Ventilation is different from insulation

In a conventionally vented attic, outside air enters through designed intake openings and leaves through designed exhaust openings. Soffit intake and ridge exhaust are one common arrangement. Insulation slows heat transfer between indoors and outdoors. Air sealing limits unwanted air leakage from the living space. These are related building functions, but one does not replace the others.

Blocked intake can undermine the intended airflow path. Adding more exhaust without checking intake and the whole attic design is not a complete solution. Bathroom or kitchen exhaust should not dump moisture into an attic. Some homes use deliberately unvented conditioned roof assemblies; a vented-attic rule should not be imposed on them without professional review.

In snowy climates, heat escaping into an attic can contribute to roof snow melting and refreezing near cold edges. Ice-dam prevention is a building-envelope question, involving air leakage and insulation as well as roof details. A membrane may limit water entry but does not correct the heat-loss mechanism.