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  1. #1
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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!

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  3. #2
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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"

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  5. #3
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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!

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  7. #4
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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"

  8. #5
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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!

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  10. #6
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    Steam humidifiers will put lime into the air stream just depends how hard your water is.

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  12. #7
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    Air will leak through every electrical outlet, every switch plate, everywhere a plumbing pipe passes underneath the kitchen countercounters, every drain pipe through the floor.

    The air will enter in the ceiling plates where the romex wires enter the walls. The air will seep between the drywall and the studs. The air will seep in where the thermostat wires come into the thermostat. Yes lots of air will seep in through your closed damper in your fireplace. Ceiling lights, behind the kitchen cabinets, around your exterior doors-- air can be sucked into all those places if your house has a negative pressure.

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  14. #8
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    I live in a 3-floor townhouse with units on each side. My HVAC unit indoor is a Lennox C33-44c-2F (Merit Series) and the outdoor unit is 13ACC-042-230-01. My issue is the humidity is extreme in winter and summer Winter RH is usually 16-20% and Summer RH is usually 55-70%. During the summer, the house get very musty smell, and doors and cabinets don't close properly. In the winter, typically wake up with a bloody nose. Home is about 15 years old. I also was looking at some type of whole-house solution, but reading several post, sounds like I need to get blower speed and duct leakage checked. Any other suggestion that I should consider for that may apply to a townhome vs. a single family house? Thanks

  15. #9
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    In general an whole house humidifier can assist in adding humidity in the winter months. The effectiveness of a whole house humidifier will of course be contingent on the actual effectiveness of your current supply and return ducting systems along with proper sizing and the installation of the humidifier system. If the ducting system is inadequate, especially with three levels, the physics on convective air currents with be your enemy in the delivery of the added moisture. As far as de-humidification goes I like the constant torque blower motors that come with furnaces and air handlers alike. The only caveat with these systems is that they only dehumidify if there is a demand for cooling. Of course you can also install a whole house de-humdifier but the same issues with the three levels and ducting system applies just as in the heating cycle. With the cost of whole house humidifier and de-humidifier being substantial you definitely would want to ensure you have a top rated company perform the work. If the ducting is inadequate realize that changing it will be and endeavor that takes patience. Although, a properly installed HVAC will create an environment in your home that is extremely comfortable for your family. Good luck.

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  17. #10
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    Quote Originally Posted by swdtech View Post
    In general an whole house humidifier can assist in adding humidity in the winter months. The effectiveness of a whole house humidifier will of course be contingent on the actual effectiveness of your current supply and return ducting systems along with proper sizing and the installation of the humidifier system. If the ducting system is inadequate, especially with three levels, the physics on convective air currents with be your enemy in the delivery of the added moisture. As far as de-humidification goes I like the constant torque blower motors that come with furnaces and air handlers alike. The only caveat with these systems is that they only dehumidify if there is a demand for cooling. Of course you can also install a whole house de-humdifier but the same issues with the three levels and ducting system applies just as in the heating cycle. With the cost of whole house humidifier and de-humidifier being substantial you definitely would want to ensure you have a top rated company perform the work. If the ducting is inadequate realize that changing it will be and endeavor that takes patience. Although, a properly installed HVAC will create an environment in your home that is extremely comfortable for your family. Good luck.
    This a good post. An HVAC system should include a whole house humidifier and dehumidifier. An Ultra-Aire 70 H connected to the a/c ducts a ideally adjusted a/c will take care of the mild seasons and maintain <50%RH.
    To test for humidification, try adding a specific amount of moisture to the space by hanging a wet bedsheet in the warmest part of the space during heating.
    Wet the sheet in a known amount of water. Like wet in a small pail of water, measuring the amount of water the sheet soaks up. Hang on stretched cord until dry. Measure the increase of the %rH on the space. Note the outdoor dew point and wind mpH. This will give us a rough estimate of the air leakage and size of humidifier need. I just come up with this, any better ideas, like a hot plate boiling water in the space or a water mister/fogger and measuring lbs. of water per hour to raise the %RH in the space.
    Anyother ideas?
    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"

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  19. #11
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    I have a big house and with time problems started, as the air is very dry. Also, there were problems with sleep, I had to constantly go to drink as the whole throat was dry.
    I personally made the decision from 4 main factors:
    1) How often will I have to clean it ?;
    2) Lifetime, because I want not to go too far beyond the budget, but also not to buy a new one, say, every year;
    3) What will be the water supply? My friend bought several humidifiers and now he poured water in there at least 2 times a day, which does not suit me;
    4) Will there be a connection with my thermostat?
    This site helped me, look at the information there, I think it will solve your problem.

  20. #12
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    Quote Originally Posted by servicefitter View Post
    Steam humidifiers will put lime into the air stream just depends how hard your water is.
    Why? It's just water vapor.

  21. #13
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    Cool mist humidifiers require a good air filter down stream to remove the solids left in the air after evaporation of liquid water. We are talking high merv filters +11. Steam humidifiers leave the gunk in the tank.
    Distilled water has no solids and eliminates the need for an air filter down stream.
    A normal 2,500 sq.ft. home need 80 cfm of fresh when occupied to purge indoor pollutants and renew oxygen. In a cold climate with <20^F winter dew point, needs 3-4 lbs of humidification per hour to maintain 35-40%RH inside. Four occupants may add 1-2 lbs per hour. You need an additional 2-3 lbs. of moisture from a humidifier to be comfortable. You can not tighten up a normal home enough to have comfortable %RH and be healthy with out humidification.
    Same goes for summer in a green grass climate. You need +4 lbs. of dehumdification per hour to maintain <50%RH with an outdoor dew point of 70^F and 80 cfm of fresh air ventilation. Where do you guys come up with this tighten up the home and it will be good stuff.
    Tighten the home up and provide 80 cfm of fresh air change with enough humidification to maintain 40%RH during cold weather and enough dehumdification to maintain <50%RH during mild season high outdoor dew points is good advice.
    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"

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