système de chauffage à circulation par gravité

CONT: Many older warm air systems employ central combustion but do not use a fan to circulate heated air to the living areas. These are commonly known as gravity or convection systems. To ease the flow of heated air between the living spaces and the furnace, ducts of large diameter are used. Additionally, each warm air supply duct is usually connected directly to the plenum or air reservoir attached to the top of the furnace itself.