How Attic Ventilation Helps Solve Ice Dam Problems.

When homeowners set out to eliminate ice dams, their typical response is to add more insulation to attics.  But no amount of insulation, if used alone, can eliminate the formation of ice dams.  An efficient attic ventilation system must be part of any solution.

A properly designed ventilation system creates a "cold roof" - a condition where the roof temperature is equalized from top to bottom.  An equalized roof temperature, in turn, helps eliminate the conditions that lead to the formation of ice dams.

By now you probably know how ventilation creates a cold roof:  it allows a flow of air to sweep along the underside of the roof sheathing, minimizing temperature differences. You also may have a valid question to raise:  Aren't we talking about a uniform flow of cold air sweeping through the attic?

Exactly, and that's why ventilation alone isn't a complete solution either.  For maximum comfort, reduced structural damage and optimum energy conservation, ventilation must be used with a waterproofing shingle underlayment and, of course, with insulation.  Ample insulation is required to minimize heat losses, and high-efficiency air movement is required to remove any heat that enters the attic. 

To reduce the possibility of ice dams, use a three-step approach:

• Install adequate attic ventilation.  Because ice dams form when a roof has warm upper surfaces and cold lower surfaces, the solution is to equalize temperatures over the entire roof.  The most effective way to equalize temperatures is to create a cold roof.  To do that, you need a well designed attic ventilation system that will suppy airflow along the entire underside of the roof deck.  That's critical, because only a uniformly distributed airflow can reduce variation in roof temperatures from peak to eave.  One of the most efficient and effective systems (from both cost and performance standpoints) uses ridge vents and an evenly distributed layout of intake vents.
• Install adequate attic insulation.  Attic insulation serves two purposes.  First, it reduces heat loss from a home's living quarters.  Since that heat loss is a key factor contributing to the creation of ice dams, stopping it at its source is critical.  Second, adequate attic insulation diminishes the energy impact of having cold air flowing through the attic.  When installing insulation - or checking existing insulation - be sure to install adequate amounts around electrical fixtures and wiring and plumbing chases.  These areas often contribute to significant heat loss.  With existing insulation, also check for water damage and for areas compressed by foot traffic or stored objects.  
• If possible, install waterproofing shingle underlayment (WSU).  Even the most efficient attic ventilation system may not be enough to eliminate all ice dams.  A combination of weather conditions, roof pitch, building orientation and other factors may allow ice dams to form under certain conditions.  If that happens, a WSU barrier can minimize - and possibly eliminate - water infiltration into the building structure.  

If you are uncertain as to whether your attic ventilation and/or insulation are adequately protecting your roofing system and your home, contact us by visiting our website: www.precisionroofingmi.com or call (517) 393-9386.  The appointment and quote are both FREE!