Insulation comes in many forms, the most common of which are shown below. Ideally, there is a vapor barrier between the house and the insulation to minimize moisture entering the attic from the house. This vapor barrier can be attached to insulation batts or is installed separately.
Decreasing the amount of heat entering the attic, by way of appropriate attic insulation, is another way to solve the problem of ice dams in the winter. Enough insulation in the attic also keeps your home cooler in the summer, keeping the sun’s heat on the roof from entering the house.