Ice dams are a common winter problem that often gets discussed only after a major roof leak occurs. They cause icicles to form on the roof overhang and can inflate your energy bill. This condition occurs when the overhang of a house is covered with ice causing 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.

Here is how. When snow falls no outdoor area escapes it. Walks, driveways, garden, roof - they all get covered. Whereas walks, driveways and streets get plowed and shoveled, the roof remains covered in a thick bed of snow. This seals the roof and makes it more airtight. 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. Presto! Icicles. Unfortunately, some of the water freezes before it rolls over the edge. The freezing on the upper edge of the roof overhang occurs because that part of the roof is not as warm as the area over the attic. An attic area can become almost as warm as the living space below or adjacent to it. Result: a warm attic means melted roof snow. An ice cold overhang _ freezing both above and below _ means frozen water. As the snow over the attic melts, it runs down the roof, freezing when it hits the overhang, 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.

There are other negatives. Ice buildup can damage rain gutters. This can be a costly repair. 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: holes made for plumbing vents, furnace and ventilation flues and electric wiring. Also, make sure that your attic insulation is loose, not compacted, and that there is more than enough up there. Finally, look into eave heating devices 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.

And, there are special eave flashings that can be installed that will cause the ice to slip right off the eaves.

When we were kids our aunt and uncle had a cabin in the mountains that we visited each summer and 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 50 years we never saw the roof replaced once.

So take our advice, and next year experience dry conditions inside regardless of how wet and cold it might be outside.