I've seen some discussion about the section G3.1.1 from ASHRAE 90.1-2007, but I still have some doubt about it.

I'm working in a project that is a build-to-suit office building with 13 floors. The second floor will be prepared to have a computer room with high intensity of process loads, a total of 347 kW is expected to be installed in this area, with 1,231 m², i.e., an equipment power density of 282 W/m².

This computer room requires specific air flow, temperature and humidity levels, with 21°C for the zone air temperature and 50% of relative humidity. In order to satisfy these conditions, a reheating system was designed for dehumidification purposes. The supply air will be cooled to 10°C, for dehumidification, and then reheated to 15.6°C, maintaining the air at the condition of 21°C to 50% in the computer room. The supply fans will maintain constant volume flows in this area, due to the high concentration of thermal loads to be dissipated. The heating coils will be supplied with hot water recovered in the chillers at the central plant.

According to Appendix G, item G3.1.1, the baseline building should have system #8 for this type and size of building. The system #8 is described with Parallel Fan Powered Boxes with electric resistance, with VAV control. But the exception “b” for item G3.1.1 states that “if the baseline HVAC system type is 5, 6, 7, or 8, use separate single-zone systems conforming with the requirements of System 3 or System 4 (depending on building heating source) for any spaces that have occupancy or process loads or schedules that differ significantly from the rest of the building. (…) Examples where this exception may be applicable include, but are not limited to, computer server rooms, natatoriums, and continually occupied security areas.”

As an exceptional condition for this computer room, can I model the baseline system for the space described above with System 4 – constant volume, packaged rooftop heat pump with electric resistance for reheating?

Can I adopt the supply air flow for the baseline with the same value considered in the proposed design, according to HVAC design documentation, maintaining the pressurization needs for that space?

Thank you in advance.