Why should power vents not be operated in winter?

Power vents should not be operated in winter primarily because they can depressurize the attic space, which allows warm, moist air from the living areas of the home to infiltrate into the attic. During colder months, the attic is generally intended to remain at a lower temperature to prevent moisture buildup and condensation, which can lead to issues like mold growth and ice dam formation on the roof.

Operating power vents in winter can create a vacuum effect that pulls this warm air into the attic. When this warm, moist air comes into contact with the cold surfaces within the attic, it can condense and contribute to moisture problems. Ideally, vents should work in conjunction with the natural thermal dynamics of the home, maintaining a balance that prevents any warm air from entering where it could cause damage.

In contrast, overheating the attic, ice build-up, or insufficient ventilation are related concerns but do not directly address the specific risks associated with the operation of power vents during the colder months. Each of those options discusses different aspects of ventilation issues, but the primary action of power vents impacting attic pressure is the key reason for their restricted use in winter.