What is night setback and what energy benefit does it provide?

• A. Increasing setpoint for cooling or lowering heating setback during unoccupied hours to save energy; reduces chiller/boiler run.
• B. Decreasing all temperatures to the minimum.
• C. Increasing demand.
• D. Only affects humidity.

Answer: (A)

Night setback is about letting the building drift away from occupied comfort temperatures during unoccupied hours to save energy. For cooling, you raise the setpoint so the space warms up; for heating, you lower the heating setpoint so the space cools down. The energy benefit comes from cutting how long the HVAC system runs, which reduces the load on the chiller or boiler and lowers overall energy use. This approach also helps with peak demand and operating costs, since equipment isn’t firing as much during off-hours. Before occupants return, the system can be brought back toward the normal setpoints to restore comfort.

Other options don’t fit because night setback isn’t about decreasing all temperatures to the minimum, it doesn’t aim to increase demand, and its primary benefit is not limited to humidity—it’s about energy savings through intentional temperature drift during unoccupied times.