What Is Ice Damming?

A key point to remember when considering ice dams - the temperature should be the same inside the attic as it is on the exterior of the home if the attic is insulated. 

Ice damming occurs in the following situations: 

  1. There is not enough insulation and poor air infiltration between the attic and the living space. This causes warm air to rise and go into the attic. 
  2. The warm air in the attic melts the snow on the roof deck. 
  3. The melted snow begins to run off the roof. 
  4. Once it hits the soffit area it begins to freeze. It freezes over the soffit because the warm air that was under the roof is no longer there and the cold air under the soffit begins to freeze the melted snow. 
  5. As the snow accumulates on the roof time-and-time again after each snow fall, the ice dam gets bigger. 

A common misconception heard from homeowners every year is, "I have ice and water shield on my roof - so I shouldn't get ice dams." 

Ice and water shield isn't made to prevent ice dams, it is used to help stop ice and water from infiltration into the roof once ice dams form. It does not prevent ice dams, but rather protects you from ice dams once they form. 

How are Ice Dams prevented? 

Stopping ice dams is simple, in principle: keep the entire roof the same temperature as the eaves. You do that by increasing ventilation, adding insulation, and sealing off every possible air leak that might warm the underside of the roof. Using the Deck-Air, Model DA-4, is a solution for homes with inadequate intake ventilation.