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  1. #1

    Confused HRV and humidity control

    Hello-

    I live in Wisconsin where the temp is cold for most of the year and very humid in summer. My home is 4 years old and I had an HRV installed after the first year because of the excessive moisture, ice, and frost on my windows. Even frost coming through the outside walls! The current temp outside at night is around 10F. My humidistat is set at about 50, I understand this needs to be lower the colder it is. In the morning, I have about 3 inches of condensation on one of the rooms in my house. The other rooms have about 1 inch condensation. When I set the humidistat below 50, it runs constantly for weeks, even months! Is this normal for it to run so long on a continual basis? Additionally, I have 2 fireplaces in my home which dry it out nicely during the day or at night, but then in the morning, the condensation has returned. There are 2 vents for the HRV in my living room, I believe 1 is intake (takes the indoor air out) and the other is exhaust (blows the fresh air in). Do I need more vents to remove the humidity better out of my home? We will only take 2 showers in our home per day and the fan in the bathroom runs for a good 30 minutes. I just don't know how to reduce this humidity without running the HRV constantly for months without it shutting off? Is this normal after 3 years in a new home?
    Thank you

  2. #2
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    Have you cleaned its filter recently.

    If it runs for months. Then your humidity is high, and you need the fresh air.
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  3. #3
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    This topic is, well topical. There is another thread talking about this subject.

    I will let others hash out the condensation humidty issues.

    But, as far as running it often, or for extended periods - I wouldn't worry about it too much - they're designed to run, not cycle like heating or cooling equipment.

    In other words, if the fresh air is needed, it's needed.

    Ok, I will get into the humidity discussion a little. I am of the opinion that HRV's aren't the best tool for dehumidification all the time. If ambient moisture content is higher than the indoor set-point (happens often during the swing seasons, where you are heating but temps aren't that cold), guess what, the HRV will increase (slowly) RH, not decrease it.

    Some will bring up how an HRV can combat building pressure issues, I guess as it relates to the stack effect within a building (heat rising), which can effect condensation location...

  4. #4
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    Quote Originally Posted by larobj63 View Post

    Some will bring up how an HRV can combat building pressure issues, I guess as it relates to the stack effect within a building (heat rising), which can effect condensation location...
    I thought that was whole house dehumidifiers that did that.
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  5. #5
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    Quote Originally Posted by beenthere View Post
    I thought that was whole house dehumidifiers that did that.
    Right - it wasn't my position...

  6. #6
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    Even though your house is 4 yrs old it is probably still drying out some which is directly related to some of your RH problems. Another is you may have some cold air leaking into your home. Is your home a 2 story or a ranch type home ? If you have a 2 story and the condensation is only on the 2nd floor then it could possibly be too much positive pressure in the home, or you just have way too much RH in your home and the humidifier is set too high. Does the HRV have a humidistat built in ? If not you may want to have one put in to regulate the intake of Fresh air.

  7. #7
    My home is a ranch style with a walk-out basement. The basement has had some moisture problems too, but not related to condensation on the windows. We have many windows in the basement. We had some molding on some of our items stored down there. As for your humidifier questions, we do not have a humidifier installed, there was no need for one. We do have a humidistat on the main level installed. Is is possible to bring in the more humid air when the HRV is on? For example, like the other post mentioned, between seasons the humidity outside is high approx 90%, but the temp is approx 30 F. Is is best to leave the HRV off until the humidity % outside is lowered?

  8. #8
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    Quote Originally Posted by ableibau View Post
    For example, like the other post mentioned, between seasons the humidity outside is high approx 90%, but the temp is approx 30 F. Is is best to leave the HRV off until the humidity % outside is lowered?
    If moisture is an issue, then probably, yes.

    Remember however, that colder air cannot hold as much moisture as warmer air. My point is, RH is somewhat decieving in this context.

    But yeah, that was my original point - if the outdoor air has a higher moisture content than your RH "target" inside, AN HRV will hinder, not help. AN ERV will be better off (provided the indoor moisture content is actually lower than outdoor to begin with), but the net effect will still be a rise of indoor RH, just less so with an ERV...

  9. #9
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    If you bring in 30°F 90% RH outdoor air and heat it to 70°F, you now have 20%RH.
    So using the HRV at those outdoor conditions won't raise your indoor RH.
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  10. #10

    OK

    YOU MIGHT LOOK INTO SOMETHING OTHER THAN THE HRV...APRIL AIRE HAS A FABULOUS WHOLE HOME DEHIMIDIFICATION SYSTEM, WHICH WILL ARGUABLY REMOVE OVER 90 PINTS OF WATER FROM YOUR HOME PER DAY...THIS IS IN ADDITION TO THE AGV. 25 PINTS YOUR CENTRAL A.C. WILL DO IN THE SUMMER...
    HERE IN FLORIDA WE HAVE BAD HUMIDITY ISSUES...THE HRV / ERV SYSTEMS ARE NOT REALLY THE BEST FOR DEHUMIDIFICATION...THE APRIL AIRE IS A BIT COSTLY, SO YOU MIGHT REALLY WANT TO SHOP OTHER MANUFACTURERES: HONEYWELL, ET.AL.
    Last edited by sick_puppy; 11-23-2008 at 06:05 AM. Reason: TYPO

  11. #11
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    Turn off the cap locks.
    You don't need to yell.
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  12. #12
    Thank you all for your help. I will just let it run as you stated. The house has been nice and dry the last few days - starting to get shocks. The humidistat is set at about 43%. I will see what happens in the next few days as it gets colder.

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