Ask Adam: What’s An Attic Fan?

Attic Fan

Many homes today still have a fan in the attic called a Power Attic Ventilator or PAV.

Years ago, the thinking was that a fan in the attic would cool the attic and reduce the running time of the A/C unit.

Modern building science has proven that an attic fan is more detrimental to your overall comfort than it is beneficial. Most attic floors are very leaky with many penetrations (can lights, plumbing stacks, conduit, etc.). Therefore the air that is pulled from the attic is mostly from the inside of your home. This air has to be replaced by bringing in unwanted hot air from outside. This process is called infiltration.

Power Attic Ventilator or PAV

This will now introduce particulates, contaminants, and humidity into the house. This explains why many homes are always dusty even though the doors and windows are closed while the A/C is running.

Attic ventilation is a code requirement but is more of a wintertime concern due to humidity escaping from the home. Passive ventilation is more than adequate to vent the attic and prevent building degradation.

attic fan - mchenry heating - heating woodstock

If you have any HVAC related questions, contact me today! Call me direct at 815-220-5125 or email me at

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