Recently, Gregory Bublitz was asked to contribute to an article in the Milwaukee Journal Sentinel about ice damming. Here it is in its entirety.

What can be done to prevent ice dams from forming?

There are ways to treat the causes and ways to treat the symptoms said Greg Bublitz of GSB Companies LLC in Delafield, WI. "Sometimes the solutions requires a combination of both," he said. "Understanding why the ice dam is forming is critical to preventing it."

Ice dams form when snow on the roof melts even though the outside temperature is below freezing. The melted snow flows down the roof until it is exposed to the freezing temperatures, such as at the roof edge or gutter. It may also collect in valleys on the roof. Repeated cycles of this melting and freezing forms a ridge or dam. This traps water behind it and forces water into areas where it normally would not flow. Additionally, the icicles that form can pose a safety risk.

What causes the melting cycle in the first place? "Conditioned air from the living space escaping into the attic space is a major contributor to ice dam formation," Bublitz said. This can take place through any penetration in the ceiling - can lights, attic access doors, exhaust fans, knee walls, openings around chimneys, etc.

"Poor levels of insulation allow heat to be conducted into the attic, resulting in additional warming," he said. Solar gain, which is the roof surface being warmed by the sun, and temperatures fluctuating above and below freezing can melt the snow, providing the water that builds ice dams. "Also, improper ventilation of the attic plays a role."

So how can ice dams be prevented? If they are caused by what is happening inside the home, Bublitz said to treat those causes first. The "absolute first step" he said is sealing all or as many as possible, air bypasses that are allowing conditioned air to enter the attic space. "This can be done as a DIY project, but it may be a good idea to consult a qualified contractor," he said. "Spray foam insulation is a great product to seal the air bypasses. Without doing this first, adding insulation or improving ventilation, will have little effect. The most common mistake many make when trying to solve ice dam problems is to skip this step."

Are insulation and ventilation up to current building codes? Another common mistake some make is adding power ventilation on difficult-to-ventilate homes. "This can draw air form the living space, driving up energy costs and having little effect on ice dam prevention," he said.

"If your ice dams are caused by what is happening outside, what has been done on the inside will have little effect," Bublitz said. "Even new homes built to current codes can suffer." When the architecture is more complex, homes may have higher roof sections exposed to the winter sun with lower sections shaded. Good roofing practices can go a long way in preventing the leaking. Waterproofing underlayment can stop melt water from entering the structure, but it is not foolproof, and it does nothing to stop ice dams and icicles from forming.

"Heat cables are often used to prevent ice dams - treating the symptoms - when other remedies have failed," he said. Heat cables are effective in combating ice dams caused by external forces. "They can keep ice from forming in the first place. Good design is essential. The most common application is zigzag heat tape, which is strung along the eave. As we have seen this year, this application has struggled to keep up."

There are also radiant panels made of aluminum with commercial grade heat cables embedded in them. These are placed in valleys and at the eaves, along with heat cables in the gutter bottom and downspouts. "They are more effective at preventing the buildup of ice and have a longer lifespan," he said.

The key to ice dam prevention is understanding the cause of the problem. "Homes differ, so the cure for your neighbor may not work for you, Bublitz said. "If you are unsure, there are contractors that specialize in determinining the cause and recommending the solution."

Answers to "Ask the Contractor" are provided by members of the Milwaukee/NARI Home Improvement Council, Inc. Questions can be addressed to: Ask the Contractor, 11815 W. Dearborn Ave. PO Box 26788, Wauwatosa, WI 53226