What about roof mounted heating cables?
Heating cables mounted on the roof are
designed to form a path for melted snow to travel through the ice dam.
The will not work if ice dams form above the heating element.
The downside is that you must cycle them on-and-off, or they will
quickly burn out. Not to mention the Electric Energy Required.
Homes do not have electrical outlets located neat the houses roof-line
to service the electrical needs of the heating cables.
Whether you do the job yourself or have an
electrician do it. Be sure to put a shut-off system that controls all
the cables at once. And the circuit is protected with a ground fault
circuit interrupter.
Properly insulated and ventilated attic is still the best
solution, because it is an ENERGY FREE Solution! So weigh the
comparative costs of each solution before choosing one... | 
