Our project is a 41,000 sqft museum building with exhibit, studio, classroom, retail, office space, and an auditorium. Because of the tight humidity control, the museum requires a constant volume air handling system for the museum spaces in the building. The constant volume system designed is permissible under the ASHRAE 90.1-1999 Chapter 6 prescriptive path. Specifically, two critical requirements of the prescriptive path are satisfied by the design: - The design\'s fan power limits are within those prescribed in section 6.3.3.1 for constant volume systems. - Reheating of the supply air is allowed per exception 6.3.2.3, as this is a museum building with a specific dehumidification system. According to the ECB method, systems with water cooled condensers and fossil fuel heating that serve multi-zone non-residential spaces shall be compared to "System 2." System 2 is a VAV system with chilled water and a fossil fuel boiler. Because the space-use dictates a constant volume system, and given that the proposed system is allowable per the Chapter 6 prescriptive path, we are asking the USGBC to allow us to compare the constant volume systems of the proposed design to constant volume systems in the budget building.