Ice Dam Potential Damage
Roof leaks wet attic insulation. In the short term, wet insulation doesn't work well. Over the long term, water-soaked insulation remains compressed, so that even after it dries, the insulation in the ceiling is not as thick. The lower R-values become part of a vicious cycle: heat loss-ice dams-leaks-insulation damage-more heat loss! Cellulose insulation is particularly vulnerable to the hazards of wetting.
Water often leaks down within the wall frame, where it wets wall insulation and causes it to sag, leaving uninsulated voids at the top of the wall. Again, energy dollars disappear, but more importantly, moisture gets trapped within the wall cavity between the exterior plywood sheathing and the interior vapor barrier, causing smelly, rotting wall cavities. Structural framing members can decay. Metal fasteners may corrode. Mold and mildew can form on wall surfaces as a result of elevated humidity levels. Both exterior and interior paint blister and peel. And people with allergies suffer.
Peeling wall paint deserves special attention because its cause may be difficult to recognize. It is unlikely that wall paint will blister or peel when ice dams are visible. Paint peels long after the ice and the roof leak itself have disappeared. Water from the leak infiltrates wall cavities. It dampens building materials and raises the relative humidity within wall frames. The moisture within the wall cavity eventually wets interior wall coverings and exterior claddings as it tries to escape (as either liquid or vapor). As a result, interior and exterior walls shed their skin of paint.