All,

A (hopefully) simple ASHRAE 90.1 baseline system question.

I have a building which is part office, part maintenance/storage garage. The garage/maintenance portion is about ? of the total GFA. Appendix G system type is #5 - Packaged VAV w RH. However, I want to apply G3.1.1c as an exception, which states that system 3 or 4 should be used for zones which have special pressurization relationships, cross contamination requirements or code-required airflow rates. This is definitely the case.

My question is do I use system 3 or 4 for the garage/maintenance zones (both the predominant condition and the zones with the special requirements) or the office zones? The wording leads me to believe its actual the office zones which need to be system type 3, but this seems backwards, and it's essentially the reverse of what is installed, which is VAV in the office, PSZ in the garage.

Regards,

Adam