Pairing a whole house fan with an attic fan in the Phoenix Valley is a wise strategy because they are complementary systems that tackle different aspects of the cooling challenge at different times of the day.
They work together to maximize efficiency and comfort by ensuring both the house and the attic are cooled effectively throughout the entire 24-hour cycle.
1. Complementary Roles (Day vs. Night)
The key to the pairing is that the two fans perform their primary cooling function during separate periods:
Fan Type Primary Role When It Runs What It Achieves
Whole
House Fan Cooling the Living Space Evenings, Night, & Early Morning (when outside air is cool) Flushes hot air out of the house, pulls in cool, fresh air through windows, and pre-cools the thermal mass of the home.
Attic Fan Cooling the Attic Structure Hottest Part of the Day (thermostatically controlled) Actively exhausts the scorching hot air that builds up in the attic (which can exceed 150∘F), preventing it from radiating down into the living space.
2. Enhancing Whole House Fan Performance
The whole house fan’s job is to quickly push all the air from the living space into the attic, and then out of the house.
· Prevents Attic Pressurization: Whole house fans move a massive amount of air. If the attic lacks sufficient passive ventilation (like soffit and ridge vents), the rapid influx of air from the house can “pressurize” the attic. This back-pressure reduces the whole house fan’s efficiency and, critically, can force the hot attic air down through cracks and ceiling penetrations into the living space—negating the fan’s benefit.
· Active Assist: An attic fan acts as a powerful, active exhaust vent. When the whole house fan is running, the attic fan helps pull the air out of the attic quickly, ensuring the whole house fan can operate at maximum efficiency without building up counter-pressure.
3. Lowering Daytime AC Load
The attic fan’s primary benefit is strictly about heat mitigation during the day:
· Reduces Heat Transfer: By running the attic fan when attic temperatures climb (even while the house is sealed and the AC is running), it keeps the attic closer to the ambient outdoor
temperature. This reduces the heat radiating down through the ceiling and ductwork, which in turn reduces the workload on your AC unit, saving energy and extending the AC system’s life.
By installing both, you achieve the following cycle:
1. Daytime: The Attic Fan runs to minimize the heat gain on the house structure, making the AC’s job easier.
2. Nighttime: The Whole House Fan runs to flush the house with cool night air, drastically lowering the home’s core temperature for free, reducing the need for AC the following morning. Here is a link to a good video explaining this process.
Give us a call today, 623-869-6922, to find out more.