How they are formed?
Ice dams are formed when the snow on the roof is melted
by the heat escaping out from the house or by the action of sun. The melting
occurs mostly at the roof and not at the projected eaves. Water from the
melting snow can then freeze and form ice dams at the eaves trough and roof
overhang. This ice will prevent and block the water from the melted snow to
flow to the gutters. The water then finds it way under the shingles and thus
leaking into the attic.
What problems they
cause?
·
The main problem caused by ice dam is the
water penetration into the attic and thus causing water damage at various areas
of the house.
·
Rotting of roof sheathing, walls, framing
and peeling paint.
·
Mold growth which can result in various
respiratory illnesses.
·
The R value which measures the resistance
of the insulation for transmission of heat is also reduced when insulation is
wet. This will further deteriorate the thermal performance and more heat from
house will leak to the roof. This will result in more ice dams.
How to prevent its
formation?
·
Roof should be properly vented to keep the
underside of the roof cold and also to remove the heat which has leaked into
the attic from the house.
·
Increase the thickness of insulation in the
attic
·
Properly seal all the openings and
penetration from the house to attic sealing to prevent heat from leaking into
the attic.
·
Install vapour barrier under the insulation
facing downwards towards the room to prevent water vapour escaping into the
attic.
·
Extend exhaust systems that terminates just
above the roof, to prevent melting of the snow.
·
There should be minimum three inches of gap
between the insulation and the roof sheathing at the sloped roof areas.
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