Lennox 20066501 Combustible Floor Base. Lennox goal is to provide contractors with high-quality HVAC solutions and replacement parts. This system includes changes and inventory updates to ensure peak performance. Lennox has a large line up parts and products for high-efficiency packaged rooftop units, split systems, HVAC controls, furnaces and indoor air quality products. This Combustible Floor Base is designed to be installed where the duct-work will run through floors and ceilings. The fiberglass coating and sheet metal frame are ideal for the transportation of the air coming from the unit to the rest of the house.