Thread: Ice Damming?
View Single Post
Old 01-07-2022, 12:03 PM   #12
DickR
Senior Member
 
Join Date: Apr 2008
Location: Moultonborough
Posts: 734
Thanks: 4
Thanked 254 Times in 166 Posts
Default

While there are weather sequences, like snow-rain-cold, that can lead to ice formation at the eaves, a great deal of ice formation there is due to house construction issues resulting in heat leakage into the attic or insulated cavities in the case of cathedral ceilings. Everyone likely has noticed cases of ice dams and arrays of icicles hanging down on a house, while an unoccupied/unheated garage or other structure nearby holds the snow on the roof much longer, with little or no ice at the eaves.

In new house construction, roof ice issues can largely be avoided by establishing a continuous air barrier at least at the upper level, to eliminate totally having interior air leaking up and getting at the underside of the roof deck. Common leakage points are wiring holes in top plates, can lights in the ceiling, and attic access hatch openings.

In existing construction, a lot of such leaks can be closed off by a thorough effort at uncovering insulation to expose wiring penetrations and sealing them with can foam. Can lights can be replaced with shallow LED fixtures, sealed properly. Attic hatchways can be improved by better gasketing or by covering with after-the-fact kits designed to insulate and air-seal, such as this one:https://www.amazon.com/Attic-Stairwa...a-823482421655
(I have no idea how good that one is; it's just one of many to be found by searching on "attic hatchway insulation kit.").

Cathedral ceilings, too, can be problematic, but there are designs that work well. A good source of information can be found here: https://www.greenbuildingadvisor.com...hedral+ceiling
although many of those articles are behind a pay wall. Another good source is here: https://www.buildingscience.com/docu...of-design/view
That site has other good articles on the subject.
DickR is offline   Reply With Quote
The Following 4 Users Say Thank You to DickR For This Useful Post: