Hydronic heating is more energy efficient than forced-air heating, since the hot water inside the sealed hydronic system takes longer to lose heat once it reaches temperature. Heated air cools rapidly as it flows through a ventilation system, requiring the system to work harder to warm the home.
A hydronic system is a closed loop filled with water, antifreeze or another thermal liquid. A boiler heats this water before forcing it through a series of pipes. These pipes may be underfloor and in-wall heating units, or the liquid may flow to radiators or baseboard heaters situated in each room. There, the liquid radiates heat into the room before flowing back to the boiler to be reheated.
The chief disadvantage of a hydronic system is that it takes some time to reach operating temperature. The boiler must heat the water, and the water must radiate heat through the pipes or baseboard heaters into the room. However, once the system reaches its peak temperature, it takes less energy to hold it there due to the slow heat loss experienced by the liquid. In some cases, the hydronic heating system may also provide hot water for the home, replacing an energy-hungry appliance for further efficiency gains.