What type of HVAC system utilizes water for heat transfer?

The correct choice is hydronic systems, as these HVAC systems specifically use water as the medium for heat transfer. Hydronic systems function by circulating hot water through pipes to radiators, underfloor heating systems, or fan coils, where it releases heat to warm the surrounding air or surfaces. This method is highly efficient for heating spaces and can also provide cooling in some configurations by using chilled water.

Other types of HVAC systems, such as split systems and air-based systems, typically rely on air as the heat transfer medium rather than water. Additionally, refrigerant systems are designed to use refrigerants that absorb and release heat through phase changes, not water. Understanding the distinct characteristics of these systems highlights the unique role that hydronic systems play in effective climate control by utilizing water.