Joe wrote:
....
Well, I don't mind spending money on new windows but I'm going to feel
foolish if my fuel usage stays static with the new windows and the
real problem was the walls. How can I find out where the heat is
escaping?

Follow ransley's advice and get an energy audit. Your PowerCo may have
it as a service or the heating fuel source distributor...

If it's a 50-yr old house, it's almost certainly under-insulated by
today's standards unless it has been relatively recently upgraded
significantly. Of course, you can look at attic, basement, etc.,
yourself and see what's there. The walls and finding the air leaks,
etc., are where it can really help plus a good inspector will spot any
unique features of the particular building.

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