Exception c from G3.1.1 of ASHRAE 90.1-2004 indicates we should use separate single zone systems conforming with the requirements of System 3 or System 4 in our baseline energy model for any zones having special pressurization requirements. We assume this would include various laboratory and hospital spaces, among others. Can these baseline systems be modeled as constant volume reheat systems? In a humid climate, Systems 3 and 4 would not be suitable for a laboratory with 100% or high outside air percentages unless reheat was allowed. Exception c to section 6.5.2.1 allows simultaneous heating and cooling where there are special pressurization relationships, but the Performance Rating Method of ASHRAE 90.1-2004 does not seem to reference using prescriptive requirements to determine how our baseline model can be set up.
The applicant is requesting an exception to the baseline system modeling as per ASHRAE 90.1-2004 Appendix G Performance Rating Method (PRM). The PRM is not set-up for compliance purposes. It requires you to compare the building design to another building that would typically be built for the size and function of the project. Appendix G must be looked at in its entirety, not in isolation. Therefore, to maintain the integrity of the modeling protocol set forth therein, the system types cannot be switched or manipulated. Applicable Internationally.