[BLDG-SIM] AHSRAE 90.1, Appendix G Question

[Paul Riemer]

Hi Mark,
"Source" is a peculiar word there in G3.1.2.10.f. but I would tend to
interpret it more as an exhaust fan system rather than a diffuser, hood,
or snorkel.  

The User's Manual does not address the Appendix G section but it does
expound on the prescriptive compliance path's  matching exception in
6.5.6.1h:

"Where the largest single exhaust source is less than 75% of the design
outdoor airflow. This exception is provided to account for the
impracticality of recovering heat from multiple exhaust sources for a
single outdoor air intake. An
example could be a high-rise residential facility with a single
pressurized outdoor airshaft but a half-dozen toilet and kitchen exhaust
risers."

Although that is a bit unsatisfying because its specific example refers
to a multiple "risers", I think it still helps.

I would ask yourself: Is there a single physical location in the current
design with an exhaust volume that is at least 75% of the design outside
air flow?

Hope that helps.

Paul Riemer
The Weidt Group




-----Original Message-----
From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of Mark
Prince
Sent: Monday, August 20, 2007 4:19 PM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] AHSRAE 90.1, Appendix G Question

I have a question about ASHRAE 90.1-2004, Appendix G.

I'm performing an energy model of a building that has a animal holding
(vivarium) facility within it.  The vivarium is served by its own air
handling unit, and the unit is 100% outside air.  Now, our proposed
design is not going to have any exhaust air energy recovery for this
vivarium air handling unit.

Based on Appendix G, I don't think I need to model the baseline building
with any heat recovery based on exception G3.1.2.10.f.  Am I correct in
assuming this?  This exception seems odd to me. Because my vivarium area
has a lot of exhaust sources (many exhaust diffusers) it would appear
that almost all 100% outside air units would meet this criteria.

In addition, I cannot utilize Exception G3.1.2.10.b to remove the energy
recovery from my vivarium air handling units.  Vivarium exhaust is not
considered toxic.

Does anyone disagree with my reasoning?

Thanks,

Mark Prince
Affiliated Engineers
5802 Research Park Blvd.
Madison, WI 53719
(608) 441-6668
mprince at aeieng.com


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