In article
woodchucker writes:
On 1/30/2014 10:01 AM, wrote:

I would not think that a properly vented roof would ice dam.

Ok, you get to believe what you want.

I know that even a well insulated attic , well ventilated will still damn.

The problem is the sun and air, it will melt the snow, and that will
refreeze at night if cold enough (usually is). Then the rethaw will
start the process over.... And that is where the problem occurs.

The problem that bit me several years ago was not caused by the
roof. It was caused by the gutters.

When there is snow followed by subfreezing temps, the sun melts the
snow, which drains into the gutters, where it freezes immediately.

Usually this isn't too much of a problem. But a few years back,
things combined just wrong. We'd had enough of that cycle to
completely fill the gutters. Then we got more snow, then the snow
melted from all but the eves. Then we got freezing rain. The
gutters kept the eves cold enough to freeze the saturated snow,
then the rain backed up behind that.

I keep saying that I'll put emergency heating cables in the gutters.
Maybe next year.

--
Drew Lawson | And to those who lack the courage
| And say it's dangerous to try
| Well they just don't know
| That love eternal will not be denied