Some insulation in the attic will help. Putting a LOT there is an
inefficient use of money, unless you do other high-loss areas at the
same time. If, for instance, you've got single-pane windows,
you may well be better off putting your money into storm windows
than into fiberglass in the attic.


Insulating the attic is probably the best thing to do. Heat rises, of
course, and most heat is lost out of the attic. Replacing windows is a fad
that doesn't really help too much, unless the windows are leaking air.
Definitely start in the attic.


Heat doesn't rise, hot air rises. If you trap the air, the heat will
go up, down, and sideways with equal enthusiasm.
Restricting the airflow upward is the single most important move.
Since you can never completely shut that off, a thin layer of
insulation in the attic will do double duty further restricting
airflow. But beyond that, the most effective place to put
insulation is where the least insulation is now. If you have
a choice between putting and extra R12 in a ceiling that's already
R12, and putting R2 worth of insulation in the same amount of
wall that's currently R5, for the same price, you should insulate
the wall. Do the math: 100 sqft of ceiling at R12 passes 8
BTU/Hour/degree. Adding R12 changes that to 4 BTU, saving you
4 BTU/Hour. The same amount of wall at R5 passes
20 BTU/Hour/degree, and adding R2 changes that to 14, saving
you 6 BTU/hour.