Originally Posted by
garya505
On a mild Saturday afternoon and with little wind and everyone home I had 1280PPM. It stayed above 1200 well into the evening.
Here is a dilution table assuming 450 PPM CO2 outside air, good mixing of the inside air, CO2 from the occupants, and the fresh air infiltrating the space.
550 ppm = 106 cfm of fresh air per occupant in space
650 ppm = 53 cfm
750 ppm = 35 cfm
850 ppm = 26 cfm
950 ppm = 21 cfm
1050 ppm = 18 cfm
1150 ppm = 15 cfm
1250 ppm = 13 cfm
If you have two occupants at 1200 ppm CO2 inside and 450 ppm outside and with good mixing, I would estimate 26 cfm of fresh air infiltration. With a 2,000 sqft. home/ 9 ft ceilings, you should have 60 cfm as minimal adequate infiltration. If we are going to use the CO2 levels as a signal to activate fresh air because of single occupancy and a lack of natural fresh air, activate fresh air at 650 PPm.
Wait for the CO2 level to stabilize. With poor mixing, expect higher levels when the occupants are near the meter. Cold windy weather forces more fresh into the home. Calm moderate temps decrease the air change rate.
The objective is to get an fresh air change of the air in the home in 4-5 hours to purge indoor pollutants. Exhaust or makeup air ventilation decreases natural air change at 50% rate. An example is a home getting 30 cfm of natural, activating a 50 cfm exhaust fan will increase the infiltration from 30 cfm to 58 cfm. The exhaust is 50 cfm and the exfiltration is reduced from 30 cfm to 8 fcm.
Balanced flow ventilation, like an ERV, adds directly to the natural air change rate.
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"