Extreme cold weather in our area and recent blog posts from experts such as Energy Vanguard out of Georgia about snow melt patterns on roofs (Snow on the Roof – The Poor Man’s Infrared Camera) reminds me of pictures I took last year of homes that had different snow melt patterns and ice forming on walls and over windows.  It even reminds me of a story from a friend who is a regional representative for one of the largest spray foam insulation manufacturers about a customer that was pretty upset that he had icicles on his gutter, even though they insulated the underside of the roof deck with the spray foam product.

Therefore it is time to resurrect the building science posts and go to my favorite resource for up to date building science research at Building Science Corporation.  So enjoy some advanced research on ice dams.

BSI-046: Dam Ice Dam

By Joseph Lstiburek

Ice dams are big problems because they often lead to water leakage into building assemblies, and more seriously, to falling ice that can be fatal (not kidding here) and to the weight of ice leading to structural collapse of roof overhangs and the shearing of deck assemblies when large masses of ice fall on them.

The strategy to control ice dams is fundamentally straightforward: keep the roof deck below freezing when the outside temperature is below freezing. Pretty easy you say? Not necessarily, as we shall see.

Historically, we have tried pretty much everything except the right thing to control ice dams. In New England where I live, older buildings use metal “slip” surfaces to get the snow to slide off the roof, preventing the ice dam from occurring at the roof edge.

Continue reading the article at buildingscience.com

View some of our own ice dam photos on our facebook page.