I have a Trane XL80 60K furnace with no air conditioning. It is about 15 years old. I want to upgrade the furnace to a 90K which I remember was supposed to be easy to do by simply replacing the jets with larger 90k units. But now the furnace installation company (original factory approved installer) says they never heard of such a thing. We bought this 60K unit only because we knew it could be "converted" to a 90K inexpensively, because we knew we were going to remodel in the future. We are now building the second addition since installation and are going to add the air conditioning unit and the heat pump for it, but we also need more heat for these cold Ohio winters. Do you know anything about the upgradability of this furnace? Thanks. Bob.

Go with a new bigger furnace. Your old unit is 15 years ols already and getting close to replacement time anyway. You could also use a bigger unit because you will need more blower capacity for the new addition and now would be a good time to rethink all of your HVAC needs.