# How to calculate ventilation rates from 62.1? 6 Min Solutions HVAC - Q66, Q67, Q76.



## On_Wisconsin (Mar 23, 2014)

Working through the 6M solutions right now and not following the seeming inconsistency between these three ventilation questions that reference ASHRAE 62.1.

Q66 calculates the ventilation requirement using Vbz = RpPz + RaAz while Q67 and Q76 use only the occupant density (RpPz) to calculate the required airflow rate.

Do you only add the area outdoor rate when you aren't given the # of people and need to calc it based on density? Thanks.


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## On_Wisconsin (Mar 23, 2014)

Nevermind - I didn't understand how the "default values" column worked. Bad first post!


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## shixiangnan1002 (Mar 30, 2014)

Q66 uses 15 cfm/person. Q67 uses 20 cfm/person. Does anyone know where those numbers come from? I have a 62.1-2010 but couldn't find those numbers, at least not in the table 6-1


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## kalvinjk (Mar 31, 2014)

It depends on space type. Look under the default values column and directly under combined outdoor air rate.

Normally the range is 15-20 cfm for most spaces (office, classroom, etc).


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