A VAV box with hot water reheat is a type of HVAC system that works to provide temperature control for a space. It is typically used to control the temperature in large commercial buildings, such as offices and schools. The system is made up of an air handler, a fan, and a hot water coil. The hot water coil is used to deliver heated air to the space, while the fan circulates the air. The VAV box is used to regulate the air flow and can be set to maintain a certain temperature. It works by regulating the amount of air entering the space, as well as the temperature of the hot water passing through the hot water coil. The system can also be used to supplement a boiler, allowing the boiler to operate more efficiently and reduce energy costs. With the VAV box, a building can maintain a comfortable temperature in cold weather while also helping to reduce energy costs.