Did you know that ice dams are caused by poor ventilation and improper insulation? Did you also know that poor ventilation, improper insulation and ice dams will lower the life expectancy of your roof by as much as half the estimated shingle life span? A good roofer will point these things out to you and a new roof is a big expense so to get the most out of your new roof make sure you have adequate ventilation and insulation which should also eliminate any ice dams!