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How ventilation helps solve attic moisture problems and prevents ice dams.

Monday, January 2nd, 2017 by Amanda Mayes


Although the problems of attic heat and moisture have different causes, they share a common solution: a high-efficiency ventilation system that allows a uniform flow of air to sweep the underside of the roof sheathing.  In warmer months, such a system exhausts hot air from an attic; in the colder months, it exchanges warm, moist air with cooler, drier air.  In both cases, the result is the same: less damage to the home.

Winter creates a special attic ventilation problem in areas where snowfall and cold temperatures are common occurrences.  The problem begins with the formation of ice dams - literally barriers formed of ice - that prevent melt water from running off a roof.

How ventilation helps solve attic moisture problems and prevents ice dams - Image 1

Ice dams can form when the following conditions exist:

  • Warm air accumulates near the peak of the attic.  This condition is much more common than people think.  It occurs because most attics experience some heat loss from attic insulation.  And because warm air rises, the upper portion of an attic is always the warmest.  Normally, that pocket of warm air won't result in problems - that is - until the following conditions are met.
  • Lower areas of the roof remain cold.  Once again, this is a common condition, especially in the area just above the eave, where temperatures may not be much higher than the ambient outdoor air.  If the outdoor temperature is well below freezing, conditions ae 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 sheathing.  As a result, temperatures in the attic are typically warmer than they are on days when the roof is free of snow.

When all three 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 toward the eave area, where colder roof temperatures allow it to refreeze.  If conditions persist over several days, this re-freezing of snow melt can form an ice dam.

The weight of the dam itself can damage gutters and fascia.  When it eventually falls, it also can damage structures or shrubbery below.  But the greatest damage occurs when the water pooling inside the dam begins to infiltrate under shingles.  The shingles themselves are damaged - if not destroyed.  Far more serious, however, is the damage caused at the plateline area.  Insulation can be soaked, reducing its effectiveness.  Plus water can infiltrate into both exterior and interior wall cavities, leading to structural damage and the deterioration of painted surfaces.  At the very least, mold and mildew can form, creating unpleasant odors and mold spores, resulting in poor indoor air quality.  

We receive many calls this time of year regarding ice dams and roof leaks.  These are serious problems, and, if neglected, can cost homeowners a lot of money in repairs.  We encourage you to give us a call if you are seeing ice dam formation along your eaves and gutters.  One of our consultants will stop by and take a look at your roof and attic in order to determine what the problem may be.  Our professional roofers work during the winter months so don't wait until Spring!  Contact us today at www.precisionroofingmi.com or give us a call at (517) 393-9386.  The appointment and quote are both FREE.

 

 

 

 

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Precision Roofing Services
319 Clinton St
Lansing, MI 48906
1-517-336-3555
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