Winter Problems: Ice Dams
From the California side of the Rockeys to Minnesota’s 10,000 lakes to New York harbor, their is a common winter condition that often only gets discussed after a major roof leak occurs. Do you know what it is? Here are a couple of hints: It is why icicles form on the roof overhang and it also indicates that your energy bill might be higher than you want it should be. Have you guessed what we are talking about yet. Here is another hint – it sounds like a swear word. Finally, you got it – ice dams. That is when the overhang of your house is covered with all that damn ice that causes melting snow to back up the roof and leak into the house.
From the calls we receive on our radio program it is apparent that ice dams are still a misunderstood phenomenon to many Americans. If you are from Los Angeles, Phoenix, New Orleans or Miami, you probably never have had occasion to experience a roof leak when everything outside was frozen. But it can and does happen.
And here is how. When snow falls there is no place that is sacred. Walks, driveways, garden, roof, it all gets covered. Where walks, driveways and streets get plowed and shoveled, normally, the roof remains covered in a thick bed of snow. This seals the roof and makes it more air tight. As the house is heated to keep occupants warm the heat escapes into the attic – heat rises – and the area becomes warmer and warmer. So much so that it melts the snow on the roof and the liquefied result rushes down the shingles and over the edge of the overhang – now you know where icicles come from. Unfortunately, some of the water freezes before it rolls over the edge – oops, no icicles here.
The freezing on the upper edge of the roof overhang results because that part of the roof is not as warm as the area over the attic. Believe it or not, an attic area can become almost as warm as the living space below or adjacent to it. Result – a warm attic equals melted roof snow. An ice cold overhang – freezing both above and below – equals frozen water. As the snow over the attic melts it runs down the roof – freezing when it hits the over hang – and creating a larger and larger wall of ice. Finally, the ice wall on the overhang (or dam) widens to the point where it reaches the edge of the attic. At this point the water remains liquid and the “ice dam causes it to back up over the attic where it can leak into the home. And all too often that is precisely what happens – water held back by the ice dam backs up and leaks into the home.
There are other negatives. Ice buildup can damage rain gutters. This can be a costly repair. We know, you don’t have gutters because it is just to damn expensive to keep repairing them each Spring.
By preventing ice buildup you might be able to save your house from being flooded during a freeze and add a little life to your gutters as well.
First, do not close off eave and roof vents in the winter. This traps the warm air that melts snow on the roof.
Second, make absolutely sure that all penetrations between living space and the attic are filled with foam sealant. You know, holes made for plumbing vents, furnace and ventilation flues and electric wiring, etc. Also, make sure that your attic insulation is loose (as opposed to compacted) and that there is more than enough up there.
Finally, look into eave heating devises such as eave tape. They are very low voltage, inexpensive to operate and if installed correctly can solve your problem with ice dams once and for all.
Whoops, we almost forgot. There are special eave flashings that can be installed that will cause the ice to slip off the eaves.
When we were kids our Aunt and Uncle had a cabin in the mountains that we visited once each summer and again in the winter. Every fall our cousins would mix graphite and shingle oil together. this concoction was used to preserve their wood shingle roof and to make sure that the snow would run off quickly the following Spring. In fifty years we never saw the roof replaced once.
So take our advice and next year count on dry conditions inside – regardless of how wet and cold it is outside. And, good luck!