So Hurricane Sandy decided to throw a 80' oak tree onto my roof. The whole roof had to be replaced, $29,000 and as all roofers told me, "you won't need that heat tape anymore" and he explained how the roof is all insulated now, and the roof vent, and the bla, bla, bla...
Well here is my roof this very cold and snowy season because I believed him:
I will give the roofer credit though, none of the water got into the roof, he did give me a waterproof roof.
Look I know a better insulated roof will not have the problem as bad as a poorly insulated roof, but the sun will still melt the snow, and the water will still run on the roof to the gutters, and the gutter in the shade (north/west) side of the house (where the video is showing,) will freeze even though the south/east side of the house will not dam up. So this spring, I'm putting my heat tape back up.
I put it up about 10 years ago and haven't touched it since.
I ran one 60 foot length of tape inside the gutter so water in the cutter can pour off. I use another 80 foot length for the roof. I ignored the directions. I just put the tape in upside down V's along the roof edge with the peak being about 8 shingles from the edge (that was enough so that the "peak" of the upside down "V" was about 6 inches past the vertical line of the soffet,) using the clips that came with the kit to hold it down. I'm guessing around 3 "V"'s every 10 feet. I then attached the bottom loops of the upside down V to the outer edge of the gutter.
I had to also replace the outdoor flood light that was closest to the gutter with one that had a 2 gang outdoor socket and a flood light so I could plug in the heat tape as the directions indicated. I simply unplug the de-icing cable in the off-season; the cable stays on the roof year round.
edit january 2011:
@polishdickhead I saw 80ft ones at the home depot just the other day. Here are some stills of how I did my roof:
My wife forgot to turn it on last week after the snow. when I finally saw it I could see the icicles coming out of the soffet vents (water was into the soffet already, but not in the house) I turned on the tape for 20 hours, the water poured off the roof, and the icicles in the soffett vents disapppeared.
Here is some more stills of this past winter: Note how well the heat tape drilled right through the ice. It actually made the snow into a dome where the roof was completely dry under a canopy of snow: