Heat Tape

Heat Tape   

Roof heat tape or heat cables whichever you prefer to call them, can be a benefit to your home for sure. The basic purpose for heat tape is to reduce or eliminate ice dam backups on the house at the unheated eave edges. To keep water outside your home in the winter, not inside! BUT, the only way heat tape can be a benefit is if it is installed correctly!

heat tape

This heat tape installation gets a “D.” This could actually help create an ice dam!


“so how does an ice dam evolve from “snow” 





  • It snows and there is a nice thick white blanket of snow on the roof
  • As the snow lays there on the roofing shingles over a period of time, the layer of snow that is closest to the roofing shingles begins to melt due to heat loss through the attic
  • Melting snow water runs down the roof under this top blanket of snow and hits the eave area just past the exterior wall of your home. You do not see this happening because of the top layer of snow is hiding this sneaky little activity

NOTE; Remember under the roof is your attic and inside the attic there is insulation (or should be) that lays on top of the ceiling. Hopefully you have the proper amount of insulation so check this energy star national map out to see what you should have based on your area. Next, under the insulation is the top of the sheet rock ceiling and on the underside of this sheet rock ceiling are the heated rooms in the house. This is the heat that is lost in your house that travels up, hits your ceiling, absorbs through the ceiling, goes through the insulation (maybe because there is not enough) and hits the underside of your roofing wood deck. This lost heat is what you have melting the snow and now have snow water running down under the snow blanket. (Can you visualize this yet?)

  • So continuing this evolution. This melting snow water hits the eave area and freezes because there is no heat outside your exterior wall line to keep it liquid and running down. So this moving water stops because it starts to re-freeze at this point and forms (we will call it) a little ice wall, hump or more properly, an ice dam
  • As this melting snow water continues to run down and hits this little ice dam and attempts to run over this little ice dam, it can’t because it immediately freezes
  • And so, this perpetual action continues. More snow water runs down and freezes when it attempts to run over the ice dam, and more snow water runs down…you get the little river picture in your head I hope
  • Now this little ice dam starts to build in height…maybe 2″ or 3″ or 8″ inches high.  This means that zero water is draining off the roof now
  • So water starts building up behind the ice dam, puddling behind this growing ice dam and now the ice dam has created a water levee go look at an example here.  So now water is able to pond behind this ice dam and when you have ponding water on a roof, this water is going to find the path of least resistance. Guess what? It’s trying to invade your home and cause water damage, mold, rot and other disgusting things
  • Now this ponding water that is being fed from the stream of melting snow water behind it is backing up and getting larger and moving backwards up and under the roofing shingles.
  • Once the snow water gets to this point, trouble is just minutes or hours away. This backed up water finds any break in the seam of felt paper, nail holes, rip or tear in the felt paper, etc. the water is going to leak into your attic, through the insulation and onto the ceiling sheet rock. Eventually the water will find a point that it starts to puddle and soon, start dripping (or running) down your wall, windows, through the ceiling or a light fixture

“Take a look at a picture of major ice dam”

heat tape

Properly installed heat tape! Notice that because of the heat generated from the tape/cable at the eave, no ice is building up!

  •  Roofing heat tape or heat cables installed properly can reduce ice dams or even keep them from ever building up. (You must read the installation guide that comes with the heat tape! It should tell you to never overlap or have the heat cables cross over each other and important things like that.)
  • These heat cables are being energized by being plugged into an electrical source. Like an outside wall outlet. Ideally, your heat tape should be plugged into a GFCI type outlet to protect you from electric shock as you are dealing with electric, outside and wet elements.
  • Depending on how many feet of heat tape you need on your home will dictate the amount of circuit energy it will be using. You don’t want to hook your new system up only to trip your breaker in your main electrical panel. This trip of the breaker could happen when you are away from home and if this outlet energizes more than this heat tape, what else just got shut off, your refrigerator? Another suggestion is to have an outside weatherproof outlet box setup like this one, for example.

You may wish to have an electrician evaluate your wiring output and install this for you

Most all roof tape or roof cables have some sort of a built in temperature controller switch. You do not want your heat tape turned on say, when it’s above 35 for obvious reasons. “Lets be a little green here.” The heat tape is also typically converted down to low voltage (or should be.) It might be a good idea to have someone who has installed heat tape before to give you some pointers.

So lets examine what this heat tape installation might require material-wise to install.   

Please click here to go look at an example picture of a finished heat tape installation. And also note the cable in the gutter… IMPORTANT NOTE, you will need much more heat tape that you think you need IF you do not measure everything correctly. You should start by dropping the plug in end of the heat tape down the gutter downspout and pull cable over to the outlet so you can plug this in at ground level. You are also going to want to run your heat tape inside your gutters as well. (You want to be sure the ice dam you are turning to liquid water can get all the way to the ground before freezing again.) Now, measure from the eave edge (assuming it’s a 2′ foot eave) and go 3′ feet up past the outside wall line up the roof, so a total of 5′ feet up at a slight angle then back down. Have about a 10″ inch wide gap at the bottom between the cables. (look at picture again) When you are done, the entire eave area should look like an upside down had wood-saw tooth blade. Use the supplied heat tape or cable clips supplied. You will probably need more so be sure to order more shingle clips. When you’re done with the installation, the pattern should like a giant upside down “V” pattern.

 Hope this helps you with your understanding of ice dams, heat tape and the electrical needed to properly keep these monsters from invading your home. For your convenience, you can shop here to get everything you need.