[Bldg-rate] Baseline System Selection for Energy Modeling for LEED EAc1

Cara Martin CMartin at novusengineering.com
Mon Aug 2 07:08:34 PDT 2010


I am curious of others' experiences with the USGBC/GBCI in terms of
modeling review of the baseline system selection for EAc1 under LEED
2009 (v3) using ASHRAE 90.1-2007, Appendix G.  I am currently modeling a
roughly 25,000 square foot, 2-story building to be used for light
commercial and retail space.  The building is pursuing Core & Shell
certification and will house multiple tenants.  The HVAC system for the
proposed building will be packaged roof top units with natural gas-fired
furnaces and DX cooling.  


As per Appendix G, the HVAC system for the baseline building is
determined by size and number of stories as follows:


1.       Nonresidential and 3 floors or less and < 25,000 s.f. = System
3 (packaged RTU, constant volume, DX cooling, fossil fuel furnace)

2.       Nonresidential and 4-5 floors and < 25,000 s.f. OR 5 floors or
less and 25,000 - 15,000 s.f. = System 5 (packaged VAV with reheat)


My building is 2-stories and just barely over 25,000 s.f. (maybe 25,800
s.f. tops).  I would much prefer to model the baseline as System 3 as
this would more closely resemble the proposed building and provide a
more realistic means of comparison.  Under Table G3.1.1A, it states that
"where attributes make a building eligible for more than one baseline
system type, use the predominant condition to determine the system type
for the entire building."  How is the predominant condition determined?
Can I claim that the height of the building (2 stories) is more
important than the square footage?  Or will the USGBC/GBCI require that
I use System 5 as the baseline because I'm even one square foot over the
25,000 threshold?  


Any input from others in a similar predicament would be most


Thank you,


Cara Martin, LEED AP BD+C

Novus Engineering, P.C.

25 Delaware Ave.

Delmar, New York 12054


518.439-8592 (fax)

CMartin at novusengineering.com


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