Usually there are  two major reasons why you need to replace your old furnace. The first is that your furnace has broken down or unsafe to operate, and it has been “red-tagged” or condemned by gas inspectors. If it is winter, and your house is getting colder quickly, you may not have the luxury of making a reasoned choice on what to buy next. The other situation is that your furnace is getting old, or your fuel bills are becoming too excessive to tolerate. In this case, you have the time to shop around and get the best furnace and fuel for your situation. This About Your House is written to address both situations. If you have a dead furnace and a chilly house, you will probably take some shortcuts in your selection process.