[Equest-users] ASHRAE 62.1 Ventilation Rate Procedure for 100% Outside Air System with FCU

[omoltay at mimtarch.com]

Dear All,

I hope you excuse the fact that I am writing an e-mail not related to
building simulation but to outside air ventilation of a LEED candidate
building. Since there are so many people experienced with LEED here, and
since I got no success from other groups (ie. bldg-rate), I thought I
would give it a try.

We have several systems in the building that are constant volume 100%
outdoor air systems supplying ventilation air to rooms from ceiling
grills. In some of the rooms there are plenums, in others the ceiling is
open. In most of the cases, in vicinity of the outdoor air grill, ceiling
fan coil units are installed to condition the air. FCU supply is ducted,
while return is without duct.

Assuming that this is a system with only secondary recirculation, are we
still required to calculate the system ventilation efficiencies (Ev) using
Appendix A of ASHRAE 62.1? The design airflow rates have been calculated
to be 30% higher than Ventilation Rate Procedure requirements using
Vot=sum of all zones(Voz), but since the LEED submittal forces us to enter
Ev values for each zone, we're scratching our heads now on whether such a
system is after all also to be considered a multiple-zone recirculating
system.

Thank you very much,

Omer Moltay, LEED AP
Mimta