Michigan's Residential Code requires that attics be ventilated, allowing the moisture that accumulates in the conditioned space to vent outdoors. In addition, ventilation helps maintain a cold roof temperature, which reduces the occurrence of ice dams created by melting snow, a common problem in Michigan.

However, when the ventilated air moves across or through a structure, typically entering through the roof's outside corners or eaves, that airflow and the moisture it carries reduces the attic insulation's performance effectiveness. This phenomenon is called wind-washing, and can result in significant heat loss.

Sealed attic systems reduce air movement through the conditioned spaces of the attic, reducing energy loss and improving attic moisture control, while still providing a ventilated roof system.

Some Michigan Code Officials have expressed concern over whether membranes used to seal the attic still allow vapor to pass through. A new breathable membrane product on the market has a perm rating of more than 20, allowing water vapor to escape.

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