I am not sure what the temps were at that particular time, but typical winter days here are highs in the low 50's or upper 40's with lows near or below freezing. Several weeks last winter the lows were in the single digits.
I've worked out some skirting already, and spent the better part of today putting plastic over windows.
The furnace has not been serviced since I bought it in December of 2007 (if then.)
I am planning on taking a good look at it tomorrow, have been dreading it as it is under the reefer with no other access that I can find.
The only enclosed part underneath is the fresh water tank, and that is just fiberboard (insulation too?) that has a duct diverted to it.
Temps will be dropping into the upper 40's at night by Monday here, so I am trying to get as much done as I possibly can.
Oh, and I also replaced the original thermostat with a Hunter digital (not programmable) just before summer, so don't know if that will help any yet or not.