ice damming prevention

 have learned from another Permie the issue of ice damming  and the destruction it causes.
I was discussing a gutter system to catch rainwater and Catie explained the ice damming issue can wreck everything .
It was a shock to me.
But I found this comany that creates a hot edge and wondered if anybody knew about it?
hot edge
They have treatments for different types of roofing.

There are many such systems, but most are not much more than heat tape and a few clips to hold it. Earthships in the high desert do this, as much of their water comes as snow and will sublimate in the sun and not make it to the cistern without the melting system.

As I understand it, ice dams are primarily caused by air leaks from the house up into the attic that warm the roof deck and melt snow.  That snow melt runs down the roof until it hits a colder section of the roof deck, typically over the eaves.  There it freezes, forming a dam.  

So you can yell at your roofer all you want but the problem stems from a lack of good air sealing between the house and the attic.  Or heat from other hot things in the attic like a chimney or heating unit.

The terminolgy may be incorrect, I live in Australia where we have never heard of this phenominon, its when the ice builds up for any reason in the gutter
causing all sorts of issues, one of which is destruction of that same gutter.

Mike Haasl wrote:As I understand it, ice dams are primarily caused by air leaks from the house up into the attic that warm the roof deck and melt snow.  That snow melt runs down the roof until it hits a colder section of the roof deck, typically over the eaves.  There it freezes, forming a dam.  

So you can yell at your roofer all you want but the problem stems from a lack of good air sealing between the house and the attic.  Or heat from other hot things in the attic like a chimney or heating unit.

This is accurate; as a home inspector we are trained to look for ice damming or conditions that could lead to ice damming, and those conditions are exactly what you said: insufficient thermal barrier between conditioned space and attic space. The solution is to better insulate the conditioned space

There is a second cause of ice damming, which is when attic spaces are not properly vented. Due to the stack effect, relatively warm air can accumulate under the roof decking even if that warmth did not originate from inside the conditioned space. To prevent that you need nice big openings down low (i.e. in the eaves/soffits) for cooler air to enter and plenty of openings up high (i.e. near the ridge) for warmer air to escape. Best practice is to use soffit vents that are 100% perforated (they look kinda like pegboard, but made of aluminum) and ridge vents instead of just box vents or gable vents.

This is also a more "permie" solution because it uses simple physics and no moving or energized parts, unlike heat tape along the low edge of your roof which requires an extra energy input and is prone to failure and other issues (in addition to being a dead giveaway, when it comes time to sell your house, that you had ice damming problems).

A low tech solution may be roof snow cleats. My long north-facing roof would collect snow and ice that would sluff off in a big icy mess over the gutters. To prevent this, I bought a box of Snow Guard cleats that screw onto the roof about 2 feet up from the edge. This holds the bulk of the snow and ice up there so it can slowly melt and flow into the gutters, rather than slide into them all at once. No issues since installed.

And as a bonus, they were essential in giving me footing to install a chimney for a rocket mass heater!

I also installed snow cleats. I didn't love puncturing my metal roof, but hopefully the gasket will work. And it did wonders for preventing giant ice-curls from sliding off my roof in slow-mo.

A 3rd cause of ice dams is when you have a lower roof on the north side of the house and a higher roof where they had the downspout empty onto the lower roof, rather than spend the coin and have have two separate downspouts - one for each roof. (Northern Hemisphere)

The higher roof gets enough sun to warm up and melt, dumping that water onto the lower roof that gets *no* sun and then ice form in its eves trough.

Yes, some sort of heat tape helps decrease the risk. *Not ever* having a downspout empty onto another roof has upfront cost, but is likely to need minimal ongoing maintenance. Keeping roof lines as simple as possible will also help, but that's not the style these days, and sometimes it can be hard to avoid. Considering carefully the route the downspout could or should take, and where that water is going to is also important. Modern houses in my area have underground pipes taking downspout water right to the storm water drains. That has pros and cons. But having the downspout were it will likely get some sun is generally a better idea than it getting no sun.