CBHvac wrote:

"j j" wrote in message
...

our furnace is probably 50 years old. it's a big cast iron thing.

everyone we asked told us not to change it because new furnaces have
crappier construction.


Then you are asking the wrong people.
Granted, they dont make tanks anymore.

Hi,
Big cast iron thingy alright but at what efficiency? Maybe your dollar
is going up the chimney more than heating your house.
How about doing some cost anaysis?
Tony