"Walter Cohen" wrote:

I live in NY state and had roof ice dam damage in a past year. Ever since
then I've had additional under-eave ventilation vents put in and try to keep
parts of my roof clean (to some degree) of winter snow using a long handled
shovel.

Removing snow buildup is only needed if you have a roof with
uncorrected problems. One permanent solution is a 2 to 3 foot wide
metal flashing leading up from the eave edge. The roof melt can
freeze on it and yet do no damage. Another solution is resistance
wire in a zig-zag pattern along the same area. In many houses,
increasing the attic insulation is all that is needed.

Under-eave vents may or may not work. The problem usually occurs from
snow melt on a dark unvented roof or one that has insufficient attic
insulation to keep it cool. A ridge vent or turbines will do a better
job of keeping it cool. Once the melt hit the area over the eaves, it
is colder, so the melt forms ice. Cooling the eaves by adding vents
does little to help, and can even make the problem worse.

Another simple solution can be 3' lengths of 1/2" black painted copper
pipe that are spaced avery 3 feet and extend out about a foot over the
edge. The sun heats the exposed pipe, and the slight temperature
differential melts a channel for runoff. A black copper fin at the
end of the pipe can increase the solar heating.