It's that cold time of year again -- that's right, winter! We have lots of snow, freezing temperatures, and... incredible icicles hanging off houses:
Conditions have to be just right for these icicles to form. First, you need lots of snow accumulated on roofs. Second, you need below-freezing temperatures for many days in a row. Finally, of course, you need a house that loses lots of heat through its attic/roof.
These icicles are an easy way to spot houses that waste heat, something that's otherwise not normally easy to detect! In the winter, here in New England, such houses stand out very clearly.
Of course, roof snow does also melt for legitimate reasons. For example, when the temperature outside moves above freezing, the snow will melt. However, the resulting water simply falls off the roof. It's only when ambient temperature is below freezing, yet the snow is still being melted (from waste heat leaking through the roof) that you get immense icicles. The water dribbles down the roof, under the snow, and upon hitting the roof's edge / gutter overhang, which is not wasting heat, it freezes.
Given enough snow, wasted heat, below freezing temperatures, and time, you'll get amazing icicles. I can understand that older homes will have poorer insulation and thus waste heat: standards were more lax back then, and we generally were not as environmentally conscious as we are today. But, when I see massive icicles on new construction, it's disappointing:
These icicles are very firmly attached to the roof/gutter, since Mother Nature carefully froze them there one drop at a time. However, as pretty as they are, these so-called ice dams can do massive damage. There are all sorts of products and services out there to try to make them go away. But the best solution, of course, is to simply prevent them from developing in the first place, by addressing the root cause: stop wasting heat. You can add insulation to your attic and/or turn down the thermostat.