Hi,

You can size systems based on ACH when you describe your system. Go to the
"Zone Components" tab then down to "Terminal Units". If each zone requires
a different ACH, uncheck the box that says "All zones are the same". Beside
Minimum Airflow you'll see a dropdown menu, the default it "cfm/person",
change that to "ACH" and you can enter your required ACH for that zone. You
can then use the arrows move onto each zone and adjust as required.

Aaron

Aaron Smith, P.Eng

M&R Engineering