What practice helps prevent ice damming when insulating above the ceiling?

• A. Sealing all ventilation in attic.
• B. Installing insulation only at ceiling joists with no ventilation.
• C. Keeping ventilation paths open (baffles) and preventing insulation from blocking soffit vents to ensure continuous airflow.
• D. Removing all attic insulation to reduce moisture.

Answer: (C)

Preventing ice damming hinges on keeping the roof cold by providing continuous attic ventilation. Warm air from the living space can heat the underside of the roof sheathing, causing snow to melt near the eaves. The melted water then refreezes at the cold edge, forming an ice dam. The best way to stop this is to maintain clear ventilation paths from the soffit to the ridge so outdoor air can continuously flow under the roof sheathing. Using baffles creates an unobstructed channel that keeps insulation from blocking soffit vents, ensuring the air can move all the way to the attic exhaust. With this continuous airflow, the roof stays cooler in winter, reducing melt near the eaves and preventing ice dams. Sealing off ventilation or insulating without keeping ventilation paths open would trap heat and moisture, making ice damming more likely, while removing attic insulation would lead to other problems without addressing the dam.