Roof heating cables

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Old 02-10-17, 07:06 AM
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Roof heating cables

Hi. We moved into our house a few years ago and the prior owner had installed something like this:

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I've used it on occasion when it's snowed over the years, but have never bothered to ask anyone the exact, proper way/timing to use it.

As an aside, I'm not sure it works all that well, or perhaps the gutter guards that he also installed are interfering with it, because often times even if the roof edge looks pretty clear, the gutters are still full of snow/icicles form.

In any case, what is the proper timing of using the heater? Do I turn it on as snow starts, and turn it off when snow stops? Or do I leave it on longer to avoid anything that has melted from refreezing (especially if it's below freezing for a while after the snow stops)?

Thanks!
 

Last edited by PJmax; 02-10-17 at 11:45 AM. Reason: added pic from link
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Old 02-10-17, 07:20 AM
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Turn them on when it begins snowing. It's safest to leave them on until all the snow is gone from the roof. This ensures any snow melt from the sun or warm attic air will not freeze in the gutters and downspouts, assuming the installation was done properly and the cables also run through the gutters themselves and down the downspouts.

Not a big fan of roof deice cables as they are an expensive solution (expensive to operate) to a problem that is better dealt with by improving attic air sealing, insulation, and ventilation. However they are better than allowing ice dams to form and in some problem roofs can be an effective solution.
 
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Old 02-10-17, 07:31 AM
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Hi 0101, ice and related ice dams occur in a narrow window of outside temperatures. It has to be warm enough that the heat from inside the attic can melt the bottom layer of snow while it is being insulated by the amount of snow on the roof. In my area I have found the 25 to 30 range to be the highest risk for forming ice. Colder temps and you get no melting while warmer temps (above 32) the melted water can drip off the edge without freezing.

The heat wire approach you have is not always effective as ice dams can still form above the heated area. Those wires also make it difficult to clear the snow which can sometimes be required due to weight. In CT that may not be as bad an issue as Maine. Note we are expecting another 2'.

The real solution is air sealing and insulation in the attic and lots of threads on that topic if you need. For operating times, I would suggest any time the temps are below freezing. But check the mfg's recommendations.

Bud
 
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Old 02-10-17, 11:48 AM
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I have snow melt cables and don't always use them. I also have them inside the gutter.
The cables in the gutter and the downspouts are actually handier.

I usually use them with a heavy snow and sustained cold.
 
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Old 03-15-17, 01:46 PM
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Hi all. I wanted to follow-up this post to mention that, in certain spots I have what are basically sheets of snow/ice starting to form (coming out about 4 inches). We had a lot of snow in CT yesterday (though there's not all that much on the roof as a lot of it blew off.

I believe (I'm just guessing) that the gutter guards (which are kind of like foam/mesh inserts I believe) are perhaps hindering the snows ability to melt, or maybe causing the snow to slide off the edge (but not fall, just kind of hanging over).

Any thoughts on whether this could be the case, and is it a bad thing? It should go away in a couple days once it warms up a bit (still well below freezing here in CT).

I have good attic insulation, and it's well below freezing today, so I'm not sure why anything would be melting out over the gutter like it is, and can only assume it's the gutter guard causing this weird issue.

One of my neighbors has a very old house with most likely very bad insulation, and she already has major icicles forming. I don't have icicles, just these sheets sticking out a few inches in a few spots.

Also, I did not use the heat cables.

Thanks for any thoughts.
 
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