[BLDG-SIM] Baseline HVAC Type

[Bill Talbert]

Can anyone provide feedback on the intent of ASHRAE 90.1 Appendix G
Exceptions to G3.1.1 which allow changes to the baseline HVAC systems
prescribed in Tables G3.1.1A and G3.1.1B for spaces with special
pressurization requirements or spaces where peak thermal loads differ by
more than 10 Btu/h-sqft? This exception would appear to allow Packaged
Single Zone air conditioners with gas-fired heating as baseline systems
in laboratory spaces with high equipment loads and/or pressurization
requirements. In a large lab building where the baseline system per
Table G3.1.1A is a VAV system, this could make a big difference in
calculated energy savings. A recent CIR (February  '07) on the USGBC
site implies that the exception should not be used although the question
involves reheat issues as well. It seems that a PSZ system could be
modeled successfully to meet zone conditions without reheat but does
this approach (simulating the baseline for a large laboratory building
with multiple PSZ systems) meet the intent of the exception?  Has anyone
else had any experience with this or can the A90.1 and LEED folks offer
some perspective?
Thanks,
 
 
 
 
 
 
Bill Talbert, PE, LEED® AP
Mechanical Systems
Phone: (608) 441-6677
E-mail: btalbert at aeieng.com 

Affiliated Engineers Inc.
5802 Research Park Blvd.
Madison, WI. 53719
Tel. (608) 238-2616
Fax. (608) 238-2614


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