How do furnace heating systems typically work? ignition of fuel creates a pressure change inside the furnace, causing a piston to exhaust hot air into the building. a bimetallic strip absorbs thermal energy from the air outside of the building, causing the transfer of thermal energy from fuel to the air inside the building. energy in the fuel’s chemical bonds is converted to thermal energy, which is then transferred to the air inside the building. thermal energy from outside of the building is transferred to the inside of the building using a liquid.