Using the Dual Thermostat/Humidistat for Attic Fans
By We re still here！ | Published: 2026-10-27
Category: How-to Guides
Learn how the Dual Thermostat/Humidistat Control for Power Attic Ventilators automatically manages temperature and humidity, protecting your attic and reducing energy costs.
Quick Answer
The Dual Thermostat/Humidistat Control gives your power attic ventilator automatic temperature and humidity control, so the fan runs only when needed—reducing moisture, protecting roofing, and saving energy.
Why Automatic Control Matters
A power attic ventilator that runs on a simple switch or thermostat alone can leave your attic too humid in cool weather or run unnecessarily on mild days. The dual thermostat/humidistat combines two sensors in one unit, so the fan responds to both heat buildup and moisture levels. That means you get mold and mildew protection without wasting energy.
Mounting the control to a rafter keeps it out of the way and in a spot where it can sense the actual attic conditions. The included wiring diagram simplifies the connection, but you still need to follow local electrical codes and, if you're not comfortable with wiring, call a licensed electrician.
Trade-Offs to Consider
The dual control is more complex than a single thermostat, so setup takes a little more time. You'll need to set both the temperature and humidity thresholds, and you may need to adjust them seasonally. However, the added control usually pays off in lower energy costs and better protection for your roof structure.
If your attic fan is already wired to a simple switch, you can replace that switch with this control, but verify that the voltage and amperage ratings match your fan. The product page doesn't list those specs, so check your fan's label before ordering.
Step-by-Step Setup and Use
- Turn off power and mount the control: Shut off the circuit that feeds your attic fan. Mount the dual control to a rafter using wood screws, placing it where it can sense general attic conditions, not right next to a vent or in direct sunlight. A common mistake is mounting near a vent, which gives false readings.
- Wire the control according to the diagram: Follow the included wiring diagram to connect the control to your power attic ventilator. If the wiring looks unfamiliar or your fan's voltage doesn't match the control, stop and call an electrician. Double-check that power is off before touching wires.
- Set the temperature threshold: Adjust the thermostat dial to the temperature at which you want the fan to turn on—typically around 100–110°F. This prevents heat buildup that can damage roofing and make cooling your home harder. Don't set it too low, or the fan will run constantly and waste energy.
- Set the humidity threshold: Set the humidistat to the relative humidity level where moisture becomes a concern—often around 60–70%. This triggers the fan during damp conditions to prevent mold and mildew. If you live in a humid climate, you may need a lower setting.
- Test the system and adjust seasonally: Restore power and test the fan by temporarily adjusting the controls to trigger it. Then set them back. Revisit the settings as seasons change, because temperature and humidity needs shift. A quick seasonal check keeps the control effective and efficient.
Product Facts
- Dual Thermostat/Humidistat Control for Power Attic Ventilators: This control reduces both moisture and excess heat in your attic to avoid mold and mildew issues, prolong the life of roofing components, and reduce energy costs when paired with an electric attic fan. It gives you two-in-one protection, so you don't need separate controls or manual switching.
Dual Thermostat/Humidistat Control for Power Attic Ventilators - Dual Thermostat/Humidistat Control for Power Attic Ventilators: The controller mounts to a rafter using wood screws and includes a wiring diagram for installation. Mounting to a rafter keeps the sensor in the attic airspace, and the diagram helps you wire it correctly.
