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Got Ice dams? Anchor Insulation is here to assist you.

*What is an Ice dam?

An ice dam is a ridge of ice that forms at the edge of a roof and prevents melting snow (water) from draining off the roof. The water that backs up behind the dam can leak into a home and cause damage to walls, ceilings, insulation, and other areas.

 

*What causes Ice dams?

There is a complex interaction among the amount of heat loss from a house, snow cover, and outside temperatures that leads to ice dam formation. For ice dams to form there must be snow on the roof, and, at the same time, higher portions of the roof's outside surface must be above 32°F while lower surfaces are below 32°F. For a portion of the roof to be below 32°F, outside temperatures must also be below 32°F. When we say temperatures above or below 32°F, we are talking about average temperature over sustained periods of time.

The snow on a roof surface that is above 32°F will melt. As water flows down the roof it reaches the portion of the roof that is below 32°F and freezes. Voila! - an ice dam.

The dam grows as it is fed by the melting snow above it, but it will limit itself to the portions of the roof that are on the average below 32°F. So the water above backs up behind the ice dam and remains a liquid. This water finds cracks and openings in the exterior roof covering and flows into the attic space. From the attic it could flow into exterior walls or through the ceiling insulation and stain the ceiling finish. 

 

*What you can do about Ice dams and How to prevent them.

  • Remove snow from the roof. This eliminates one of the ingredients necessary for the formation of an ice dam. A "roof rake" and push broom can be used to remove snow, but may damage the roofing materials.

 

  • In an emergency situation where water is flowing into the house structure, making channels through the ice dam allows the water behind the dam to drain off the roof. Hosing with tap water on a warm day will do this job. Work upward from the lower edge of the dam. The channel will become ineffective within days and is only a temporary solution to ice dam damage.

 

*Preventing Ice dams

First, make the ceiling air tight so no warm, moist air can flow from the house into the attic space.
After sealing air leakage paths between the house and attic space, consider increasing the ceiling/roof insulation to cut down on heat loss by conduction. 

 

At Anchor Insulation we recommend Icynene spray applied foam to eliminate ice dams.

Conditioning the attic space with spray foam will eliminate ice dams as it provides a continuos air barrier and seals the attic. 

Rather than the traditional way of insulating the attic floor it is much easier to condition the attic space with spray foam insulation. There are far too many areas to air seal at the attic floor. Recessed lights, skylights, complicated roof designs, and heating ducts in the attic will all increase the risk of ice dam formation.

To prevent ice dams you need a 100% effective air barrier through the ceiling. There should not be any air leakage from the house into the attic space! Spray applied foam provides this and many more benefits over conventional insulation products.

At Anchor, we use spray foam products by Icynene and we are a licensed Icynene dealer. Below is a great video from them regarding ice dams.

 

 

 

 

 *Information from University of Minnesota