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  1. #1
    Join Date
    Nov 2016
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    How Much Fresh Air Ventilation?!

    Hi all. First time poster! So I recently moved into a new house and itís a new build, so somewhat energy efficient. The house has 2 ac units Ė one for upstairs and one for down. For the upstairs unit there is an external mechanical damper that opens to pull in external air. They have installed the Honeywell W8150 Fresh Air Ventilation Control module to control how frequently this damper opens within a 1-hour cycle, and it seems to be very frequent! I estimate that the system fan must run for almost 30 mins of an hour to pull in external air. So up to 12 of my 24 hours in a day?! I know ASHRAE 62.2 speaks a lot to the volume of outside air needed for interior air quality, but this seems like a lot of external air to pull into the house! And I just canít wrap my head around spending money to condition the interior air, and then pull in a bucket load of unconditioned outside air that then also needs to be conditioned! I live in the south with very hot and humid summers so I canít imagine how this will work in the summer. Does anyone have any thoughts?

    In addition, is anyone familiar with the Honeywell W8150 module? If I understand it correctly, if I set this to off on the module itself I think it will simply open the mechanical damper for external air whenever the system clicks on to cool or heat the house, is that right? In which case, surely itís better to just pull in the outside air whenever the system kicks on and then itíll condition the air at the same time itís pulling it in, as opposed to currently where it seems to just pull in a load of air based on the module settings. And because itís winter now, I can actually feel the cold outside air coming through the vents for portions of the hour even though Iím trying to keep the house warm.

    Any opinions and advice are all welcome! Thanks all!

  2. #2
    Join Date
    Jun 2003
    Madison, WI/Cape Coral, FL
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    I would be surprised if you are getting over ventilated. You need a fresh air change in 4-5 hours when the home is occupied. If you want to track fresh air, measure the CO2 levels in the home and the number of occupants. Table exist that will calculate the cfm of fresh air.
    $100 gets you a CO2 meter from
    Get a CO2 meter and track your CO2 ppm during typical day.
    Report you CO2 ppm/number of occupants and we will estimated the cfm of fresh air.
    It is not that expensive to condition 100 cfm of fresh for 10 hours per day. Much healthier.
    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"

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