Roof heat tapes are an insulated wire that warms when plugged into an electric outlet and can prevent ice dams. They are similar to an exterior extension cord except they are usually gray in color and do not have a female plug at one end. They are available in lengths from 20 to 140-feet. Ice dams
Some models do not have a thermostat so they heat continuously once plugged in. They should only be plugged in when ice and snow damage is expected. These units are adequate for homes where people are around to monitor the status of snow and ice on the building.
Other models are self-regulating so they only heat when temperatures go below a certain level. These are good for commercial installations or residences where the roof is out of sight and no one will be able to check ice and snow conditions.
To eliminate ice dams on your low pitch roof, you may need to run the heat tape from the gutter most of the way up the roof. This situation could take quite a bit of heat tape to work properly. You will not want the spaces between the wires to be too far apart or there could be mini ice dams forming between them.
Even though I sell roof heat tapes, I try not to recommend them. I would prefer people to insulate and ventilate their attics to prevent ice dams. Do not work on the problem, but work on the cause.
Ice dams form when heat from both the sun and the attic-melt snow during the day. Then the snow/slush slides down the roof until it hits the overhang and gutter. Since there is no additional heat from the house, the slush freezes, usually at night. Several warm days, cold nights, and enough heat from the house causes a monster ice dam to form.
The real problem occurs when a warm front moves in, and snow up on the roof melts. The water cannot get over or under the ice dam and backs up under the shingles. Or the point of entry through the roof is usually right over the exterior wall. Many people experience water ‘raining’ right in the middle of their windows or in the soffits in the kitchen.
You can prevent this from happening by ventilating the overhang and the roof so warm air can rise to bring in fresh cold air. This will help keep the roof cold so the snow will be less apt to melt. Then add insulation to the attic to trap warm air in the room below. I consider twelve inches of insulation to be the minimum for an attic in Michigan.
Some attics are inaccessible or have too low a pitch making ventilation and re-insulating impossible. These should install roof heat tapes. Everyone else should pay more now for the venting and insulation and reap the savings in heat bills for years to come.
Here are a few heat tape facts:
An 80-footer will draw as much electricity as four 100-watt light bulbs.
A house with a twelve-inch overhang will need a heat tape about four times the length of roof.