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Water Leakage

Problem: Wet ceilings due to attic condensation.

Cause: Air leakage

Warm, moist air leaks from the interior of the house into the attic space through gaps in the air barrier. When this moist air enters the cold attic, the moisture freezes onto cold surfaces such as roof sheathing and framing members. When the attic space warms, the ice melts and makes its way back to the ceiling drywall, resulting in wetting and damage as shown in Figure 28.

Wet Ceilings Caused By Attic Condensation

Figure 28 - Wet Ceilings Caused By Attic Condensation

Note 1: Condensation forms on framing members, sheathing and underside of roof covering.

Note 2: Condensation pooling on ceiling.

Note 3: Air leakage: Warm, humid indoor air leaks through holes.

Solutions: Install a continuous air barrier and ventilate the attic.

  • Air barriers must be continuous with no holes. They reduce the amount of moisture that can make its way into the attic. Positive air pressure at the ceiling level will force moisture-laden air into the attic. Reducing the number of penetrations in the ceiling air barrier will increase the integrity of the air barrier. Employing polyethylene boxes around lighting outlets and gaskets around stacks and vents; eliminating or weather stripping interior attic accesses; and using acoustic caulking at all joints will substantially improve the air barrier and reduce moisture problems.
  • Ventilating the attic space will minimize the effects of the moisture that does make its way into the attic. Ventilation allows the attic space to dry out after condensation and melting take place. Providing ventilation in accordance with local building codes and ensuring that insulation stops are installed properly will help minimize moisture problems.

Additional information on roofs and roofing

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