The SmartComfortâ„¢ VS 80 two-stage gas furnace features 80-percent AFUE efficiency and a variable-speed blower in a compact design, says the company. It can be installed in upflow, downflow, horizontal-left, or horizontal-right configurations. For horizontal applications, the rotatable inducer motor allows venting through the top or sides. The VS 80 furnaces come with a double-wall door designed to reduce operating noises and provide extra strength and durability, states the manufacturer. According to the company, these furnaces are designed with extra-spacious service compartments to give techs plenty of room to work. LP gas conversion kits are available.