For baseline HVAC system type, ASHRAE 90.1-2007 has the following
exception (G3.1.1 d.):
"For laboratory spaces with a minimum of 5000 cfm of exhaust, use system
type 5 or 7 that reduce the exhaust or makeup air volume to 50% of
design values during unoccupied periods."
Similarly, "systems serving laboratories with exhaust rates of 5000 cfm
or greater" are excepted from the baseline energy recovery requirement
(G3.1.2.10 h.).

When applying this exception, is it 5000 cfm per space? Per floor? Per
building? Per system?

Thanks,

William Bishop, PE, BEMP, LEED(r) AP