Model simplification & LEED

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Fellow eQuesters,

I am modeling an office building with a few HVAC zones, each of which is
supplied through a VTU. Within each zone are many walls which,
collectively, could require the rest of my life to model. To model these
walls seems a bit more detail than physics justifies, since they generally
separate rooms within zones rather than the zones, themselves, and because
all of the building is intended to maintain the typical 75 degrees F
temperature and the air will, of course, circulate among nearby rooms.
Can anyone tell me whether choosing to model only those walls that are
at the borders of HVAC zones will cause an objection by the LEED/USGBC
people who will be reviewing the building (and my model) for LEED

Lars Fetzek

Lars Fetzek's picture
Joined: 2011-09-30
Reputation: 0

Zones, Sir, should suffice. I assume you speak of interior walls.

John Aulbach's picture
Joined: 2011-09-30
Reputation: 1

Lars - zones should suffice. Appendix G lays out some guidelines for

7. Thermal Blocks - HVAC Zones Designed

Where HVAC zones are defined on HVAC design drawings, each

HVAC zone shall be modeled as a separate thermal block.

Exception: Different HVAC zones may be combined to create a

single thermal block or identical thermal blocks to which multipliers

are applied, provided that all of the following conditions are


(a) The space use classification is the same throughout the thermal


(b) All HVAC zones in the thermal block that are adjacent to glazed

exterior walls face the same orientation or their orientations vary by

less than 45 degrees.

(c) All of the zones are served by the same HVAC system or by the

same kind of HVAC system.

If you want to account for some of the mass from the interior walls, you
can define the interior mass in the "contents" tab of the space

Vikram Sami, LEED AP

Vikram Sami's picture
Joined: 2011-09-30
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