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Thread: Sizing a HRV

  1. #1
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    Sizing a HRV

    I live in northeast Wisconsin and I'm sizing an hrv for my home. I posted Honeywell sizing chart. My basement has four heat runs and a closed return register it is not a finished basment. Do I size for the living area only or should I size for the basement? Using the air changes per hour calculation I need 120 w/basement and 60cfm w/o basement. Name:  IMG_1628.jpg
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  2. #2
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    Keep in mind that your home will get the natural fresh air ventilation from the wind, the stack effect, and exhaust air needed for the clothes drier, kitchen exhaust hood. During normal winter weather, this is enough fresh air to purge indoor pollutants and renew oxygen. The ERV will not change any of the before mentioned items need for make-up air. During the mild seasons of the year, natural air infiltration declines and mechanical fresh air is needed. Most do not ventilate during mild seasons when the windows are closed.
    What make you think you need fresh air ventilation during the winter? If the windows have condensation, than yes, mechanical fresh air is need during cold weather. My guess is that 60 cfm will be plenty during cold windy weather. During mild summer weather, the need will be slightly higher. What about the make-up air for exhaust devices? Also Wi is a green grass climate that needs supplemental dehumidification to keep the home dry when the outdoor dew points are high and there are low/no sensible cooling loads. This requires 3-4 lbs. of supplemental dehumidification to maintain <50%RH throughout the basement and conditioned spaces.
    I suggest a whole ventilating dehumidifier instead of ERV. You have a couple great ones manufactured right there in WI. Ultra-Aire and Aprilaire.
    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
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    I currently use an ultra aire 90 with mechanical fresh air. According to my Netatmo my Co2 is 350-700ppm. I have fresh coming in but not exhausting out. We do have an broan ecm bath fan that I will keep running for time to time. I don't have any make up are now and that was on the to do list. The hrv was just a thought and would give me something to do for a couple hours. I really don't think I "need" one but the thought of exhausting air got my mind working.

  4. #4
    Join Date
    Jun 2003
    Location
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    Congrats! For a couple hours, no payback or benefit. CO2 low enough to indicate good indoor air quality. 700 ppm indicates 40 cfm of fresh air per occupant. Save your money.
    What is you %RH now and in the summer?
    Keep us posted. How long have had the UA 90?
    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
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    Location
    Northeast Wi
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    Summer RH is <50%. I can get the basement down to 42% and that usually keeps the rest of the house at 48%. In the winter I keep it about 45%. I have had the ultra aire about 4 years now. I was fed up with portable dehum failing about every other year. The ultra aire keeps the basement dry in the summer and now that I finally added mechanical damper we get some fresh aire. Do you have any suggestions for exhausting stale air or because the Co2 level is good is it even needed?

  6. #6
    Join Date
    Jun 2003
    Location
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    Do not worry about blowing out the windows. You have a square foot of leakage for the air to exit. How many occupants or how big is you humidifier?
    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"

  7. #7
    Join Date
    Jun 2013
    Location
    Northeast Wi
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    3 occupants, 1288sq/ft, powered April air humidifier. Windows stay dry. colder days I turn down the humidistat to prevent to much moisture.

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