please recommend gas furnace in Houston Construction, Home Repair, and Improvement Posted December 1, 2009 A contractor came in and said our gas furnace is too old. He also said there's CO2 leaking issue.I noticed that the heater had to work extremely hard in the winter last year. Can anyone please recommend an energy efficient model eligible for tax credit? Or any reliable contractor to use? Or any website I can go read more on this topic? My house is a 4-bedroom one story built in the 60s. The furnace is in the attic. Thanks in advance.