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Ice
Dams
Defending Your Home
Against Ice Dams
To reduce the possibility of ice dams, VentMASTER
uses a three-step approach:
1. Adequate attic ventilation
Because ice dams form when a roof has warmed upper surfaces
and cold lower surfaces, the solution is to equalize temperatures
over the entire roof. The most effective way to equalize temperatures
is to create a cold roof.
To do that, you need a well designed attic
ventilation system that will supply airflow along the entire
underside of the roof deck. That's critical, because only uniformly
distributed airflow can reduce variation in roof temperatures
from peak to eave.
One of the most efficient and effective
systems (from both coast and performance standpoints) uses ridge
vents and an evenly distributed layout of intake vents.
2. Adequate attic insulation
Attic insulation serves two purposes. First, it reduces heat
loss from a home's living quarters. Since that heat loss is
a key factor contributing to the creation of ice dams, stopping
it at its source is critical. Second, adequate attic insulation
diminishes the energy impact of having cold air flowing through
the attic.
3. Waterproofing shingle underlayment
(WSU)
Event he most efficient attic ventilation system may not be
enough to eliminate ice dams. A combination of weather conditions,
roof pitch, building orientation, and other factors may allow
ice dams to form under certain conditions. If that happens,
a WSU barrier can minimize - and possibly eliminate - water
infiltration into the building structure.
Heat Cables
Using heat cables to melt ice
on a troubled roof where heat escaping from the house has already
produced the potential for ice dams is like using a band aid
after open heart surgery. Why?
- Heat tape can only melt ice a few inches
from the cable, which leaves many areas unprotected.
- The zigzag melting pattern creates limited
and selective removal of snow and ice that causes up-roof
ice dams.
- Unlike a passive system of soffit and ridge
vents with good insulation, which need no constant monitoring,
you have to be home to turn on the cables (no winter vacations!).
- Possible fire hazard.
- They can ruin the look of your house.
- The cost: installation of cables is often
more expensive than installing insulation and ventilation
in the attic. Also, the energy costs for operating
heat cable significant; on-going and RISING!
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