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Attic Ventilation

One of the most frequent and least recognized problems home owners face is inadequate attic ventilation. Poor attic ventilation can lead to excessive heat in summer, which will prematurely fatigue a roof and require additional cooling for the living spaces below. During winter, moisture from indoor activities migrates from the living spaces to the attic - delaminating plywood and rotting roof sheathing and framing,

Rusted nails and stained roof sheathing are initial signs of a ventilation problem. Two tests help determine if there is sufficient ventilation in an attic. In the winter, look for moisture or frost on exposed nails at the underside of the roof sheathing during very cold weather. On warm, windless summer days there should be a maximum 10-15 degree difference between the air in the attic and a shady spot outside.

Solutions for poor ventilation include:

Ventilation Systems: Ridge and soffit vents allow natural air flow. Cool air enters at the soffits under the exterior roof overhangs. As this air warms, natural convection pushes it to the

Power Fans: During summer operation, a thermostat automatically operates a roof or gable-mounted fan as needed to force air circulation. For proper moisture control in winter, the fan should be operated by a humidistat placed at the lowest point in the attic on the north side, or a clock timer set for two minutes each hour during cold weather.

Blocked Vents: Clearing up blocked soffit vents often cures ventilation problems.

Adequate attic ventilation all year 'round is important to the long-term health of your house and for optimum interior comfort. It will also reduce heating and cooling loads and the expenses that go along with them.