I have written extensively on the subject of ice, snow, and metal roofs. To find that information, just Google for Ice dams, metal roofing, and Todd Miller. However, I want to share that I feel that the potential benefits of metal roofing in terms of helping roofs resist ice dams are often over sold.
What typically happens with a metal roof after a snowfall is that, when the sun comes out, radiant heat from the sun passes through the snow on the roof and reflects back outward. This will cause the snow to slide off the roof, much like snow slides off of the hood of a car once the engine warms up. In fact, some homeowners will choose to have snow guards or snow fences put on their roofs to slow down the sliding of the snow or at least cause it to slide in small chunks, in order to protect doorways or plantings and statuary which may be located around their home. However, if snow accumulates on the roof, and the sun does not come out, then heat that escapes from inside the home can cause the snow to melt and then, if it re-freezes on the home’s unheated overhangs, ice dams will form, the same as they will on any roofing material. Ice melting systems can be installed with or on the roof if your home is prone to this.
Sometimes roof geometry plays a role, too. Some roofs, simply by their design and shape, do not encourage snow to slide. If the snow never slides, then there is a greater chance of ice dams occurring. In summary, metal roofing does offer good protection from ice and snow but it is not necessarily the end all and be all. If you wish, reach out to us about your ice and snow issues and we can discuss options which may work for you.