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OSA and ASHRAE codes for such

OSA and ASHRAE codes for such

OSA and ASHRAE codes for such

(OP)
If I have net rentable area of the office building and total cfm of fresh air fans how would I determine air changes? The building has 369k and the total cfm of osa intake and exhaust is 12k.  Additionally I have an 8' x 12' louvre that supplies unconditioned fresh air x 2.

RE: OSA and ASHRAE codes for such

12k cfm OA is good for 600 occupants. Typical occupancy of a 369,000 ft2 office building might be 2,500-3,000.

ACH = cfm * 60 / volume

If you have 9 ft ceilings for example:

ACH OA = (12000 * 60)/(369000 * 9)
ACH OA = 0.22

Pretty low OA for this big a building. If you supply one cfm/ft2 (typ.) you're talking AHUs at about 3% outdoor air. Typ. office AHU usually around 10-20% minimum OA range.
 

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