What is the term for a heating system that does not use ducts?

The term for a heating system that does not use ducts is best associated with a hydronic heating system or an electric baseboard heater. These systems heat spaces without relying on air ducts, which is a characteristic of ductless heating methods.

Hydronic heating, for example, uses water as a heat-transfer medium. This system typically consists of a boiler that heats water, which then circulates through pipes to radiators or radiant floor heating, directly warming the rooms without any need for ducts. Similarly, electric baseboard heaters are installed along the baseboards of a room and provide direct heat without air circulation through ducts.

In contrast, a ductless range hood pertains to kitchen ventilation rather than heating, and a forced air system does indeed use ducts to circulate heated or cooled air throughout a home. Therefore, the most fitting definitions among those provided relate to either hydronic systems or electric baseboard heaters, both of which operate effectively without the use of ducts.