Variable air volume systems with outside air economizer cycles when designed for high-rise buildings are typically specified with return air fans. Besides introducing a complex control problem, return air fans are significantly energy inefficient when compared to relief fans. This paper presents the analyical results of a study conducted to determine the energy usage differences anticipated in a high rise office building served by a variable volume mechanical air system with an economizer for both a relief fan and a return fan system. The analysis was conducted in five geographic locations in order to measure the changing impact of various climates. The locations included Boston, MA; St. Louis, MO; Atlanta, GA; Houston, TX; and Jacksonville, FL.

Units: I-P