[Equest-users] EPACT 179d ventilation reiqurements

Steve Jacobs sjacobseng at gmail.com
Mon Oct 22 10:35:10 PDT 2012

Hi everyone,
I have a question about the ventilation requirements for 179d modeling. The
NREL guidelines state to use 62-1999 for the baseline and the actual rates
for the proposed building. I'm so use to modeling ventilating rates the
same in both models I wanted to make sure I'm interpreting this correctly.
I've been doing separate 62 calculations per ASHRAE 62-1999 for the
baseline. This can make a significant difference in the OA rates between
the baseline and proposed. The 1999 rates are higher than the 2004/2007
rates for some building area types. Also, if the baseline model is a VAV
system with a critical zone driving the OA rate, the difference can be even

How have you guys handled this situation?

On a separate note, has anyone done epact for building on a central plant.
Obviously it is not covered by the NREL guidelines, so it seems like it is
on the engineer to come up with a reasonable interpretation.

- Steve
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