-hous...fier/model-360

    https://www.amazon.com/Aprilaire-Pow...41109055&psc=1

    Keep us posted.
    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"

  3. #3
    Join Date
    Jan 2019
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    Thread Starter
    Thanks for the reply and info! I have a couple questions.

    Would the Aprilaire 700 work with an air handler? From what I have read I would need hot air to evaporate the water from the wet filter pad? Why would you avoid the steam models?

    Also, any ideas at what could be causing an air leak? It's an older home, but we put in new windows and doors w/in the past year. We also added insulation to our attic. Could our fireplace be the cause? We keep the flue closed, unless we use it.

    Thanks again!

  4. #4
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
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    Quote Originally Posted by Kevbo View Post
    Thanks for the reply and info! I have a couple questions.

    Would the Aprilaire 700 work with an air handler? This unit is design for an air handler and would require the blower to be operating.
    From what I have read I would need hot air to evaporate the water from the wet filter pad? Not true, dry air is required. warmer aif evaporates more moisture.
    Why would you avoid the steam models? Using electricity is 3X more cost than heat pump or Nat gas. All of the steam units are problem prone. Air flow through a wet pad will get a lot of moisture into your home. I would also avoid hot water feed because of cost and minimal effect. Figure out how to get 200 cfm of house air through a large humidifier. You will be amazed at the results.

    Also, any ideas at what could be causing an air leak? It's an older home, but we put in new windows and doors w/in the past year. We also added insulation to our attic. Could our fireplace be the cause? We keep the flue closed, unless we use it.
    All homes leak during wind and cold outside air. You need 100 cfm of infiltration to have good air quality. Figure out how to get 2-3 lbs. of moisture into the home, that is enough moisture to humidify 100 cfm of fresh air. If not moist enough go after the air leaks. Seal rim joist area and ceiling/attic connections with foam


    Thanks again!
    Homes leak during wind, cold weather and need ventilation during calm mild weather.
    Keep us posted.
    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"

  5. #5
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    18,297
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    Start with a Blower Door Test to find all the air leaks in the home.

    A 70's home will surprise you how many there are!

    Once there identified you can plan a course of action for the repairs!

  6. #6
    Join Date
    Apr 2003
    Location
    St. Louis
    Posts
    818
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    Steam humidifiers will put lime into the air stream just depends how hard your water is.

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