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.