Why Do Ice Dams Keep Coming Back?
If ice builds up along the same roof edges every winter, the problem may have more to do with what is happening inside the attic than with the ice itself.
Ice dams form when snow melts on a warmer part of the roof, flows toward a colder eave and refreezes. Heat loss, air leakage, insulation coverage, attic conditions, ventilation and winter weather can all influence that cycle.
See the Melt-and-Refreeze Cycle in Action.
This short animation shows how heat reaching the roof can begin a cycle that ends with ice building along the colder eaves.
Ice Dams Begin Before the Water Reaches the Eave.
The visible ice at the edge of the roof is usually the final part of a process that begins higher on the roof.
Part of the Roof Warms
Heat reaching the roof deck can warm areas beneath the snow enough to begin melting it, even when outdoor temperatures remain below freezing.
Meltwater Moves Down the Roof
The water flows toward the lower roof edge and overhang, where the roof surface may be colder than the area above.
Water Refreezes at the Eave
Repeated melting and refreezing can build a ridge of ice that traps additional meltwater behind it.
The Ice Dam Is the Symptom. The Warm Roof Is the Clue.
When ice dams return in the same areas year after year, the more useful question is what may be causing those portions of the roof to warm enough to melt snow repeatedly.
Several Attic Conditions Can Contribute to Uneven Roof Temperatures.
Recurring ice dams are rarely a reason to assume that one single component is responsible. Several parts of the attic and building envelope may affect how much heat reaches the roof.
Air Leakage Into the Attic
Openings around wiring, plumbing, framing and other penetrations can allow warm indoor air to move into the attic and reach the roof assembly.
Thin or Uneven Insulation
Low, missing, compressed or disturbed insulation can create areas where more heat transfers from the living space toward the attic and roof deck.
Attic Layout and Construction
Framing, roof geometry, mechanical equipment, access openings and other building details can influence where heat collects or moves through the attic.
Attic Ventilation
Ventilation is another part of the overall attic system and should be considered alongside insulation and air sealing when recurring ice dams are being evaluated.
More Insulation Is Not Automatically the Whole Answer.
If warm air is leaking into the attic or other conditions are contributing to uneven roof temperatures, simply adding insulation may leave part of the underlying problem unchanged.
The Same Ice Dam Often Returns Because the Same Conditions Remain.
When ice repeatedly builds in the same place, it can be a clue that the roof temperature pattern beneath that area has not changed.
If heat continues reaching one portion of the roof more than another, snow may keep melting in the same area and refreezing near the same eave. Removing the visible ice may solve the immediate buildup without changing what caused it.
Repetition Is Useful Information.
The location of recurring ice buildup can help Grand Traverse Insulation understand which attic or building conditions may deserve a closer evaluation.
Patterns Worth Noticing
Find Out What May Be Causing Them to Return.
Grand Traverse Insulation can evaluate attic insulation, air leakage and other building conditions that may be contributing to recurring ice dams.