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Ice Dam Prevention Techniques

11 January 2020

Our team answers homeowner questions every weekend on WCCO 830 AM from 9:00 am-10:00 am.  Have your most pressing home improvement questions addressed by calling or texting 651-989-9226.  Here’s the must-know information our COO, Andy Lindus, shared on 1.11.20.

The show’s first caller was Robin from Forest Lake, MN.  His home was built in 1964.  Awhile back, he’d had an insulation contractor blow-in an additional foot of insulation into his attic.  The contractor had also made enhancements to the home’s ventilation.  Last year, for the first time, Robin had experienced ice dams on his home.  He was curious to know if the -50° temperatures last year were the culprit or if his home needed additional insulation and ventilation.

ice dam

While diagnostic testing is the best way to determine this, it’s possible the home’s ice dams were due to the extreme temperatures of the previous winter.  When exterior temperatures reach -50° the pressure difference between the inside and outside of the house are tremendous.  This accentuates the stack effect.  This means that cold air is traveling down your walls from the attic needs to be replaced.  Frequently, this air is replaced with the warm air in your house.  When the warm air travels upward to the attic, it quickly comes in contact with cold surfaces in the attic, causing frost in the attic and heat loss on the roof.  When a roof experiences heat loss, the snow on the roof will melt, leading to ice dam formation.  If ice dams continue to form on your home year after year, it’s wise to consult with a reputable insulation and ventilation contractor that can also evaluate if the attic ventilation is working as a system and that elements are not competing.  Simply adding more insulation to an attic without taking a hard look at ventilation and attic air sealing can create more problems than it solves.

insulation and ventilation

Quality insulation contractors have an array of diagnostic tools that they can use to understand where a home is losing energy.  In addition to smoke sticks and infrared imaging, blower doors can also be used.  A blower door looks like a giant screen door with a fan attached to it.  The fan creates pressure that is needed to show where air infiltration is taking place.  Blower door testing works the best at the times of the year when a home’s interior temperature is similar to the exterior air temperature.

Learn More About Blower Door Testing: 


When the walls within a home need insulation, it’s unwise to add spray foam insulation with the wall sheathing still in place.  This can lead to numerous voids being left unaddressed.  Insulation can also be present that prevents the spray foam from expanding evenly, which will lead to the creation of hot and cold spots within the insulation.  This encourages the formation of condensation.  When this happens on the inside of a wall, dry rot and mold quickly commence.  When insulating a wall, it’s best practice to remove the sheathing and all the old insulation before proceeding.  The home’s siding can also be removed so that air sealing and insulated house wrap can be added.

Listen to the Entire Show Here: 

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