Appendix A: Basic Information About Ice Dam Formation And Prevention - EasyHeat ADKS Serie Guia Del Usuario

X. APPENDIX A: BASIC INFORMATION ABOUT ICE DAM
FORMATION AND PREVENTION
A. HOW ICE DAMS FORM
Snow and ice on the roof can thaw because of heat loss through the roof
due to inadequate roof venting and/or insufficient ceiling insulation. In
these cases, the roof surface above heated areas of the building is warm
enough to melt the snow, while the roof surface above the overhang is
cool enough to refreeze this melt water as it trickles down the roof. As a
result, a layer of ice forms on this cooler, lower roof surface and in gut-
ters. As snow continues to melt, the melt water flows downward and
re-freezes at the roof edge. As this happens, ice builds up to several inches
in thickness forming an ice dam. In addition to having ice dams along the
roofline, structures such as skylights and dormers often have poor venting,
and ice dams may form in the surrounding areas.
B. SIGNS OF ICE DAMS
Ice dams can be identified at points where snow has melted on an upper
roof surface, but the roof area further down is still snow and/or ice covered.
Icicles are also a sign of ice dams.
C. DAMAGING RESULTS
Ice dams prevent water from flowing off the roof. The melt water will
instead "pond" at the ice dam, and can result in water seeping between
shingles. Water that has seeped under the shingles can leak through
roof penetrations, such as nail holes and sheathing seams, and inside the
building walls and ceiling. The water can also flow along ceiling beams
or wiring. Eventually, water can leak into the building interior at light
fixtures or through the ceiling finishing at places other than below the ice
dam's origin.
In addition, ice buildup in gutters can put significant stress on the gutter
resulting in gutter damage
D. HOW TO AVOID ICE DAMS
To avoid ice dams, the entire roof surface should be kept at about the
same temperature as the outside air. The best way to do this is to ventilate
the space under the roof. However, this is often costly or impractical. In
these cases, deicing cables can provide a reasonable solution to ice dam
problems. Placing deicing cable on the roof edge above the overhang and in
the gutter and downspouts prevents melt water from refreezing. This allows
the melt water to have a clear path to flow to the ground and prevents
leaking into your home interior or damage to your gutter system.
ADKS Owner's Manual
Figure A-1. Roof heat creates potential for ice dams to form
Figure A-2. Ice dam formation and the consequences
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