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Water Leakage

Problem: Mold and mildew growth.

Cause: Excessive humidity and cold spots.

When high humidity levels combine with cold spots on the wall or ceiling, the result can be mold and mildew growth. People find higher humidity levels more comfortable and often humidify their houses. Cold spots in corners where ceilings meet walls can occur due to inadequate insulation and wind washing. This provides an ideal environment for mold growth as shown in Figure 29.

Mold & Mildew Caused By Cold Corner

Figure 29 - Mold & Mildew Caused By Cold Corner

Note 1: Cold spot - condensation, mold and mildew.

Note 2: Wind washing.

Solutions: Increase ventilation to control humidity. Insulate properly and reduce wind washing.

  • Keep humidity levels low enough to prevent condensation on windows during winter months. You may also attain higher humidity levels by using improved wall and ceiling construction and high-efficiency windows.
  • Increase the amount of insulation over the exterior walls and ensure that the insulation goes right to the top of the outside walls. The use of high heel trusses will allow for greater depths of insulation to be installed at the outside walls.
  • Use insulation stops. These baffles prevent cold air from blowing the insulation out of place and they also keep the air from short-circuiting through the insulation. If air is moving through the insulation, it reduces the effectiveness of the insulation and creates a cold spot as shown in Figure 30.

Correct Construction Of Corner To Prevent Wind Washing

Figure 30 - Correct Construction Of Corner To Prevent Wind Washing

Note 1: Insulation baffle

Note 2: Extend building paper to underside of top truss or rafter chord.

Note 3: Exterior finish

Note 4: Drywall

Note 5: Air barrier

Additional information on mold and mildew

Additional information on roofs and roofing