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Old 01-28-2011, 09:28 AM
 
Location: Townsend, Massachusetts
297 posts, read 828,211 times
Reputation: 112

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Anyone have ice dam elecrtrical cables on your roof? When my electrician installed the cables he layed them out in the triangular pattern that is suggested by the manufacturer. The manufacturer also suggests to let the cable hang over the edge of the roof by about 1" (forget the exact dimension). This layout seems to create huge icicles hanging off of the roof. These icicles have come crashing down and damaged my vinyl siding and the aluminum wrapping around my basement windows. Any ideas to curb this. Are the cables installed correctly? I tried pushing the icicles off and ended up damaging my siding because the icicles seem to rotate as they fall. I should mention that the home is approximately 2 1/2 stories high. Thanks in advance all.
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Old 01-28-2011, 01:49 PM
 
Location: Somewhere in northern Alabama
18,760 posts, read 55,897,290 times
Reputation: 33052
The cables are installed correctly. We used to have them when I lived in Vermont. Icicles do form on them under certain conditions, especially if you wait to turn the power on until there is a buildup of snow. Usually, the simple answer is to keep them on all the time.
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Old 01-28-2011, 02:01 PM
 
Location: Johns Creek, GA
13,162 posts, read 50,627,040 times
Reputation: 15370
It sounds as if you have no gutters. And, once the water get far enough away from the heat cables it refreezes- repeat this process over and over and icicles you have.
Heating cables are the least evasive "solution" that should be used in eliminating ice dams/icicles.

Assuming a vented roof, you should build or retrofit a well-insulated attic or cathedral ceiling to keep attic air and roof surface cold to prevent warm spots on the roof which can lead to snow melting. This usually occurs directly above the exterior walls because of the roof framing not allowing enough space to use the correct thickness of insulation. Or, a combination of that and no soffit vents, and/or blocked soffit vents. Sometimes, there are no baffles in the attic for air flow or in vaulted ceilings.
A well-sealed ceiling air barrier (like those insulated caps for pulldown stairs- along with weatherstripping of the door itself) to prevent warm air from leaking into the attic.
A ventilated attic or cathedral ceiling to keep the inside face of the sheathing cold in winter. Using a waterproof membrane under the roofing or at least the first three/four feet. This will not prevent damming, but will inhibit water from backing up under the shingles and into the roof structure and living space below.
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Old 01-28-2011, 02:14 PM
 
Location: Townsend, Massachusetts
297 posts, read 828,211 times
Reputation: 112
The roof has a ridge vent and two gable vents. There are no soffit vents. The roof is 2 years old. There is a weatherproof membrane 3 feet above the roof edge. I think I am ok with the ice dam situation but was wondering how to keep from getting the icicles. Harry suggests keeping the cables on all the time. I guess I was just concerned with electricity usage, that is why I didn't leave them on all the time.
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Old 01-31-2011, 06:07 AM
 
Location: Townsend, Massachusetts
297 posts, read 828,211 times
Reputation: 112
Anyone have any ideas as to how much $$$ it would be to leave the cables on constantly???
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Old 01-31-2011, 07:11 AM
 
Location: Johns Creek, GA
13,162 posts, read 50,627,040 times
Reputation: 15370
Quote:
Originally Posted by brrrinmass View Post
Anyone have any ideas as to how much $$$ it would be to leave the cables on constantly???
That will depend on your rate-
But, I'm sure it would be high. I'm a betting man and say those things are pulling some pretty good amperage (use of an amp meter will confirm)- do the math.
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Old 01-31-2011, 12:19 PM
 
Location: Somewhere in northern Alabama
18,760 posts, read 55,897,290 times
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Five watts per linear foot is about average. That means 200 feet would be 1,000 watts. If the electric rate per KWH is 12 cents, that would be worst case about $90/ per month of continuous use. In most localities, there are weeks in winter where there is no snow on roofs, and during those periods the cable could safely be powered off, probably cutting costs in half. The key is - once there IS snow on the roof, power the cable on and leave it on until the snow is gone.

If the job was done correctly, a sensor was installed that should properly regulate when the unit comes on and goes off. That means leaving it on all the time might cost even less.

Heat cables are an active method of handling the icing problem. Installation is quick and relatively inexpensive. The trade-off is that they cost money to operate and can be subject to damage (being pulled from the roof by falling ice) if not operated properly.

Other methods of dealing with the issue cost more initially. Obviously, insulating the attic and keeping attic and soffits as close to air temps as possible is a good thing. Many older houses have a wide metal band exposed at the edge of the roof - and NO gutter. Areas over entrances to the house have dormers or gable ends, so that no ice (or rain) can sheet off the roof onto someone. Some folks shovel or otherwise remove snow from their roofs before it can become a problem.

If a house is historic or zoning is strict, sometimes you just have to deal with the idiosyncrasies and pay for them. Repair of a rotted roof deck and water dripping down walls and ceilings is a lot more expensive than a couple hundred dollars a winter.
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Old 02-02-2011, 06:47 PM
 
Location: Townsend, Massachusetts
297 posts, read 828,211 times
Reputation: 112
Quote:
Originally Posted by harry chickpea View Post
Five watts per linear foot is about average. That means 200 feet would be 1,000 watts. If the electric rate per KWH is 12 cents, that would be worst case about $90/ per month of continuous use. In most localities, there are weeks in winter where there is no snow on roofs, and during those periods the cable could safely be powered off, probably cutting costs in half. The key is - once there IS snow on the roof, power the cable on and leave it on until the snow is gone.

If the job was done correctly, a sensor was installed that should properly regulate when the unit comes on and goes off. That means leaving it on all the time might cost even less.

Heat cables are an active method of handling the icing problem. Installation is quick and relatively inexpensive. The trade-off is that they cost money to operate and can be subject to damage (being pulled from the roof by falling ice) if not operated properly.

Other methods of dealing with the issue cost more initially. Obviously, insulating the attic and keeping attic and soffits as close to air temps as possible is a good thing. Many older houses have a wide metal band exposed at the edge of the roof - and NO gutter. Areas over entrances to the house have dormers or gable ends, so that no ice (or rain) can sheet off the roof onto someone. Some folks shovel or otherwise remove snow from their roofs before it can become a problem.

If a house is historic or zoning is strict, sometimes you just have to deal with the idiosyncrasies and pay for them. Repair of a rotted roof deck and water dripping down walls and ceilings is a lot more expensive than a couple hundred dollars a winter.
Thanks for the info. We just recieved another foot of snow over the last 2 days. Winter in New England. Guess the cables will be on a little while longer. The house is 2 and a half stories in the back and the icicles are 2/3 of the way to the ground and about 9 inches around on the top. I am starting to worry they will tear off the aluminum wrap around the facia. I can't wait ti move to AZ.........
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Old 02-02-2011, 10:36 PM
 
Location: Somewhere in northern Alabama
18,760 posts, read 55,897,290 times
Reputation: 33052
That is getting excessive. If you know of someone with an inground pool, see if you can borrow the extendable aluminum wand that is used with a skimmer basket. That should be long enough that you can safely knock a few of the bigger puppies down. Otherwise, 2 10' lengths of metal conduit and a connector should get you enough height. Check with a home store. Just be sure to clear or pack an escape path.
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Old 02-02-2011, 11:14 PM
 
40,829 posts, read 42,222,749 times
Reputation: 17093
Quote:
Originally Posted by brrrinmass View Post
Anyone have any ideas as to how much $$$ it would be to leave the cables on constantly???

((Appliance wattage * Hours of operation ) / 1000) * Price per kWh = Cost


A quick search says about 8 watts per foot but I'm guessing there is many different wattages and I'm assuming that is cable length and not roof length since you need to install them in triangle pattern.

Just guessing here but 200 foot of cable to do 100 foot of roof? At 8 watts per foot you have 1,600 watts, assuming you ran it constantly for 30 days and 11 cents per kWh:


((1600 * 720 ) / 1000) * .11 = $126.72
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