Photo Credit: zenera
Icicles on the eaves and snow on the roof are more than just an ornament of wintertime. They can also be instructive signs that you can use to get a sense of the way your house is using energy and a way to tell whether or not there are problems that you should address to improve your energy efficiency and perhaps even to preserve your roof structure.
With the recent snow that much of the midwest and northeast US has had in the past week, now can be a good time to take a look at your roof to see how well your house is doing in terms of energy performance. An article from Home Energy Magazine gives a good set of guidelines about reading the snow on your roof to see how well your attic insulation is working.
Don't just look at your roof once, and decide everything is okay, though. With freshly fallen snow, it's likely that everyone has a good blanket of snow on the roof. Photo Credit: Don Hynek, HomeEnergy.orgWhat will be telling is how quickly it melts over the next few days, and the patterns that show up. Local comparisons can also be informative. In addition to looking at your own roof, look at the neighboring houses and see what the snow patterns on them are showing. If your roof has more snow on it than your neighbor's does, it is likely that you have a better insulated attic. But if everyone else's house has a nice cap of snow on it, and your house is a display for roof shingles, then you need to get up in that attic and get some additional insulation up there.
Extensive icicles can also be a sign that your attic is insufficiently insulated and you are wasting heat. Even more, icicles can be an indicator of ice dams forming on the roof, which can cause damage to the roof and exterior walls of the house. "An ice dam is a ridge of ice that forms at the edge of a roof and prevents melting snow from draining off the roof. Because the water has no place to go, it backs up behind this ridge of ice and can leak into the home. These leaks can damage walls, ceilings, insulation and other areas."
Factors like the orientation (a south facing roof will clear faster than one that is oriented to the north), weather (a bright, sunny day can melt off the snow, especially from south facing roofs), and local environment (surrounding trees, local wind, etc.) can all contribute to how the snow sits on the roof. This is not a foolproof method, and these other factors can influence what you see.
If you are getting energy aware, this can be an easy first step in figuring out how well your house is performing. If you want to go a bit further, the US Department of Energy has a Do It Yourself Home Energy Audit that offers a few more ways for examining your home and finding other steps you can take to further improve your home energy efficiency.