The selection of an HVAC control system depends on the building’s size, complexity, and occupancy patterns. For small to medium-sized buildings, a simple pneumatic or electric control system may be sufficient. Larger, more complex buildings may require a direct digital control (DDC) system, which can integrate with building automation systems (BAS) and provide advanced features like scheduling, trending, and alarms. It’s essential to consider factors such as system scalability, user interface, and compatibility with existing equipment when selecting an HVAC control system.