This only occurs when part of your roof warms to above 32 degrees f warm enough to melt the snow while the roof edge remains below freezing.
Ice dam no attic.
Because most of my advice is for people who have attics and you ve got a cathedral ceiling you simply don t have an attic.
Ice dams and icicles form when the snow melts runs down your roof and refreezes near the edge.
There are two main purposes of attic ventilation.
In addition seal all the places that warm air can escape into the attic like areas with wires and plumbing lighting fixtures heating fixtures chimneys etc.
Although excess heat moving from the attic through the roof rapidly melts snow once the meltwater touches the cold eaves it quickly freezes and forms an ice dam.
The bad news is you ll need a good contractor to help execute them.
If you have a furnace in the.
So the water above backs up behind the ice dam and remains a liquid.
By circulating cool outside air in the attic space or in the rafter spaces just below the roof deck the roof surface remains below freezing and cannot melt the snow on the roof.
Ventilation during the winter helps to reduce moisture as well as keeps attics dry and at an even temperature.
The result is that the snow on the roof melts unevenly usually leaving huge chunks of ice intact along the roof edge but with melted snow behind.
Excessive attic heat causes some areas of the roof to be warmer than others.
The dam grows as it is fed by the melting snow above it but it will limit itself to the portions of the roof that average below 32f.
Ask this old house general contractor tom silva explains the best ways to keep your roof and gutters free from those dreaded ice dams.
The cause of ice dams on the roof can be explained in two words excessive attic heat.
That s why attic fans are a non starter for ice dam prevention.
Ice dams can be a real problem in winter.
Proper attic ventilation can prevent ice dams.
To protect against damage to your structure and to reduce energy usage.
The good news is there are several ways you can prevent ice dams if you ve got a cathedral ceiling.
The tutorial how to prevent and remove ice dams describes what ice dams are and how you can try to prevent them from forming and damaging your home.
In the tutorial it also describes some of the preventative things you can do before winter including.
See below for a shopp.
This water finds cracks and openings in the exterior roof covering and flows into the attic space.
This scenario is often the result of a warm attic.
There are several means of improving attic ventilation.
