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Thread: Hrv yes or no

  1. #1
    Join Date
    Jul 2013
    Posts
    7

    Hrv yes or no

    I am thinking about adding hrvs to the home I am working on. The house has 3 levels basement, main, 2nd floor. The whole home has hydronic heat zoned. forced air heat pumps on the main and 2nd floor my basement has mr slim ductless splits in the basements. The home has 2 inches of foam on all external walls and the lids of the Sheetrock are foamed. The home will see long winters with lows down to -30 to as low as -50. I understand the home needs air because it's air tight. Any recommendations on an hrv brand or are they all the same. Do I need to run a separate controller or can I use one stat to control my fan coil and hrv?

  2. #2
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,366
    Quote Originally Posted by adamfrye View Post
    I am thinking about adding hrvs to the home I am working on. The house has 3 levels basement, main, 2nd floor. The whole home has hydronic heat zoned. forced air heat pumps on the main and 2nd floor my basement has mr slim ductless splits in the basements. The home has 2 inches of foam on all external walls and the lids of the Sheetrock are foamed. The home will see long winters with lows down to -30 to as low as -50. I understand the home needs air because it's air tight. Any recommendations on an hrv brand or are they all the same. Do I need to run a separate controller or can I use one stat to control my fan coil and hrv?
    During cold windy weather, even air tights homes breathe enough to not need fresh air ventilation. During calm moderate weather, even leaky homes need mechanical fresh air. The sure sign of enough fresh air during cold windy weather is dryness of the air in the home.
    How dry is the home during winter weather? If the does not need continuous ventilation during cold weather, a HRV may not be the right piece of equipment.
    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
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,190
    Without a blower door test to MEASURE Infiltration, and how effective your insulation job is, you can only Guess
    My engineer Son has a 9x11 poster that says " Without the DATA you are just someone with an OPINION"

    With your HP/ Hydronic system design, is there a hot water coil from your boiler for stage 2 heating? Seems you would not need the baseboard until it gets really cold (stage 3)
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  4. #4
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,366
    Quote Originally Posted by genduct View Post
    Without a blower door test to MEASURE Infiltration, and how effective your insulation job is, you can only Guess
    My engineer Son has a 9x11 poster that says " Without the DATA you are just someone with an OPINION"

    3)
    As others have pointed out, blower door testing measures the air leakage area in a home only. If the leakage area is on single location or plane, the leakage rate will be much reduced. An example is a single open window, which would allow wind driven air in or out or nothing depending on the direction of the wind. Four open small windows on all sides of the home would provide predictable air change. This applies to stack effect also.
    Using outside moisture content verses side moisture content considering the number of occupants is better measure of actual air leakage or air change rates. An example is 4 occupants adding 2 lbs. of moisture per hour (14,000 grains) during cold windy weather to 2,500 sqft. home. When the outdoor dew point is 20^F and indoor dew point is 47^F, there is 100 cfm of outside air passing through the home. The inside of the home will be 46%RH at 68^F (47^F dew point). 100 cfm is an air change in 4 hours. This moisture level at this outdoor moisture level is ideal. Colder temps or more wind makes the home drier/wetter. During calm weather and/or moderate temperatures air flow declines dramatically.
    CO2 buildup inside the home is similar to calculate the air change rate in the home.
    Typically homes naturally leak less than the blower door test indicate. Operating ventilation equipment during cold weather over dries most homes. Yet during mild seasons, ventilation is important. Heat recovery equipment not operating during winter or operating during mild weather has no back.

    If the home has sweaty windows at winter temps, fresh air ventilation during and heating fuel is costly, the HRV/ERV is a true energy saving device.
    Important ventilation during mild weather with dew points +60^F requires 1-5 lbs. of dehumidification to maintain <50%RH throughout the home. With all of this, consider a whole house ventilating dehumidifier as an important part of ventilation strategy in all green grass climates.
    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"

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