Here is another solution. I take all my rigged eels which have been soaking in brine solution for years and place them on the ice dams. They slowly emit brine solution and keep my gutters free of ice. As long as it's cold the eels stay fresh - just don't leave them on your roof in the spring time. :)

DZ

I honestly don't know about what happens when the first solid water and solid CaCl2 meet. What you need to think of is all the CaCl2 he had to add to just 50 CC of water to get a 25 degree rise. All that saly would have melted 100 times more water do to the lowering of the freezing point where as that much heat 50 CC X 25 degree rise at 1 cal per degree =1250 cal. That isn't much heat when you think of all the area of snow , the weight of the ice , the latent heat of fusion of the water which is 80 cal /gram (1gram of water is 1 CC) . The exothermic heat is just such a drop in the bucket that its effect in melting real ice amounts on a roof or road , etc is negligible. I will give you that there may be some roll of the heat of reaction in initiallizing the process as I'm just not at all sure but my gut reaction is that even that is not true or if true again almost insignificant beyond just getting the first few molecules of water to go liquid.

But anyway , I think we all now have enough Physical Chemistry knowledge of the salt/water reactions and Phase equilibrium to last us a lifetime. :)

DZ- THAT IS CLASSIC:rotf2::rotf2::rotf2::rotf2:

The one point of the building science thing that I posted is that the reason you get icedams is you are losing heat thru the roof. If you do the things they suggest you will 1. Not have ice dams 2. Save money on fuel. Sometimes the cure can be done in less time than it takes to chop off ice dams. Most airsealing and insulation upgrades are pretty low tech.

where would we be without PRBUZZ to straighten us out on all things involving chemistry and hot babes?

The most important point of all. I had cracks running up the corners of four closets that I finally patched this year. That warm air getting out of the rooms and in to the wall interiors goes straight up to the attic. I also taped over all the unused wall sockets. Add this to the attic insulation I've done in the last couple years and I've got more snow on my roof than any neighbor - because my attic is so cold. I did get ice in my gutters, but none on the roof itself, and no water leaks.