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  1. #1
    Join Date
    Jan 2013
    Posts
    24

    ERV vs. Whole House Dehumidier vs. ?

    Hello all. We have recently had some renovations to our home and would like to bring in more fresh air without introducing humidity. We live in east central Missouri with cool to cold winters and long hot summers. We do have some extremes in temperature. The average temp in January is 38 and in August is 88 (but it varies a lot from low to high, so the averages are a little misleading.) Summers tend to be humid. We would like something separate from the furnace/ac. Our house is small (not quite 900 square feet.)

    Would a whole house dehumidifier be too drying in the winter? We are a family with allergies and chemical sensitivities, and we feel better with low humidity, but we also don't want to have dry sinuses and/or ruin our furniture. Would an ERV bring in too much humidity for our area? We are stumped about what to do.

    Thanks so much.
    Pam in MO

  2. #2
    Join Date
    Jun 2002
    Location
    Dacula, GA
    Posts
    11,991
    Well if you have a real "tight" house then a stand alone dehumidifier will work best for the summer and you don't run it in the winter unless the humidity for some reason gets to high.

    I would get my outside air through a 3" duct from the outside to the return plenumn with a damper on it to set the amount. I would also get a unit from Carrier, Trane etc with a variable speed drive and a thermidistat to slow down the blower fan and load the coil up for maximum dehumidification.

    This alone may be enough to reduce high humidity in your house but definitely get it to use with a dehumidifier if you get one. A ERV is a very expensive way to go but is more energy efficient than just pressurizing your house by pulling in outside air to your return plenumn.
    "I could have ended the war in a month. I could have made North Vietnam look like a mud puddle."
    "I have little interest in streamlining government or in making it more efficient, for I mean to reduce its size. I do not undertake to promote welfare, for I propose to extend freedom. My aim is not to pass laws, but to repeal them."
    Barry Goldwater

  3. #3
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,060
    Quote Originally Posted by Pamp81 View Post
    Hello all.Our house is small (not quite 900 square feet.)

    Would a whole house dehumidifier be too drying in the winter? We are a family with allergies and chemical sensitivities, and we feel better with low humidity, but we also don't want to have dry sinuses and/or ruin our furniture. Would an ERV bring in too much humidity for our area? We are stumped about what to do.

    Thanks so much.
    Pam in MO
    Occupied space needs an air change in 4-5 hours to purge indoor pollutants and renew oxygen. 1,000 sqft. X 9' =9,000 ft^3 of space. 40 cfm of fresh air is what you need to meet ASHRAE suggestions. It could be limited to hours of occupancy. A small whole house ventilating dehumidifier like the Ultra-Aire 70H can be setup to provide 40 cfm of fresh air during occupancy. The fresh air is filtered, blended into the house air, and circulated throughout the home. Dehumidification occurs only when the indoor %RH exceeds the setting of the control. During the winter, the fresh air alone will maintain <50%RH. During the spring/summer/fall, the dehumidifier maintains <50%RH when the a/c has low/no cooling loads. The total increased cost conditioning the fresh air for the year will be less than $150.
    An erv may reduce the cost for the year by $50 for the year. This is not a good pay back. Plus the 40 cfm of fresh make-up air is benefical tos slow infiltration of unfiltered air.
    Ventilating dehu is the way to go. Check out the Ultra-Aire and the DEH3000 for a control at Ultra-Aire.com.
    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
    Jun 2007
    Location
    Minneapolis, MN
    Posts
    705
    We install ERVs exclusively here in Minneapolis. I also have one in my home and a dehumidifier in the walk-out basement.

    The ERV will better maintain the humidity level in a tight home by transferring/exchanging sensibly and latent heat. So if you are adding humidity to your home during the winter months, it will not be entirely lost to the outdoors with each exchange. An ERV will transfer a percentage of the moisture back to the fresh air stream, keeping the indoor humidity closer to the ideal 50%. This is also true in the summer cooling season and in the shoulder seasons when the only "conditioning" may be your dehumidifer in the basement.

  5. #5
    Join Date
    Oct 2011
    Location
    between here and over there
    Posts
    453
    Quote Originally Posted by BadgerBoiler MN View Post
    We install ERVs exclusively here in Minneapolis. I also have one in my home and a dehumidifier in the walk-out basement.

    The ERV will better maintain the humidity level in a tight home by transferring/exchanging sensibly and latent heat. So if you are adding humidity to your home during the winter months, it will not be entirely lost to the outdoors with each exchange. An ERV will transfer a percentage of the moisture back to the fresh air stream, keeping the indoor humidity closer to the ideal 50%. This is also true in the summer cooling season and in the shoulder seasons when the only "conditioning" may be your dehumidifer in the basement.
    Isn't it code there to install them in every home with new install? I used to live in Duluth, we had to install them in every new install. It was when I was first starting out as a installer back in 2004.

  6. #6
    Join Date
    Jun 2007
    Location
    Minneapolis, MN
    Posts
    705
    Yes. A heat exchanger must be installed for a new home, but an ERV is over and above the requisite HRV.

  7. #7
    Join Date
    Jan 2013
    Location
    Henry county,ky
    Posts
    81
    We install whole house dehumidifies, and steam humidifiers. The erv works good too, maybe look into upgrading your ail filtration system on your system. We started using IAQ air filter systems. It is expensive but they do work quite well. Just bringing in raw outdoor air isn't enough.

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