Look up at your eavestroughs in winter, and you may see icicles hanging over them like a partly frozen waterfall. However, you can’t blame your gutters. They are just in the wrong place at the wrong time. Take them down and the ice dams will keep building.

How and Why Ice Dams Form in Winter

Your outside roof surface is not the same temperature throughout. Warm air from the rooms below can transfer warmth to the attic space above, and keep the temperature below freezing.

Meanwhile, the chilly outside air beneath the eaves keeps them well below freezing in winter. This accounts for the temperature differential across the roof, and is the dynamic behind the formation of ice dams over eaves.

What Happens to Trigger Ice Dams

Snow naturally accumulates in winter on roofs. However, their pitch should be sufficiently steep to limit the quantity. Meanwhile, the householder turns up the heat on the thermostat, increasing the warm air finding its way into the attic space by convection.

As the temperature rises directly below the roof, this warms the outer surface to the point where the snow starts to melt. This melt trickles down the roof until it reaches the ice-cold eaves, where it freezes again.

We have witnessed the birth of an ice dam before the melt reached the eavestroughs. The ice dam will keep growing throughout the cold snap, unless we do something proactive about the underlying cause.

Are Ice Dams Really a Problem?

Unfortunately they are. They can super cool the shingles beneath them, and make them crack. Trickling water can find a way past, and create damp problems. However, the biggest danger is the risk of an icicle breaking off what is effectively a glacier, and crashing to the ground.

Three strategies can help prevent icicles, or at least limit their extent:

1… Tackle the problem at source by turning the thermostat down, and wearing warmer clothes inside the house

2… Improve the insulation on top of the ceiling, by finding and closing out weak points especially the access hatch

3… Boost your attic ventilation so that any warm remaining harmlessly leaves the roof space

This information comes to you with compliments of Valiant Exteriors Ltd. We are local Calgary experts in roofing, attic insulation and venting, eavestroughing and siding. Please give us a call on (403)829-1661 if we can assist.

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Ice Dam on Roof: Image Brocken Inaglory BY CC 3.0