[Bldg-sim] Thermal Zones

Bishop, Bill wbishop at pathfinder-ea.com
Fri Nov 12 07:00:39 PST 2010


Rob,
 
Generally, I combine all the spaces served by a single VAV box into one
thermal zone for modeling purposes. The ASHRAE 90.1 User's Manual,
p.G-19 has reasonable guidance on defining "thermal blocks". Where HVAC
zones have been designed, zones can be combined into thermal blocks for
modeling purposes when all these conditions are met (paraphrasing here):
1.)     The spaces have the same load and schedule characteristics.
2.)     Exterior zones with glazing must have the same, or similar
orientation.
3.)     Zones must be served by the same HVAC system or by the same kind
of HVAC system.
 
Chances are that the zones/spaces served by a single VAV box will meet
these criteria in a properly designed HVAC system.
 
Regards,
Bill
 
William Bishop, PE, BEMP, LEED(r) AP | Pathfinder Engineers & Architects
LLP
Mechanical Engineer
 
 134 South Fitzhugh Street                 Rochester, NY 14608
T: (585) 325-6004 Ext. 114            F: (585) 325-6005
wbishop at pathfinder-ea.com           www.pathfinder-ea.com
<http://www.pathfinder-ea.com/> 
P   Sustainability - the forest AND the trees. P 
________________________________

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Rob Hudson
Sent: Friday, November 12, 2010 9:22 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Thermal Zones
 
Hypothetically speaking, if i have a proposed design of a packaged VAV
system where each VAV serves a range from 1 to 3 rooms, does my baseline
design make the rooms serves by each VAV box a thermal zone or is each
and every room its own thermal zone?

So if i have 10 VAV boxes each serving 3 rooms, is it 10 thermal zones
or 30 thermal zones?

-- 
Rob Hudson
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