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  1. #1
    Join Date
    Aug 2015
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    Air Quality Test Results - Now What?

    Good Morning,

    I have a 3-ton two-stage 24ACB7 w/ NIM Control 16 SEER, Furnance 59MN7A100VZ1 97.3% AFUE, and AA600M humidifier w/ Infiniti controller. We currently use a Nordic Pure MERV 12 filter that we replace every ~6 months.

    We recently had a air quality test conducted. The following areas of the test reflected 'action needed':

    1 - Particles - 56.8 ug/m3 - The EPA states <50 is good and 51 to 100 as moderately good so I suspect no immediate mitigation is necessary.

    2 - CO2 - 805 ppm - ASHRAE guidance is difficult to interpret, but it seems this level is reasonable and doesn't require immediate mitigation.

    For #1, recommendation is clean ducts, add air filtration system, install UV light in cooling coil to prevent mold. Would would be the most effective mitigation and, if you were me, would you take any action. To my knowledge, no one in my home has any health issues. I suspect the high particle number is due to my dog and three children that are in and out constantly.

    For #2, recommendation is to install an ERV/HVR. Seems overkill based on above.

    Thoughts and feedback welcome.

  2. #2
    Join Date
    Dec 2015
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    I agree with your conclusions. My only suggestion, for a complete IAQ assement, is to measure VOC levels with either Gas chromatography or PID meter. Both particulates and CO2 can be acceptable while VOC levels are high.

  3. #3
    Join Date
    Mar 2013
    Billington Heights, NY
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    ASHRAE says 1000 ppm inside is "OK". For comparison, outdoor air has recently hit 420 ppm. The official number seems rather high, to me.

  4. #4
    Join Date
    Jun 2003
    Madison, WI/Cape Coral, FL
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    Checking fresh air change rates does not tell the complete story. When the wind blows and/or the home is warm compared to outside, high stack effect, you get much more fresh air infiltration. During calm winds and moderate temperatures, the natural air change declines to near nothing.
    Most suggest a fresh air change in 4-5 hours when occupied.
    CO2 levels indicate the amount of fresh air per occupant. With 450 ppm of CO2 in outside air, 800 ppm CO2 indicates 30 cfm of fresh air per occupant.
    The volume of 2,000 sq.ft. with 9 ft. ceilings is 18,000 sq.ft. If you had 5 occupants in 18,000 sq.ft. of well mixed space at 800 ppm would suggest 150 cfm of fresh air change. This would be an air change in 120 mins. or 2 hours, plenty of fresh air. This would be typical of a cold windy day in leaky home.
    Yet this home on warm, calm day/evening with the windows and doors closed, may be 2,000 ppm CO2, which is 9 cfm of fresh per person. This is a fresh air change in 7 hours. We would like a fresh air change 4-5 hours to purge indoor pollutants and renew oxygen.
    Most well built modern home should have minimum of a simple make-up air system that brings fresh air when the home is occupied. You have exhaust device like the kitchen hood, bath fans, clothes drier than need make-up air to function. An HRV/ERV do not provide make-up air for exhaust devices.

    Also consider that the moisture content in the outside fresh air air varies from being very dry to almost 100%RH. You are most comfortable healthy at 40-60%RH. With 5 occupants in a 2,000 sq.ft. home, you may need to add moisture during the coldest windy weather. The same home with 80 cfm of fresh make-up air during the mild months of the year when the moisture content of outside air is high plus the moisture from the occupants will be damp.
    You are dependent on the a/c operating enough to remove the +6 lbs. of moisture in the air to maintain <50%RH. A small whole house dehumidifier would ideal for maintaining <50%RH during the wet cool times of the year.
    Monitoring the temp/%RH/CO2 levels in the home throughout the year to confirm how well your home is preforming.
    Most homes in green grass climate need supplemental dehumidification and fresh air ventilation. If the winters are cold and windy, a humidifier may also needed. For extremes, also consider an ERV/HRV.
    HOpe this helps.
    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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