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Updated: Jan 18

Here in Montana, winter creates ice dams on roofs and freezes rain gutter. Many people have experienced leaks into their homes due to the accumulation of ice and snow at the edge of the roof and in roof valleys.

After the ice is removed, installation of a deicing or heat cable on the roof and in the rain gutter and downspout will prevent the return of the ice. The heat cable must run through the rain gutter and downspout allowing the heated water to discharge on the ground (preferably away from sidewalks).

If the roof had ice dams that caused water damage inside the attic or home, then you should also serpentine the heat cable on the edge of the roof. Otherwise in some cases you only need the heat tape in the rain gutter & downspout.

To determine how far up from the edge of the roof you should install the cable, imagine a line drawn straight up from the outside wall and through the roof. Be sure the cable extends past this imaginary line.

There are two styles of heat cable, self-regulating & non regulating. Here in Bozeman, MT. Dovetail installs the self-regulating cable. This cable is available for 120 volts or 240 volts. The cable is purchased on 1000-foot-long spools and is cut to length. It is more expensive than what you can purchase at the local hardware store, but we feel it's a safer and more efficient heat cable. The cable regulates its heat output depending on the ambient temperature around the cable. Due to its self-regulating feature the cable can overlap itself & be safely spliced.

The non-regulating heat cable is less expensive to purchase. And sold in local hardware stores in different lengths, you need to carefully calculate the correct length to avoid having excess cable that ends up coiled against itself or is too short. It always produces the same heat and manufacturers warn that it could burnout if it overlaps itself or is covered by leaves.

Depending on the length of the cable you install and how many amps it draws you may be able to plug into an existing electrical outlet. Some installations will require a dedicated electrical supply.

Both styles of heat cable can be installed on a thermostat that will turn on the cable between a set point of around 20 - 40 degrees. Additionally, a sensor can be placed into the gutter, if there is no moisture present the heat cable won’t turn on.

1 Comment

good info here, hope we don’t have any ice dam problems this year!

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