I go to Florida in the winter. My house in Minnesota has hot water
heat (natural gas) and a "boiler" with 3 zone valves that are less
than 10 years old heating 2400 sq. ft. It has mercury thermostats
that are also just a few years old. Last winter our gas bills were as
high as $200 a month even though the thermostats are all the way down
(55 degrees). This year they will be higher. I've read threads about
antifreeze in the hot water heating system (sounds like
there can be problems) and I realize I could close the house (drain
plumbing and hot water system) but I've heard horror stories about
walls cracking, etc. (it can get down to -40 here!). Someone told me
to tilt the thermostats to get below 55 but this seems difficult to
control.

Any ideas on how I could save some money this winter? I'm certainly
willing to spend some money to save some.

Thanks in advance.