N-factor checks out
big__o
| Posted in General Questions on
I was always curious how accurate the n-factor estimates are, so i decided to measure it once i finally got the tools.
Measured ach50 was 1.48, so n-factor for zone two would be 17-20, or 0.074 – 0.087 natural ach.
I shut all windows and opened all doors, and all occupants left the building. measured co2 was 952 ppm.
After two hours the co2 was 868 ppm.
Outside co2 was 400ppm.
Plugging the numbers into the formula
https://imgur.com/a/c0cbXBU
I arrived at a natural ach of 0.0825 air changes per hour, which is an N-factor of 17.93
Right in the predicted ballpark
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Replies
That is a very interesting approach. Did you run this experiment recently? Stack effect will be greatest at the coldest time of year, so your average natural infiltration rate might be a fair amount less.
I conducted the test yesterday. Not a great difference in temperature. Outside was about 50 and inside was about 70.
I definitely plan to test it again several times in the future, especially the months where outside temperature is warmer than inside.
Per lstiburek, i assume air changes in the summer will be very close to zero but I'm excited to find out