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Ice Dams Can Wreak Havoc on Your Chicago Roof If You Don’t Take Preventive Action

Those ice dams that form on the roof signal problems that could cause serious damage to the roof, the eaves and the fascia. The good news is that the dams are preventable, and resolving the problems that create them will improve the overall energy efficiency of your home. Not only will you stop structural damage to your home, you'll cut your heating bills by addressing the issues that cause them in the first place. 


Warm temperatures in the attic and clogged gutters promote the formation of ice along the roof's edge. The heat comes from your attic and indicates that it either lacks insulation, has air leaks from the ceiling, or inadequate ventilation. It's not uncommon to find all three of these conditions in a single attic.

Clogged gutters promote the formation of ice because they don't let the snow melt drain freely off the roof. Instead, the leaves and debris in the gutters hold the water, where it starts to freeze. As more snow melts, the ice continues to build, eventually resulting in ice dam formation. 


An icicle can break off ice dams at any time, damaging anything that's in its pathway as it drops to the ground. Besides personal injury, unchecked dams can damage the roof, the attic, its insulation and the fascia, causing any or all of these problems:

  • Water can seep into the underlayment beneath the shingles, eventually rotting it and the roof decking.
  • Moisture coming from the edges of the roof that comes into contact with the insulation inside the attic can promote mold growth. Damp and damaged insulation won't resist heat transfer as well and left unchecked, the mold can spread.
  • Ice melt that drains down the eaves and the fascia can accumulate in the siding or settle on any part of the wood framing, silently rotting it from the inside.


A thorough inspection of the attic and gutters will likely turn up the problems associated with the insulation, air leaks and inadequate ventilation. A peek in the gutters where the dams are forming may reveal debris that needs to be removed.

When inspecting the insulation, look for:

  • Uneven distribution of insulation throughout the attic. If you have loose insulation, it's possible for it to shift as air moves through the attic on windy days. Smooth the insulation out. If someone has disturbed a layer of batt insulation, you can either add more or move the disturbed piece back.
  • Inadequate insulation. The U.S. Department of Energy recommends from 16 to 20 inches of fiberglass or loose fill insulation for homes in this region to prevent heat transfer from the ceilings and ice dams.

You can spot problems caused by air leaks by looking for:

  • Ductwork for your HVAC system that runs through the attic. This ductwork should be insulated and tested by an HVAC professional for leakage. Besides warming the attic and laying the groundwork for ice formation, you could be losing a good deal of air you've paid to heat in the attic.
  • Any recessed lighting fixture that enters the attic. These fixtures are notorious for having air leaks around them. The heat from the light bulbs and the indoor air will enter the attic, increasing the temperature of the roof deck.
  • An attic hatch with no insulation or weatherstripping around its edges.
  • Bathroom or kitchen ventilation fans that exhaust into the attic. The vent stacks for these fans should exit through the roof, but if they terminate in the attic, the warm, humid air you exhaust will cause both winter ice dams and other moisture problems year-round.

Ventilation issues aren't uncommon in attics. Ideally, the temperature inside the attic during the winter should match the outdoor temperature to prevent ice dam formation. Use the following formula to estimate the amount of ventilation your attic has and the amount you need:

  • Multiply the length and width of the attic and divide by 300. The result will give you the total square feet of natural ventilation you need. Divide that number by 2.
  • Find the square feet of the existing vents and multiply by 144. You should have at least one soffit or eave vent and a ridge vent. Their combined sizes in square inches (144 inches per square foot)should match or exceed the total amount of ventilation your attic needs.

If you'd like more information about dealing with ice dams and their prevention, contact to find a trusted HVAC contractor in Chicagoland, northwestern Indiana or southeastern Michigan today.

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