The issue (ice dams) is caused by bad architecture, specifically the shape of the roof and/or the design of the house’s thermal envelope.
A properly designed roof should not have ice dams because the whole roof should get uniformly cold (below freezing) when the air temperature drops and the roof itself should not have any areas where meltwater can gather and refreeze.
My house violates both of these criteria. It has 2 different roof lines that meet at a right angle, resulting in a saddle point where tons of meltwater can gather. It also has a leaky thermal envelope that causes snow and ice to melt higher up on the roof and then refreeze in the gutters (which will always be cold because they hang outside the thermal envelope).
An ideal roof has a single roof line (think of a simple rectangular house with one peak in the middle) and the roof itself is raised several inches above a secondary plywood roof enclosing the insulation (with the thermal envelope inside) and ventilation allowing cold outdoor air to circulate between the two layers. This gives a pretty uniformly cold roof that maximizes drainage uniformity (no gathering of meltwater until the gutters). As long as the gutters and downspouts are free of clogs there should be no issues with ice dams.
Not a lot of people here use them, but it’s not uncommon to see it on a businesses roof. Like a restaurant. Look around some time, you might be surprised. I’m in Wisconsin.
Bizarre. I live in a cold climate (Alberta) and have never seen something like this.
I’ve seen it lots. I live in Ontario.
The issue (ice dams) is caused by bad architecture, specifically the shape of the roof and/or the design of the house’s thermal envelope.
A properly designed roof should not have ice dams because the whole roof should get uniformly cold (below freezing) when the air temperature drops and the roof itself should not have any areas where meltwater can gather and refreeze.
My house violates both of these criteria. It has 2 different roof lines that meet at a right angle, resulting in a saddle point where tons of meltwater can gather. It also has a leaky thermal envelope that causes snow and ice to melt higher up on the roof and then refreeze in the gutters (which will always be cold because they hang outside the thermal envelope).
An ideal roof has a single roof line (think of a simple rectangular house with one peak in the middle) and the roof itself is raised several inches above a secondary plywood roof enclosing the insulation (with the thermal envelope inside) and ventilation allowing cold outdoor air to circulate between the two layers. This gives a pretty uniformly cold roof that maximizes drainage uniformity (no gathering of meltwater until the gutters). As long as the gutters and downspouts are free of clogs there should be no issues with ice dams.
Not a lot of people here use them, but it’s not uncommon to see it on a businesses roof. Like a restaurant. Look around some time, you might be surprised. I’m in Wisconsin.
Hello fellow dull midwestern man. I’ve been needing to put some up on my roof but the ice dams haven’t melted yet.
50-70s houses used shallower roofs. The adoption of steel plates in trusses in the 80s let houses have much steeper pitches to prevent this issue.
Some houses in the US Midwest are over 100yo so there’s likely plenty of places that could stand to benefit.
I see this stuff in Ontario but pretty much only when somebody wants to clear the space above a walkway for safety reasons