# Ice damns and roof de icing cables



## Pak713

Hello everyone. New member here and I'm from Michigan. Our house is a 1.5 story house. The rooms in the upstairs are attic rooms or rooms with knee walls. I re insulated our attic last year and it helped quite a bit on keeping the upstairs warmer in the winter. On one particular side of my house I have really bad ice damns. I know that my attic and roof on that side isn't ventilated very good. Our first good snowfall came pretty early to me. I meant to do a lot of stuff before that got here but didn't get the chance to. Anyway I bought a roof de icing cable to try and help with the ice damning problem until spring gets here to try and fix the issue for good. My gutters are completely frozen and I now have ice damns up as far as I could reach with my roof rake. Probably about 6-8 foot up the roof from the gutters. Well I didn't realize that the roof de icing cable recommends not using an extension cord until I got home. My question is I have a big heavy duty 100ft 12/3 extension cord and I was wanting to know if that would be sufficient enough to run the cable for a few hours a day or not. The cord would be plugged into a protected strip in my garage. This is my only option as of right now. I didn't think this would be an issue but at the same time don't really know for sure. The protected outlet is on a 15 amp breaker.


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## nealtw

I would use it. Be sure to come back and talk about the venting.


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## VanMark

Those heating cables are generally only good when weather is just around freezing 32 degrees.Wont help much if temperature falls below that.


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## kok328

Plug it in FWIW.


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## Pak713

So I did end using the de icing cable. It worked fine. Although I wasn't able to correctly install the cable due to the amount of ice. So as soon as the ice is gone I will be installing it correctly. We are having a warm spell currently so the ice is almost completely gone. So I have a few more questions and I was hoping someone could help me out. So as I currently mentioned my house is a 1.5 story house. The bedrooms up stairs have knee walls. Above the bedrooms there is a small attic space as well. So I have been working on sealing up the gaps between the knee walls and the floor joists. I was able to completely do one side of the walls. When I originally started the knee wall attic space that I can access from the other main attic was noticeably warmer. After sealing all the gaps between the floor joists it seem to be the same temperature as the other attic. The other knee wall attic I can't access. I plan on cutting access doors in the upsatairs bedrooms to access the attic space and seal up all the gaps. The problem I'm still wondering about is my knee walls are insulated from the beginning of the wall straight up the rafters and up to the small attic space above the bedrooms. I have soffit vents and box style roof or ridge vents. The small attic space above the bedrooms are noticeably warmer than the rest of the attic space. Maybe because it's so small? Will the insulation that is running up the sloped part of the ceiling hinder air flow? Most of the pictures or diagrams I've found on the internet show just the knee wall and the flat part of ceiling being insulated, not the sloped part of the ceiling. I kinda of feel like maybe the air flow isn't flowing like it should. Also why is the attic above the bedrooms so warm?? Sorry for the long post, but I really don't have anyone to ask about this. Hopefully I've explained everything well.


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## nealtw

Pak713 said:


> So I did end using the de icing cable. It worked fine. Although I wasn't able to correctly install the cable due to the amount of ice. So as soon as the ice is gone I will be installing it correctly. We are having a warm spell currently so the ice is almost completely gone. So I have a few more questions and I was hoping someone could help me out. So as I currently mentioned my house is a 1.5 story house. The bedrooms up stairs have knee walls. Above the bedrooms there is a small attic space as well. So I have been working on sealing up the gaps between the knee walls and the floor joists. I was able to completely do one side of the walls. When I originally started the knee wall attic space that I can access from the other main attic was noticeably warmer. After sealing all the gaps between the floor joists it seem to be the same temperature as the other attic. The other knee wall attic I can't access. I plan on cutting access doors in the upsatairs bedrooms to access the attic space and seal up all the gaps. The problem I'm still wondering about is my knee walls are insulated from the beginning of the wall straight up the rafters and up to the small attic space above the bedrooms. I have soffit vents and box style roof or ridge vents. The small attic space above the bedrooms are noticeably warmer than the rest of the attic space. Maybe because it's so small? Will the insulation that is running up the sloped part of the ceiling hinder air flow? Most of the pictures or diagrams I've found on the internet show just the knee wall and the flat part of ceiling being insulated, not the sloped part of the ceiling. I kinda of feel like maybe the air flow isn't flowing like it should. Also why is the attic above the bedrooms so warm?? Sorry for the long post, but I really don't have anyone to ask about this. Hopefully I've explained everything well.



solid blocking between the joists below the knee wall should be there to isolate the attic space behind the knee wall, then you want the insulation on that attic floor and the knee wall and up the slope but you do need air space above the sloped section insulation.
In new houses, the rafters are made out of 2 x 10s to allow for air and insulation.
The real fix you need is to make the rafters deeper.
If you can dig some of the insulation from the sloped area to make air flow you might just add more insulation to the lower side of the slope and more drywall.


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