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Thread: HRV or no HRV

  1. #1
    Join Date
    Feb 2007
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    Talking HRV or no HRV

    Hello everyone,great site.My question is concerns a HRV.I live in what can be considered a century house with add ons.I've replaced all windows and doors with good replacements and added insulation,vapor barrier etc where ever I can.Even after doing all this the house still isn't very air tight better then before but still not tight.I've decided to turf my old mid eff gas fired forced air furnace for a high eff model from Arcoaire.It seems I have two questions first off input on Arcoaire furnaces good or bad.Next my contractor wants to install an HRV unit with it,I do understand what their purpose is and how they do it but does it make sense to poke another hole in an already fairly draughty house?In my opinion there is already enough fresh outside air entering the house.One other thing the new furnace will draw it's combustion air from outside the house.Lol,one other thing the same fella tells me I woun't need a humidifier with the HRV unit?Thanks for any input.

  2. #2
    Join Date
    Aug 2007
    Location
    MN
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    2,677
    if you need a humidifier you probably don't need a hrv/erv. the hrv/erv will pull excess moisture out and dry out the home, ie. solves condensing window problems, ect. I have both, if its too dry humidifier runs, if I put too much humidity in erv takes it out. But then my house is only 7 yrs old, so fairly tight. if you have moisture problems, radon concerns, any IAQ issues then by all means get the ventilator, but I would still install a humidifier if you need one now, you will use it either way you go, I think if you use the Honeywell IAQ t-stat, they will work together and not fight against each other.
    You can't fix stupid

  3. #3
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    Quote Originally Posted by Carzie View Post
    Even after doing all this the house still isn't very air tight better then before but still not tight.I've decided to turf my old mid eff gas fired forced air furnace for a high eff model from Arcoaire.It seems I have two questions first off input on Arcoaire furnaces good or bad.Next my contractor wants to install an HRV unit with it,I do understand what their purpose is and how they do it but does it make sense to poke another hole in an already fairly draughty house?In my opinion there is already enough fresh outside air entering the house.One other thing the new furnace will draw it's combustion air from outside the house.Lol,one other thing the same fella tells me I woun't need a humidifier with the HRV unit?Thanks for any input.
    Your needing a humidifier rests with your indoor &#37;RH in your occupied home. Drier is healther but a little moisture is more comfortable. Moisture comes from the materials in your home, your basement's contact with the earth, the occupants of the home, and activities. That moisture is added to the dry air moving through the home. The volume of air varies with outdoor/inside temperature differential (stack effect), wind, and the remaining impertections. Mechanical devices like clothes drier, bath fans, and kitchen exhaust also pay a role. In addtion to removing moisture, fresh air also purges indoor pollutants and renews oxygen. If your home is a little dry in the winter, stop operating bath fans(showering) and kitchen exhaust (boiling water). Your bigger problem is fresh air when the home is closed-up during spring/summer a/c/fall. Without winter stack effect even leaky homes do not have enough fresh air to purge pollutants and renew oxygen. Experts recommend 75-100 of fresh air any time a home is occupied. This is about the same amount of air required to remove winter moisture. Here is the non-winter problem. In green grass climates, outdoor moisture levels are high enough that adequate fresh air makes a home damp enough to grow dust mites everywhere and mold on the cooler surfaces. So the signs of adequate fresh air are the home is dry enough in the winter but wet in "grass growing" times of the year. When a properly tuned a/c has a high cooling load, enough moisture is removed to maintain <50%RH. During wet cool weather (low/no cooling) with 75 cfm of fresh air, the home will be damp enough to develope problems. Originally, I felt HRV/ERVs were the solution to the tight a/ced home. After recognizing this suttle summer humidity problem 17 years ago, I have been making a argument for minimum fresh air to home when occupied, while maintaining <50%RH during the wet time of the year. There are several ways, but the simplest method is a whole house ventilating dehumidifier. The ventilating dehu is the ideal equipment to provide fresh air when occupied and maintain <50%RH regardless of the season. Inovative A/C contractors recognize the need and maket some part or all of this. Your contractor is part of the way-HRV for fresh air when you need it least. Most contractors do not realize the lack of fresh air and moisture problem during rest of the year. Fresh air and controlled humidity is important for health and comfort. Season greetings, TB
    Last edited by teddy bear; 11-28-2007 at 12:02 PM. Reason: spelling
    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
    Feb 2007
    Posts
    19
    During the colder months my current humidifier can only manage to bring %Rh up to about 25%.As for exhaust fans I don't run them in the winter and my hood fan doesn't vent outside.Thanks for your input everyone.

  5. #5
    Join Date
    Aug 2007
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    MN
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    Quote Originally Posted by Carzie View Post
    During the colder months my current humidifier can only manage to bring %Rh up to about 25%.As for exhaust fans I don't run them in the winter and my hood fan doesn't vent outside.Thanks for your input everyone.
    then you don't need a HRV, sounds like th house has plenty of infiltration, maybe have an energy audit done, blower door test, something to help tighten up the house a bit, before resorting to a bigger humidifier.
    You can't fix stupid

  6. #6
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    Quote Originally Posted by Carzie View Post
    During the colder months my current humidifier can only manage to bring %Rh up to about 25%.As for exhaust fans I don't run them in the winter and my hood fan doesn't vent outside.Thanks for your input everyone.
    Measuring %RH on the high or low end of the scale is difficult for most meters. 40%-75% RH is within most meter's range. To check your %RH meter, conside that crushed ice in water (32^F) in a metal bowl will condensate in room air at 68^F, +26%RH or at 72^F, +23%RH. In other words, if you do not get condensate on a metal bowl with crush ice/water, the dew point of the air is less than 32^F or temps/%RHs stated. To avoid consensation on windows and outer skins of walls during extreme cold weather (<10^F outside), your dew point should be in this range. You may add 1% RH for each degree of outdoor temperature increase. Season Greetings. 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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