Start at the top of your house in the attic. Air leakage and improperly installation can waste 20 percent or more of energy you pay to heat your home. Some attics are so leaky, it is as if you are leaving a window open and making your home heating system work overtime. Pay special attention to the attic; since heat rises, it can rise to your attic and right out of your home.
On a particularly cold day, take a thermometer to your attic and leave it there for about an hour or more. Compare the temperature on the thermostat to the temperature outside and inside other rooms. If the attic thermometer reading is more than 10 degrees Fahrenheit warmer than the outdoor air or closer to the inside temperature than the outside temperature, you have a problem.
Begin by replacing recessed lighting on your second floor. In many cases, recessed lighting allows heat to escape into the attic. Consider replacing the shades with tight can-like ones, as they are the only ones which can be insulated.
Seal holes where wires come out of the attic. Holes that bring cable, internet or telephone wires into a room are the primary place where cold air will enter a room. Insulate around these wires as best as you can.