INSULATION, VENTILATION Protecting your home

Here's what you can do to prevent ice dams:
Upgrade your attic insulation. The goal is to prevent heated air from rising up from the living areas and out through the roof. If you're putting insulation between rafters, be sure to add baffles so air can flow up, said Mickey Plank of M.R. Plank Roofing Co. In addition, Chris Koehler of Squires Roofing Co. noted that attic insulation should have a vapor barrier, which stops moisture in the air from entering the attic and condensing.
Improve your attic ventilation. Vents allow cold air to flow into the attic from outside and let warm air escape. If the attic has too few vents, or if the vents are blocked, this air flow is restricted and the attic can get too warm.
Clean gutters and downspouts regularly. Keeping gutters free of debris is important year-round, but pay special attention in the fall, when the leaves are falling. You may even need to clean the gutters and downspouts twice in autumn to keep them running freely.
If you can reach your roof easily and safely, use a roof rake to clean off the snow. Do it soon after the snow falls, before it has a chance to start melting.
If you're building a house or having a new roof put on, consider installing an ice and water shield, Plank advised. It's a rubberized membrane that covers the roof decking beneath the shingles and extends 3 feet up the edge of the roof to discourage leaking from ice dams. The material is self-healing, so it forms a seal around the shanks of the roof nails, he said. The membrane can be added to a roof, but that requires tearing off shingles, he said. It isn't foolproof, however. Bud Housley of Housley Roofing and Spouting said he's seen ice dams push underneath the rubberized layer.
Electrically heated cables are another option, but neither Plank nor Housley recommend them. Plank said they wear out quickly, and he's leery about the use of electricity around water. "Heck, I've seen those things smoke," he said. The cables are attached to the roof near the edges, on top of the shingles. They don't prevent ice dams, Plank noted, but merely melt channels in the ice to help runoff escape.
Source: Knight Ridder Newspapers