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<DIV>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?</DIV>
<DIV>Thanks,</DIV>
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<DIV><FONT face=Technic>Bill Talbert, PE, <SPAN style="FONT-SIZE: 12pt; LAYOUT-GRID-MODE: line; FONT-FAMILY: Arial; mso-bidi-font-size: 10.0pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA"><SPAN style="FONT-SIZE: 12pt; LAYOUT-GRID-MODE: line; FONT-FAMILY: Technic; mso-bidi-font-size: 10.0pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA; mso-bidi-font-family: Arial"><FONT size=2>LEED® AP</FONT></SPAN></SPAN><BR>Mechanical Systems</FONT></DIV>
<DIV><FONT face=Technic>Phone: (608) 441-6677<BR>E-mail: btalbert@aeieng.com<BR><BR>Affiliated Engineers Inc.<BR>5802 Research Park Blvd.<BR>Madison, WI. 53719<BR>Tel. (608) 238-2616<BR>Fax. (608) 238-2614</FONT></DIV></BODY></HTML>