[BLDG-SIM] Oh, what a tangled web we weave...

Lynn Qualmann LQualmann at sbwConsulting.com
Mon Jul 16 10:06:34 PDT 2007


Thanks to everyone who responded to the threads that came from the
original question. With respect to the note immediately below, how is
the demand for outside air determined when DCV is modeled in eQuest? I
was assuming the inputs would be the number of occupants (and their
activity levels) and the volume of the space. If deleted plenum volumes
are re-assigned to occupied spaces, the CO2 concentration (and
presumably OA fraction) should clearly be reduced in a real-life DCV
situation. Does the eQuest model of DCV take this into account or is it
more simplified?
 
R. Lynn Qualmann, P.E.
SBW Consulting, Inc.
2820 Northup Way  #230
Bellevue, WA  98004
Phone:  (425) 827-0330
FAX:     (425) 822-8119
e-mail:  rlq at sbwconsulting.com

  _____  

From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of David S
Eldridge
Sent: Monday, July 16, 2007 8:13 AM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] Oh, what a tangled web we weave...



John, that is a good point if your program is modeling the CO2
concentration explicitly.

 

If you (or simulation program) are using the scheduled quantity of
people as the surrogate for CO2 measurements then it would be the same
amount of OA with or without plenums.

 

(How ironic is that?  Using number of people in the model as the
surrogate for CO2 measurements...which in the real building is the
surrogate for the number of people...)

 

David

 

 

From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of
Peterson, John
Sent: Friday, July 13, 2007 8:05 AM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] Oh, what a tangled web we weave...

 

The plenums subtract from the total room volume.  If the return is
ducted, this makes a large difference.  Also while the plenum & room may
have the same or nearly the same temp/humidity, ventilation rates for
the room might be calculated based on a CO2 level difference.  The CO2
calculation is based on the room volume, which relates directly with OA
needed, and hence the energy to condition that OA.  The plenum can mean
a big difference in room volume flows when extrapolated across an entire
building.  

 

John Peterson, PE, LEED AP

625 N. Washington Street     Alexandria, VA  22314 

Tel: (703) 683-9700 

Fax: (703) 683-2480 

 

 

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