What is an Ice Dam and How Does it Form?
Initially I thought an ice dam was formed by blocked gutters; nope! While dams can extend into a gutter if the conditions permit, it’s all a matter of proper and improper insulation and ventilation. In a perfect world, the melting ice and snow would flow off into your gutters and away from the house. However, when outside air temps are very low, the edge of the roof stays below freezing and the water refreezes where the interior roof surface is not being warmed by the attic. This refreezing gradually creates a “dam”, a growing heap of ice that blocks the path of melted snow. Once the dam is large enough, the melted snow that pools up behind it can force its way back under the roof shingles and then leak into your home!
How do you Prevent an Ice Dam?
Since the main cause of ice dams is an overly warm attic, a good start is adding insulation to lower the overall temperature. There are limits to adding insulation, whether it’s laid over existing or blown in. Once the R-value is reached, the amount will not show an appreciable decrease in heat loss per dollar spent. Owens Corning’s website has good information for you. Ventilation is also important to not only cool the attic but to vent water vapor as well. You don’t want either dry rot or rust! I guess the main thing with insulation is to be sure it’s done properly. If you stuff insulation deep into corners where the roof meets the attic floor, it will cause the lowest part of the roof to be colder than the rest of the roof, setting up the possible formation of an ice dam. Make liberal use of the styrofoam dams and soffit vents available. The roofer’s rule of thumb for venting is 1 square foot of vent for every 150 feet of attic floor area. Remember, a properly installed roof can eliminate much of the damage ice dams cause. So if you are starting out new or having repairs done, do it RIGHT. Don’t cut corners and save yourself lots of money and headaches later on.
Ice Dam Prevention Products
Snow Rakes: Snow rakes can be used safely to pull snow off a one-story roof. You will need to be willing to put in the time and effort to use your rake whenever snow begins to build up. A good reminder is that you only need to pull the snow away from the edge of the roof, not the entire roof! Still, be careful, though, to ensure the roof will not be harmed; the rake is lightweight but could inflict some damage!
Ice Melting Cables: Heating cables mounted on the roof are designed to form a path for melted snow to travel through an ice dam. They can work quickly, especially if laid underneath a thin sheet of metal, but you really want to have them match the rest of your roof without standing out too obviously. The nice thing about them is that you can place them along especially problematic areas. The bad thing about them is that you must remember to turn them off as they will quickly burn out if left on for an extended period of time. Whatever means you use to prevent ice dams, do it safely and efficiently to prevent lasting damage to your most expensive investment!