Ice Dams and Icicles, Preventing Roof Edge Ice Damming


How to prevent roof ice dams formation

Roof ice dams formation along the edges of your home roof and icicles hanging from the gutters and / or soffits should never be ignored. Their beauty on the exterior has roots penetrating your house attic and wall structures, often causing significant damage.

There are three main things responsible for roof ice dams:

  1. Inadequate / improper house attic insulation
  2. Inadequate house attic ventilation
  3. Heat sources in attic area

Roof ice dams and icicles caused by missing wall and floor insulation in attic areaAny areas between the attic and living space that are missing or have a low amount of insulation permit unwanted heat to transfer from the house into the unheated attic.

Warmer air elevates the roof deck temperature directly above the “leak” and causes snow to melt onto the roof surface. Water running down the roof towards the area along the gutters / over the soffits starts re-freezing (soffits and gutters are colder than the rest of the roof surface because they hang over the house edge), creating roof ice dams.

Roof ice dams and icicles caused by missing soffit vents and low attic insulation levelResults of roof ice dams caused by a poor soffit ventilationWater from melting snow and ice forms icicles; some of the water below and above the ice dam will find its way back under the shingle surfaces. If your roof has no ice & water shield installed (older roofs rarely have that), the roof deck becomes soaked with water and eventually mold starts growing on its surface. In some roof / house structure designs, water from the roof ice dams might start dripping into the wall cavity located directly underneath it.

Continuous soffit vent significantly improves attic ventilation and helps preventing roof ice damsRoof - attic power and passive vents help preventing roof ice damsIf you have any heat sources in the house attic like improperly installed bathroom vents, heating ducts, gaps around the attic floor penetrations, etc., you are dramatically increasing your chances for roof ice dams formation.

Properly designed attic ventilation, including plenty of soffit / drip edge vents and roof top vents, may be able to remove the excess of heat and prevent roof ice dams from appearing on your roof. However, by leaving leaks as they are, you are wasting expensive energy.

Snow melting on roof surface due to missing attic insulationObserve your roof after the snowfall. If you notice snow disappearing from the roof surface in certain areas – check the attic. The main problem should be directly below that spot where the snow has already melted. It may take only a little effort to find it, but be extremely careful when evaluating the attic – don’t do it if you are not 100% comfortable with it!

It doesn’t take much snow on the roof to create serious conditions in the attic and roof ice dams on the exterior. If you chose to ignore it, though, it might require a lot of effort and money to fix it.

Roof and gutter heating cables – they help to eliminate roof ice dams, and might be your only solution for some types of roofs. However, if your house has an accessible attic, and poor attic ventilation is responsible for roof ice dams – correct the problem. It might not be cheaper, but it will also help to keep your house cooler during the summer.

Check your attic periodically, if you notice roof ice dams forming along the edges of your roof, that’s where you have to go to fix this problem.

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