Your attic has a microclimate all its own. On a hot summer day, attic temperatures can soar to 150 degrees as solar heat radiating through the roof accumulates in the enclosed space. This heat conducts through the ceiling and forces your air conditioner to run longer cycles to meet thermostat settings, raising operating costs. In winter, warm, damp air rising from rooms below collects in the attic and condenses when temperatures plunge at night. Moisture from this condensation saturates attic insulation, promotes mold growth and can damage wooden structural members. The remedy to acute attic temperatures and humidity is increased ventilation.
Most homes are designed with passive attic ventilation that uses vent openings at the soffits under the eaves and at the gables and roof peak. Hot air naturally rising in the attic exhausts through the gable and roof vents. This upward motion of air creates a “chimney effect” of low pressure inside the attic that sucks in cooler outside air through the soffit vents below, establishing a continuous circulation to exhaust heat and humidity.
Soffit Vent Fans
When passive methods aren’t sufficient, an electric fan installed at a soffit vent draws additional outside air into the attic to augment the chimney effect. This exhausts a greater volume of hot, moist air from the attic in summer and winter. Soffit fans are internally mounted inside the eave and use existing soffit vent openings. Fans may be solar powered by a small roof-mounted photovoltaic panel or hardwired to house current.
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