Results 1 to 14 of 14

Thread: Looking for advice on roof de-icing tape/cables

  1. #1
    Join Date
    Sep 2009
    Location
    Three Rivers, Central Oregon
    Posts
    2,320

    Looking for advice on roof de-icing tape/cables

    I'm planning to install deicing cables along the roof eave, valley, 4gutters, and downspout over my garage to eliminate ice damming and allow the melted water to flow down to the ground. I've looked at several brands offering self-regulating commercial quality cable and they all recommend 18" high zig-zagging along the eave and double cables in the gutter. The cable is expensive and I'm wondering if a shorter zig-zag pattern and a single gutter cable would be sufficient. We're at 4,200 feet on the east slope of the Cascades below Mt Bachelor. Freeze/thaw/freeze cycles are the culprit, particularly in the roof valley where we've had giant icicles reaching almost to the ground. Anyone using deicing cables that can offer suggestions?
    Attached Images Attached Images
    Scott Vroom

    I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.

  2. #2
    Join Date
    Feb 2008
    Location
    E TN, near Knoxville
    Posts
    11,328
    Quote Originally Posted by scott vroom View Post
    I'm planning to install deicing cables along the roof eave, valley, 4gutters, and downspout over my garage to eliminate ice damming and allow the melted water to flow down to the ground. I've looked at several brands offering self-regulating commercial quality cable and they all recommend 18" high zig-zagging along the eave and double cables in the gutter. The cable is expensive and I'm wondering if a shorter zig-zag pattern and a single gutter cable would be sufficient. We're at 4,200 feet on the east slope of the Cascades below Mt Bachelor. Freeze/thaw/freeze cycles are the culprit, particularly in the roof valley where we've had giant icicles reaching almost to the ground. Anyone using deicing cables that can offer suggestions?
    Yikes, sadly I have no suggestions for you but your post makes me glad I live in the south!! One time in 50 years we had a single icicle over 4' long at the end of an open gutter. Usually there is nothing over a few inches and even those are gone in a day.

    JKJ

  3. #3
    Join Date
    Sep 2016
    Location
    Modesto, CA, USA
    Posts
    6,527
    I think the cable has to cover the entire eaves and up several inches onto the part of the roof above the actual building. Wider eaves thus require wider zig zag.
    Just guessing here.
    Bill D.

  4. #4
    Join Date
    Sep 2007
    Location
    Longview WA
    Posts
    24,083
    Blog Entries
    1
    My understanding of this is the likely culprit may be heat escaping through your ceiling up to the roof due to lack of insulation in the attic area. The snow melts, runs down to the cold eves and refreezes causing an ice dam.

    It could also be water freezing in the down spouts causing the gutter to back up and freeze.

    It may be better to find the cause of the problem instead of trying to fix the symptom.

    jtk
    Last edited by Jim Koepke; 10-16-2021 at 6:22 PM. Reason: words, words, words
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  5. #5
    The dams usually get formed from warm air in the attic melting the snow on the roof and then it freezing when it gets to the cold overhang. This causes ice to form, which then starts to build up and create a dam, trapping more and more water, until it looks like your picture of the Winter Wizard's castle.

    The cables keep channels open so the liquid water can drain down to the gutter and downspout, which you run cables through so they stay open to allow the water to drain off the roof to the ground. You need the cables to go past where the wall meets the roof, otherwise you will just get an ice dam above the cables.

    Supposedly proper insulation and venting in the roof will prevent ice dams, but in reality sometimes they just happen. I get them on an inside northwest corner of the roof that doesn't see the sun from October until about April. Adding heat cables there fixed years of pain and suffering and slipping on ice walking out the front door.

    Looking at your picture and how your door is recessed far back, you may need to run the cables up quite high to get past where the dam forms. It is hard to tell exactly from the picture. It depends on where the "warm" part of the attic starts and the "cold" part of the eaves begins. Depending on how bad the dams are, you may need to run up a bit up the valley as well.
    Last edited by Andrew Seemann; 10-16-2021 at 6:59 PM.

  6. #6
    Join Date
    Sep 2009
    Location
    Three Rivers, Central Oregon
    Posts
    2,320
    Quote Originally Posted by Jim Koepke View Post
    My understanding of this is the likely culprit may be heat escaping through your ceiling up to the roof due to lack of insulation in the attic area. The snow melts, runs down to the cold eves and refreezes causing an ice dam.

    It could also be water freezing in the down spouts causing the gutter to back up and freeze.

    It may be better to find the cause of the problem instead of trying to fix the symptom.

    jtk
    My home is 14 years old and compliant with energy codes at the time, however there may be opportunities to add more insulation and I'll look into it. I believe a bigger problem is that the attic is poorly vented, causing warm air to become trapped. Adding a gable fan would lower the attic temp and reduce the amount of roof snow melt. It's on the to-do list for next summer.

    Adding to the above, we live at an elevation where snowstorms are often followed by periods of relatively warm mid-day temps that cause snow melt followed by overnight freezing that builds up the dams.
    Scott Vroom

    I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.

  7. #7
    Join Date
    Feb 2003
    Location
    McKean, PA
    Posts
    13,782
    Quote Originally Posted by scott vroom View Post
    My home is 14 years old and compliant with energy codes at the time, however there may be opportunities to add more insulation and I'll look into it. I believe a bigger problem is that the attic is poorly vented, causing warm air to become trapped. Adding a gable fan would lower the attic temp and reduce the amount of roof snow melt. It's on the to-do list for next summer.

    Adding to the above, we live at an elevation where snowstorms are often followed by periods of relatively warm mid-day temps that cause snow melt followed by overnight freezing that builds up the dams.
    Unfortunately building codes are the minimum standard and often don't require the best technology. Ridge vents and soffit vents are pretty inexpensive and greatly reduce the likely hood of ice dams. Installing a roof fan will do little if the soffits are not properly ventilated.

    As noted above, ice dams are caused by heat escaping through the attic insulation and warming the roof melting the snow. The water runs down the roof slope and freezes when it reaches the cold overhangs at the bottom edge of the roof. Proper attic ventilation is easily achieved by adding a ridge vent and soffit vents so that the attic space remains cold. Added insulation in the attic, insuring that there are no gaps will also help and cut down your heating costs. Heat tapes consume lots of power. An roof fan won't help much if the soffits don't let sufficient air in and may in fact pull more warm air out of your home into the attic. The lowest cost long term solution is to fix the ventilation and warm air leak problem.
    Last edited by Lee Schierer; 10-16-2021 at 7:26 PM.
    Lee Schierer
    Captain USNR(Ret)

    My advice, comments and suggestions are free, but it costs money to run the site. If you found something of value here please give a little something back by becoming a contributor! Please Contribute

  8. #8
    Join Date
    Mar 2006
    Location
    Northeast Ohio
    Posts
    521
    Heating cables are used on parts of my house, applied by me. They zig-zag on the roof probably 12-24 inches in height with lateral spacing of 8-12 inches. These are guesses as it is dark now and am unable to measure definitively. I also run a cable in the gutter channel to keep that open for water flow. We’ve done this for maybe 10 years now. This has been successful for us.

  9. #9
    Join Date
    Jul 2007
    Location
    NE OH
    Posts
    1,890
    Adding insulation and especially air sealing will help minimize the problem; air sealing the top plates and sealing any penetrations is usually the most helpful. But even with a well insulated, air sealed, and ventilated attic you can get ice damming when you have sunny days and cold nights, especially if you have a dark roof, and especially if the daytime temps get up near 32F. The sun warms the roof enough to melt some of the snow, usually on the upper part of the roof where the snow pack usually isn't as deep, and the water flows down making slush lower on the roof which then freezes overnight. Repeat a few times and you get a nice ice dam.

    The key thing with cables is to make sure they are turned on at the first sign of snow; they don't get very hot, and are much more effective if they can melt the snow around them as it falls rather than trying to thaw a solid ice block. This helps keep the ice dam from forming and growing up the roof.

    In addition to the zig zag on the roof and the cables in the troughs, it's recommended to run the cables in the downspouts as well.

    The cables work well; they do make it a pain to clean the gutters, and they are costly to run.
    --Certainty is the refuge of a small mind--

  10. #10
    In ‘11 when we were moving from MA-CA, we were closing on the sale of the house the end of Feb. For 5 wks we had a substantial snow storm/week and the accumulation was about 4’ on the roof. Everyone was loosing gutter, spouts, and ceilings due to the ice dams. I had new gutters and was afraid they would carry away. The ice was a good ft above the gutters and 2-3 up the roof. Drastic action was called for. I ran 100’ of hose from my tankless water heater up onto the roof and put a spray nozzle with a shower like pattern. I began at ground level clearing the ice from the d-spout. Oh, I had shoveled the roof off. That was fairly straightforward. I took the shovel and cut a seam up the roof as wide as the shovel itself got up on the peak and began pushingFortunately conditions were such that it let go and within a couple hrs I was on the shingles above the ice with the hose. Starting at the downspout end I cut “bread loaves” in the ice. That was enough to clear the bottom of the gutter and the water was running freely. I carefully stepped up the edge of the gutter. It was two stories up on the front and three on the back. I got the front and back done and the roof looked like a day in June. The neighbors and folks driving by thought I was nuts, but they were all over asking if I could do theirs. I ran 120* water off the tankless for about 3-4 hrs, but you can certainly melt ice with 50* water too. I saved the roof, we closed and made the move.

  11. #11
    Join Date
    Sep 2009
    Location
    Three Rivers, Central Oregon
    Posts
    2,320
    Getting back to my original post, I'm looking for input from cable users on whether a single heating cable in the gutter is sufficient in their situation. Adding a second gutter cable increases the cost substantially for the cables I'm looking at (Radiant Solutions Heat Tape Pro).
    Scott Vroom

    I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.

  12. #12
    Quote Originally Posted by scott vroom View Post
    Getting back to my original post, I'm looking for input from cable users on whether a single heating cable in the gutter is sufficient in their situation. Adding a second gutter cable increases the cost substantially for the cables I'm looking at (Radiant Solutions Heat Tape Pro).
    In my worst ice damming gutter, I had a section with one cable, the rest was double cabled. The single section had trouble staying clear and sometimes froze over. I changed the configuration of the cables the next winter so it was doubled the whole way; that did work better.

    Where I only got mild dams, I only ran a single section; that seemed to work fine there. It probably depends on how much heat your cables are putting out, and how much water needs to go through. I've just got the cheap Frost King cables. There are probably better ones out there, but these seem to work well enough.

    Keep in mind, the cost of installing and operating the cables is nothing compared to the cost of the damage that repeated ice dams can create over the years. It quite possibly is cheaper than fixing the actual cause of the problem, assuming it is even fixable in the first place.

    Unsolicited advice section. I have mine set up so a small light is on outside when they are running. Having some visible indication that they are on helps you remember to turn them off (and on). The cables only need to be on when it is snowing or when the weather is warm enough to allow melting, either from sunlight or heat escaping into the attic. If it gets down into the low teens or single digits, you typically don't need to run the cables unless the sun is melting the snow.

  13. #13
    Join Date
    Sep 2009
    Location
    Putney, Vermont
    Posts
    1,001
    I have a 32 inch overhang on my ranch style house and had ice hanging from rain gutters unti I increased the soffit size in my eaves.
    Their were small round soffit vents installed originally and I took those out and installed rectangular ones that were about 3 to 4 times bigger then the round soffit vents.
    I also opened up the insulation between the rafters in the attic enough to get good airflow up to the ridge of the roof.
    No more ice buildup now.

  14. #14
    Join Date
    Feb 2003
    Location
    McKean, PA
    Posts
    13,782
    Quote Originally Posted by michael langman View Post
    I have a 32 inch overhang on my ranch style house and had ice hanging from rain gutters unti I increased the soffit size in my eaves.
    Their were small round soffit vents installed originally and I took those out and installed rectangular ones that were about 3 to 4 times bigger then the round soffit vents.
    I also opened up the insulation between the rafters in the attic enough to get good airflow up to the ridge of the roof.
    No more ice buildup now.
    So about how much did all that cost?

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •