This paper presents an approach for controlling outdoor air economizer and energy recovery systems based on minimizing total energy input to the HVAC system including, chiller, pumps and fans. The method utilizes the performance characteristics of the system components along with the outdoor and indoor air conditions to determine the optimum collection of setpoints and operating conditions. The method is demonstrated for some typical systems over a range of environmental conditions using detailed simulations and representative equipment characteristics. Potential energy savings due to improved control algorithms are presented and discussed. Implications on improved design and optimization of building economizer and energy/enthalpy recovery systems are also summarized.