I own 2 homes, my primary residence and a small vacation home. Both in Illinois and have relatively similar climates.
Primary residence is ~2500 sq. ft. raised ranch, average insulation, new windows and heated to 68 degrees via a 15 year old nat. gas forced air furnace. We also have nat. gas water heater and stove.
Vacation home (this is only our 2nd year in this house...so I'm not overly familiar with all the details), ~1400 sq ft. ranch with full finished basement (~1400 includes basement), average insulation...ancient/crappy windows and is kept at 50 degrees during the winter via a 1996 nat. gas boiler with 3 heating zones (1 downstairs, 2 up). We also have nat. gas water heater.
We just went through a particularly cold strech here in Illinois...and during this period the vacation home actually used more natural gas (by actual Therms...not just by price) than my primary home...which floored me. I had thought that nat. gas boilers are more efficient and it seems like a 14 year old boiler isn't THAT old.
So, just generally speaking, where do I start to look? Can windows and doors make THAT big of an impact? I can't imagine how the previous owner could have even survived the gas bill at full-heat 24/7. Is the theory that a 50 degree home should take less heat than a 68 degree home somehow flawed?