Ice Back up on Roofs

Ice problems on roofs can best be understood by examining the anatomy of an ice dam. Typically an older house will show signs of melting snow that after awhile will freeze on the overhang and cause icicles.

These pretty cute formations can create havoc with your shingles. As seen in the diagram below, the trapped heat in the roof area above the living area will melt fallen snow. As it melts it forms ice as it nears the unheated edge of the roof. The more that the snow melts, the more ice you will have. This situation continues as long as conditions exist.

If this melting continues, it will eventually hold water on the shingles and leak through into the insulation and through the ceiling.

How you avoid this scenario is really quite simple in most houses. There should be a way to open or ventilate the overhang on the house thus allowing fresh outside air to come into the attic. This air will be allowed to exhaust through the vents at the top of the attic. By doing this, the roof should maintain the temperature of the outdoors. If it is freezing outside the roof will not melt snow. If it is over freezing (+32°) then you won’t be forming ice anyway.

The real twist to this story comes in at the point where you have a house that doesn’t readily conform to this scenario because it is either not possible to ventilate the eave of your house or there isn’t an overhang. Sometimes homeowner’s don’t even have upper roof vents for exhaust air. Quite often we can add a ventilated drip edge to the eave that has been proven to perform very well in eliminating ice build up.

When an attic/roof is particularly hard to ventilate, we can install power driven roof and gable vents to pull out unwanted warm air from your attic. There are options for reducing the heat build up in your attic during the summer. There is also a humidistat control that allows the fan to run when the humidity level reaches a high level. This control will work in the winter by eliminating warm air from the attic when temperatures rise over 32 degrees in your attic.