Brad Diepholz talks about “Attic Ventilation”-part 5
Brad Diepholz found the following information.
This section I will be talking about dealing with the effects of ice dams.
Winter creates a special attic ventilation problem where snowfall and cold temperatures are common occurrences. The problem begins with the formation of ice dams or barriers formed of ice, that prevent water from running off the roof.
Ice dams can form when the following conditions exist:
-Warm air accumulates near the peak of an attic. This condition is much more common than people think. It occurs because most attics experience some heat loss from attic insulation.
-Warm air rises this is why the upper portion of an attic is always the warmest. Normally that pocket of warm air won’t result in problems until the following conditions are met.
-Lower areas of the roof remain cold. This is a common condition especially in the area just above the eave where temperatures may not be much higher than the outdoor air.
-If the outdoor temperature is well below freezing conditions this is favorable for the formation of an ice dam.
-A heavy snow cover accumulates on the roof. This snow accumulation not only provides the necessary moisture, it also acts as a layer of insulation preventing heat loss through the roof decking.
-As a result temperatures in the attic are typically warmer than they are on days when the roof is free of snow.
When all of these above conditions are met ice dams form quickly. Heat high in the attic causes snow to melt near the roof peak. The water from the melting snow flows towards the eave area where colder roof temperatures allow it to refreeze.
If conditions persist over several days this refreezing of snowmelt can form an ice dam. The weight of the dam itself can damage gutters and fascia. When it eventually falls is also can damage structures or shrubbery below.
Next time I will talk about how proper attic ventilation can help solve ice dam problems.
Typed by Brad Diepholz
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