The EPA’s Energy Star program adds that adequate insulation is one of the most cost-saving home projects a homeowner can undertake. One way to tell if your insulation is not performing properly from the exterior of a house in the winter is the development of large ice dams, or large icicles that hang down off of the overhang on your home. If your home heats up quickly in the summertime, it is a sign that the insulation is not keeping the heat out of the house and it may be compromised.