Design a ventilation system, in a college campus, that serves two lecture classrooms, one teacher officeand one computer lab. It is a VAV system with multiple zones, and the AHU will re-circulate a part of return air and set at minimum outdoor air (except in economizer mode). Floor supply diffusers were selected for cooling the spaces with ceiling return grills. It is displacement ventilation with low supply velocity. All rooms are internal zones (no external walls or windows) Heating will not be needed. The teachers and students are moving around the campus with a total number of 200.