Ice dams are not very common in Seattle.
I know in other parts of the country they are a huge problem. Many older homes–and lots of newer homes–are improperly designed and improperly built to prevent them.
On top of the tremendous amounts of energy loss they represent, people spend thousands of dollars getting the damage they cause fixed, or on futile attempts at clearing them from the roof. They mean falls from ladders, emergency room visits, freezing ones butt off in the worst possible weather conditions, emptying buckets in the living room and visits from insurance adjusters.
Every time it snows–or even frosts hard–I get to see one of the things that can cause ice dams–visibly demonstrated on my neighbor’s roof.
The bare spot below the left roof vent shows where there is a can light in the vaulted ceiling.
Can lights in vaulted ceilings can result in lots of heat loss because they act like little chimneys carrying heat to the roof surface (moisture too if they are older types of can lights). As the snow is melted off the roof it can run to the cold eaves and re-freeze where it could create an ice dam if the climate is cold enough and the winter long enough. Here is Seattle where we typically only have winters that wish they were winter–this rarely represents more than just evidence of heat loss.
Makes you wonder how much energy an non-air-tight can light can waste over the life of a home.
By Charles Buell, Real Estate Inspections in Seattle
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