If you own an older home, the walls are probably only 4 inches thick. That means that they have only R 12 insulation. There is a couple of ways to cut energy costs by reducing heat loss through your outside walls.
If you are intending to renovate the inside of your house, then you can take out the old panels or drywall off the walls and add 2 inch ridged foam panels to the walls before putting on new drywall.
The other way to insulate the walls is to add 2 inch ridged foam panels to the outside of the wall. You would have to replace the siding as well. Either way this would bring your walls up to R20.
Cut energy costs by making sure your attic is properly insulated and vented. Because heat rises, the attic is the first place that you should check to make sure that it’s adequately insulated. There should be at least 12 inches ( preferably 15 inches ) of insulation in the attic.
Insulation is given an R value to indicate how good it is. For every 1 inch of insulation there is an R value of 3. Therefore 15 inches of insulation is R 45. That is the minimum you should have to keep the heat from escaping. The temperature in the attic should be about the same as the temperature outside.
A properly vented attic will decrease the possibility of condensation moisture to collect on the rafters or on the inside of the roof. One or more whirlybirds and a few vents should do the trick. Blown insulation is widely used as attic insulation for several reasons. A professional home insulation contractor can quickly blow in one continuous blanket at the proper depth to achieve the recommended R45 insulation for attics. Many contractors offer pricing that includes the insulation itself and installation: usually less than the retail price homeowners would have to pay for the insulation alone. In addition, a properly installed continuous blanket of blown insulation does a better job at at stopping air leaks and subsequent heat loss.
Blanket or batt insulation meticulously installed will be better than a continuous blanket of blown insulation. However, any flaws or errors during installation will decrease the performance. If you have a trap door in the ceiling to get into the attic, make sure it also is properly insulated. Build a cardboard box 15 inches high around the inside edge of the door and fill it with insulation. Make sure there is a good seal where the door meets the ceiling.
