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  1. #1

    HRV Help for New Construction in Wisconsin

    My wife and I are planning on building a new house in Southeast Wisconsin (Milwaukee area.) We are strongly considering having an HRV unit installed to circulate fresh air into the tightly sealed new construction home.

    We are not particularly interested in getting a variable speed fan on the furnace. We're not the type that run the furnace fan all the time in the winter, (we disagree whether to run it all the time in the summer )

    The question is: Is it a good or bad idea to install an HRV unit with a traditional (non-variable speed, not sure what to call it) furnace? I understand that the HRV has a separate fan from the furnace (right?) and I don't quite understand what is going to happen when one is on and not the other. Are the two fans synched together? What does the HRV do when the furnace fan is completely off? What does the HRV do when the furnace fan is on but the furnace/AC is not actively heating/cooling? Do we have to remember to switch on the HRV at the thermostat or is that automated? What is the recommended usage pattern in the summer and winter?

    We would greatly appreciate any insight and/or advice from the experts on the forum.

  2. #2
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,064
    Are you sure you really need a HRV? In my youth, I sold many HRVs, in the last energy crisis. I discovered that you would seldom them during cold windy weather, because the homes got enough fresh air natural. Yet when the winds calmed and the temps moderated, the natural infiltration declined decline and ventilation was needed whenever the windows were closed and the home was occupied. So you invest big bucks in the heat recovery and do not need it when heat could be recovered.
    The next problem is that fresh air in a home during weather makes them damp. The HRV does nothing to fix the problem. I seldom recommend an ERV/HRV unless the is extremely tight and it is a long heating season with a high ventilation load.
    It makes more sense to install a whole house ventilating dehumidifier that is able to provide fresh air makeup air when the home is occupied and the winds are calm. These units blend in fresh air with the house air, filter the blend and circulated it through the home via heating/ac ducts. When the outdoor dew points are +60^F, indoor air need dehumidification to control the moisture fresh air and occupants. Basements in green grass climates need <50%RH, dew point <50^F. Keeping the home <50%RH is comfortable and eliminates mold and dust mites throughout.
    Get the Ultra-Aire whole house ventilating made in Madison. A much better value.
    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"

  3. #3
    Thanks for the reply teddy bear. I don't really understand why I would not use the HRV in cold windy weather or in moderate temps. Ideally, wouldn't the HRV just be connected to the thermostat and kick in when the furnace kicks in? Are you saying that we would have to manually turn it on separately from the furnace, or that I would want to manually disconnect it in cold weather?

    I get what you're saying about it bringing in humid air in the summer, and I see how the ultra-aire could help with that. What will that do for me in the winter? Keep in mind I'm in Wisconsin, with a long heating season and short cooling season, and this is new construction, so I expect the house to be very tight. I'm not sure what you meant by high ventilation load. The house is a ~3000 sqft 2 story plus basement. We will not be finishing the basement.

  4. #4
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,064
    Quote Originally Posted by JCIsMe View Post
    Thanks for the reply teddy bear. I don't really understand why I would not use the HRV in cold windy weather or in moderate temps. Ideally, wouldn't the HRV just be connected to the thermostat and kick in when the furnace kicks in? Are you saying that we would have to manually turn it on separately from the furnace, or that I would want to manually disconnect it in cold weather?

    I get what you're saying about it bringing in humid air in the summer, and I see how the ultra-aire could help with that. What will that do for me in the winter? Keep in mind I'm in Wisconsin, with a long heating season and short cooling season, and this is new construction, so I expect the house to be very tight. I'm not sure what you meant by high ventilation load. The house is a ~3000 sqft 2 story plus basement. We will not be finishing the basement.
    The amount of fresh air that infiltrates a home depends on the wind and inside/outside temps that cause the stack effect. Usually an air change in 4-5 hours is adequate to purge the indoor pollutants and renew oxygen. Most of our well built homes leak enough fresh air during the colder windy weather and do not need fresh air ventilation during high winter pressures. But as the wind declines and the temps moderate, the pressure declines to the point where mechanical fresh air ventilation is needed. Ventilating when you have enough fresh air, wastes energy even with a HRV. The investment in an HRV is substantial. If you do not need for the very cold weather, there is no return on the investment.
    You have a need for make-up air for your clothes drier, kitchen hood, and bathrooms. Makeup fresh air ventilation will help these device by providing air and avoiding depressurization. Invest the ventilation dollars in a whole house ventilating dehumidifier as your primary ventilation humidity control device.
    If you have plenty of cash and want it all without regard to investment, get both. It is most critical to have <50%RH and fresh air throughout the year. If you have a super tight home and high occupancy, a Hrv will save $100 in heating per year.
    Keep us posted. I also have a home in WI and have many years in the industry.
    If you must get a HRV, I suggest removing stale air from the baths and open parts of the home and returning the fresh air to the Furnace return. You need not operate the blower while HRV is operating.
    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"

  5. #5
    Again, thanks for advice TB. I wasn't aware of the dehumidifier option before so we'll definitely take it into consideration.

    Just to be clear, it is perfectly OK to use the HRV or the dehumidifier with a single or dual speed furnace instead of a variable speed furnace?

  6. #6
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,064
    Quote Originally Posted by JCIsMe View Post
    Again, thanks for advice TB. I wasn't aware of the dehumidifier option before so we'll definitely take it into consideration.

    Just to be clear, it is perfectly OK to use the HRV or the dehumidifier with a single or dual speed furnace instead of a variable speed furnace?
    Yes.
    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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