A properly insulated attic will prevent moisture accumulation. Attics may be ventilated with a combination of soffit vents at eaves and continuous ridge vents. Attic vents may also be installed in gable faces. The net free area of a vent is smaller than its overall dimension because part of the vent opening is blocked by meshes or louvers. The openings should be equally distributed between the soffit and ridge vents or between each gable face. Never cover or block vents with insulation. Take care to prevent loose-fill insulation from clogging vents by using baffles.

Adequate ventilation in your house is important for two reasons:

• Moisture Control - Ventilation will prevent moisture levels from rising within the conditioned space during the heating season. Elevated levels of moisture in a home can lead to condensation on window surfaces and give rise to surface mold and mildew.

Avoiding Indoor Air Pollution - When natural ventilation has been sharply reduced, as in super-energy-efficient houses, it may be necessary to provide fresh air ventilation to avoid build-up of stale air and indoor air pollutants. Special air exchange units with heat-saving features are available for this purpose.