Attic Vents & Fans
Attic ventilation shouldn't require electricity
Research has shown that attic ventilation improves energy efficiency and helps to prevent ice dams from forming along eaves during the winter. Good attic ventilation is also necessary to avoid mold and moisture damage, and to prolong the life of roof shingles.
"Active" attic ventilation refers to electrically powered fans that exhaust air from the attic. An electric fan used for attic ventilation is also sometimes referred to as a powered attic ventilator, or PAV. "Passive" attic ventilation doesn't require electricity, relying instead on air currents and natural convection to move air through different types of attic vents.
In many older homes, PAVs were installed in the gable end of the house and connected to a thermostat that would turn on the fan when the attic reached a preset temperature. Another type of PAV is a whole-house fan typically mounted in a hallway ceiling and designed to exhaust hot interior air through the attic. A third type of PAV can be mounted directly on the roof. Some roof-mounted PAVs are solar-powered. But regardless of their location or electricity source, PAVs are not necessary to achieve adequate attic ventilation, and they can even hurt energy performance by sucking conditioned (cooled) air out of the living space and into the attic.
In contrast to active attic ventilation that consumes energy, passive attic ventilation has proven to be efficient and reliable, providing that the right number and combination of attic vents are used. In most cases, a combination of soffit vents (installed along the eaves), ridge vents and gable-end vents are used to achieve adequate attic ventilation without any energy consumption. An experienced home energy analyst will be able to determine if your house has the right amount of ventilation from these vents. More vents can be installed if necessary, and wasteful, ineffective PAVs can be removed.
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