Can Metal Roofing Prevent Ice Dams?
Residential metal roofing salesmen often promote that metal roofing products are a great way to prevent ice dams. They toute metal's ability to let the snow slide right off. The logic is 'no snow, no ice dams'. This logic is correct. If there is no snow left on the roof, there is nothing to melt, and nothing to refreeze at the eaves. "Great" you say, sign me up.
What about valleys and ice dams with metal roofs?
This is where the problem lies. Many homes are not just a simple two straight sides at a pitch sufficient to shed the 
snow. Some homes are ranch style (lower sloped roofs) that do not typically shed snow easily even with a metal roof. Somes homes have dormers, valleys, and other architectural features that do not allow for easy shedding of snow. Sometimes these features can make the problem worse. When snow slides into a valley, it is compressed. This can make the ice dams even worse than if a conventional asphalt shingle were used. This is the single biggest reason why homeowners contact Wisconsin Ice Dam Solutions with metal roof and ice dam problems. When valleys and other problem areas exist on a home, it is imperative that the proper underlayments be used to prevent water leaking in from ice dams. Or, plan for a roof ice melt system to be used.
The picture to the right is instructive on several levels. 1) The metal roof has allowed the snow to slide into the valley where it compacts and forms an ice dam that results in leaking into the home and icicle formation. 2) The metal roof allows for unrestrained cascading of snow and ice onto the surface below. This is fine when it is the backyard. Not so good when it is over the driveway, front entry or a walkway. This snow can also cascade down onto decks or lower roofs creating structural problems. Gutters are routinely torn from homes as well when the snow cascades off the roof. To prevent snow from cascading off of a metal roof, snow stops or snow guards must by used. 3) While it is difficult to see, there is a hardware store style heat tape embedded in the icicle seen hanging from the valley area. Zig zag heat tape is not powerful enough to keep up with this type of snow fall and cascading problems.
Is metal roofing a good solution to ice dam problems?
Typically, we experience ice dams on our roofs because of heat loss, solar gain, or temperature fluctuations creating conditions where snow is melted on the roof and refreezes in the gutters or at the roof edge. Metal roofing is sometimes sold as the smart alternative to heat tape. If your home is difficult to insulate well and you are unable to stop the movement of conditioned air from the living space into the attic space, then metal roofing may not be a great choice. The reason for that is the dynamic of radiational cooling. This phenomenon is where whatever is facing the night sky cools very rapidly. In the winter, a bare roof (one that sheds its snow with cascading like a metal roof) will allow for rapid cooling that can sap heat from your home driving up heating costs and making your living space less comfortable. So, is an expensive fix that drives up heating costs a good investment? This may not be an issue if you have a well insulated attic space. You can make that decision. There are many good reasons to choose a metal roof - aesthetics, longevity, and snow load considerations. But, if you are experiencing ice dam problems, a metal roof may not always be the best choice.
There are products on the market that can extend the life of your existing roof and prevent ice dams. True, they do use energy to do so. But, our systems are among the most energy efficient ice dam prevention systems on the market today. Would you like to know more? Please get in touch with our ice dam prevention experts.
Update 3/18/13: In response to some feedback from a great metal roofing contractor I know well, I would like to let everyone know the difference between the 'salesman' style approach to metal roofing and the straight forward approach used by many metal roofing contractors. There are contractors that promise that metal roofing will do all sorts of things in order to make a sale. There are, thankfully, others that honestly represent their products and install them with integrity. It is in response to the first that the article is written.