[Equest-users] ASHRAE 90.1 Appendix G ventilation when fan cycling

Dahlstrom, Aaron ADahlstrom at in-posse.com
Wed Mar 7 07:06:22 PST 2012

Bill - an excellent question, one I haven't looking into too much before...

Here's a little logic, though:

1.      All LEED buildings are required to meet Section 6.4 in its entirety. (per the pre-requisite language)

2.      The ventilation rates are required to be identical between the proposed and baseline per G3.1.2.5

3.      If there is a reason why the proposed building would need ventilation during unoccupied hours, both the proposed and the baseline shall have ventilation during those hours per G3.1.2.4

I think that's enough logic to make the case for what you've proposed. Thoughts?


Aaron Dahlstrom , PE, LEED(r) AP
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From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bishop, Bill
Sent: Tuesday, March 06, 2012 5:02 PM
To: Equest-users at lists.onebuilding.org
Subject: [Equest-users] ASHRAE 90.1 Appendix G ventilation when fan cycling

I seem to recall that, when fans are cycled during unoccupied periods per G3.1.2.4, ventilation should be zero - at least in the baseline. I have done this before in eQUEST by setting a MIN-AIR-SCH to zero during unoccupied hours. I can't find any reference to this requirement in Appendix G. However, in the mandatory provisions section Shutoff Damper Controls, "Ventilation outdoor air dampers shall be capable of automatically shutting off during preoccupancy building warm-up, cool down, and setback..." (There are exceptions I'm not listing.) Is the general rule that Appendix G and/or LEED models have zero ventilation during unoccupied periods?


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