[BLDG-SIM] ASHRAE 90.1-2004 App. G, Hospital Baseline

[Dana Troy]

Hello all,
 
I am currently working on the ASHRAE 90.1-2004, Appendix G baseline model of a hospital in Oregon. The part of the building being analyzed is a 40,000 sf, 3 story addition to an already existing building of approximately 90,000 sf. I am having some issues determining what to use for the baseline HVAC system. Here are some key details of the current as-designed building:

*	Reheat fan system
*	Constant volume, 60,000 cfm
*	100% outside air
*	Draws heat from two boilers and two chiller in a central utility plant that also serves the rest of the building

These design parameters lead to some confusion when selecting the HVAC baseline systems. For example:

*	Since the addition is served by a system that serves the entire building, should building be modeled as an ~130,000 sf building? This would make it System 5 under Table G3.1.1A. Problems with this are that it calls it out to be a PVAV w/ reheat, which is not a legitimate comparison. If the baseline is supposed to be PVAV, the OSA requirements need to be the same anyways (G3.1.2.5), therefore effectively making it a constant volume system.
*	Should the sf be taken relative to only the addition (40,000 sf)? This is also not a fair comparison between the two systems because the addition draws heating and cooling from a system designed for a much larger square footage. 

I guess my main questions are if anyone has dealt with large, constant volume, 100% OSA systems and their baseline HVAC systems and if anyone has modeled additions that are served by a larger CUP.
 
Thanks for any help in advance.
 

Dana Troy, EIT
Energy Analyst 

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