Hybrid furnaces switch from wood to their secondary heat source automatically. If the furnace runs out of wood, a second thermostat controlling the optional electric, oil or gas components will engage and keep your house warm even if you are not at home. During power failures, the wood burning portion uses gravity air flow for emergency heating. Built with smart designs and high-quality materials, Lennox furnaces offer years of trouble-free operation and perfect comfort. Available in variety of types, from a variable-capacity gas furnace to a two-stage gas furnace, and a variety of oil furnaces, Lennox offers a range of options to meet everyone’s heating needs.