Armstrong offers a full-line of gas furnaces from 80% AFUE all the way up to 95% AFUE. In Armstrong’s higher efficiency range gas furnaces Armstrong uses staging to increase efficiency and staging ranges from 75% for low-fire to 100% for high-fire. Armstrong also uses variable speed motors in their higher efficiency gas furnaces. In Armstrongs lower efficiency gas furnaces Armstrong uses single staging with an aluminized heat exchanger that has a 20 year limited warranty. Other features in various Armstrong gas furnaces include a control system to ensure safe operation of the gas furnace, quiet operation of Armstrong gas furnaces, and energy star rated gas furnaces. Diagnostic abilities for better gas furnace troubleshooting Armstrong was founded in 1928 in Columbus, Ohio by Lennox, the maker of other air conditioning and heating products. Lennox sold Armstrong and then later reacquired Armstrong so Armstrong is officially owned by Lennox. Armstrongs manufacturers air conditioning and heating equipment in Orangeburg, South Carolina where the have a state of art facility desinged to produce quality air conditioning and heating products. Armstrong believes in quality and they run test every piece of equipment before it leaves its factory.