How Ice Dams Form
During our Manitoba winters, snow builds up on the roof which accumulates with each snow fall if it is not removed.
From the furnace or fireplace, some of the heat is lost into the attic. With the snow on the roof acting as an insulator, the heat from the attic begins to melt the underside of the snow layer. The water then runs down underneath the snow until it reaches the eaves.
At this stage, the water is no longer kept in a liquid state from the heat of the attic, so the water freezes and forms a dam.
This cycle repeats itself, increasing the size of the dam as the water backs up further and further. Once the water reaches the heated part of the attic, it melts. This water works its way under the shingles, into the attic, through the insulation and eventually into your home.
What to Look For
#1 Ice dams start to form when you see a layer of ice forming at the eaves, right at the edge of the house. The accumulation of ice inside the eavestroughs will be visible from the ground. At this stage, you can remove the snow layer from the eaves—carefully. This removes the snow’s insulating ability, so the ice will melt when temperatures rise.
Do NOT use an axe, pick, blow torch or anything that will cause even more damage.
#2 Another thing to look for is icicles. Icicles are part of the ice dam where the water goes over the edge of the eaves and then freezes. This is a sure indication that the ice dam is getting worse and water is moving further up the roof.
You might be able to solve some of the problem by removing the snow at the eaves, but the results (if any) are dependent on the weather.
#3 When the ice dam is ignored, then water will be getting into your home. You will notice a discolouration of the corner of the ceiling where the ceiling meets the exterior wall. The water has seeped into the attic, wet the insulation and is pooling in the corner.
When there is enough water, the drywall will become wet, staining the ceiling. If left unchecked, the water will eventually cause the drywall joint tape to peel and the drywall will deteriorate.
In some situations, the water will run down the inside of the wall. You may see water stains at the bottom of the wall, above or alongside windows and exterior doors. Extreme cases will see puddles of water on the floor at the bottom of an exterior wall.
#4 The appearance of ice coming out of soffit vents, or in other exterior areas where ice should not be, indicates water has seeped into walls or into the soffits. The ice is also freezing the layer of the outside wall insulation.
When the temperatures rise, the ice will melt causing damage to the insulation as well as other unseen areas. Dangerous mold spores can result which leaves you and your family susceptible to serious health issues.
To prevent ice dams, there are some things you can do.
Keep your roof cold. If you can prevent heat from reaching the underside of the roof, the snow will not be able to melt. You can do this a few ways.
First, increase your insulation levels which decreases the amount of heat loss into the attic. Ensure the ducts in the attic are well insulated as well. Improving the insulation not only helps prevent ice damming, it also saves you money and improves your home’s comfort level.
Second, ensure that your attic has good ventilation. No matter how efficient your insulation is, SOME heat loss will still occur. When it does, good passive ventilation will allow the heat to escape where it is meant to. Have an adequate number of low vents in the eaves or soffits and high vents in the gable edge or along the ridge.
Before the first snow flies, clean out your gutters from leaves, dirt or anything that can prohibit water from draining properly from your roof. Clogged gutters often cause ice dams where the water has no place to escape.