Control bath humidity with a medium-tech digital fan timer

As homes are designed and built to be more air tight, mechanical ventilation becomes a necessity. Once a bastion of high-performance green homes, mechanical ventilation systems have made their way into the spec sheets for many production builders. But even in homes with whole-house automated ventilation systems that constantly supply the structure with a flow of fresh air, the bath is often equipped with simple on-off switch for control of the overhead exhaust fan. These fans are critical to maintaining interior air quality as they are designed to evacuate the mass of humid air that ensues as the shower is used or the bath tub is filled.

“You really want to get that huge amount of humid air in your bath out of the house,” says Jonathan Clow, a founding partner of Strong Roots Development, an Austin, Texas-based firm that specializes in the construction of high-performance, climate-appropriate homes. “So the best way to do that is to set a fan timer for 30 minutes before you get into the shower.”

The Eaton Aspire 5-Button Preset Timer Switch is a direct retrofit for any standard 3-wire wall switch, and has LEDs behind each button that illuminate upon touch. Image: Digitized House Media.

Reducing the humidity in your bath is one of the best ways to help prevent the formation of mold—a decidedly unhealthy proposition—and that is where fans come in. And one of the best ways to operate your bath fan for the recommended 30 minutes is by retrofitting the wall switch to a digital timer, a nice upgrade over the twist-to-set mechanical fan timers that are widely available. There are many choices here, but we have found one of the best solutions to be the Eaton Aspire 5-Button Preset Timer Switch (item number 9590), a roughly-$27 digital timer equipped with 5 simple preset buttons to run the fan for 5, 10, 15, 30, or 60 minutes.

This switch is easy to install in most homes, and its 15-amp, 1800-watt capacity will work with most standard overhead bath fans rated up to 1/4 horsepower. This is a non-smart switch, meaning you cannot connect it to home automation system or control it with a voice activation command. There may be some smart switches available here, but they may be overkill for this application. Also be aware many digital in-wall timer switches are designed strictly for lighting and are not compatible with fan motors, so be sure to double-check the specs of any timer before buying.

Designed to fit behind Decora-style wall plates, the Eaton Aspire switch sells for about $27. They are an excellent way to control your bath fan and evacuate humid air. Image: Digitized House Media.

With its standard 3-wire connection (with 2 power wires and one ground wire), the Eaton Aspire switch is an easy one-for-one swap for standard single-pole toggle or rocker switches and does not require a separate neutral wire like many other fan switches. The install begins by first switching off the circuit breaker in the home’s electrical control panel that controls power to the fan, then removing the outlet cover plate and de-installing the old switch. Using the supplied twist connectors, connect the wires to the new switch, replace the screws, re-install the cover plate, and switch the circuit breaker back on. If you are not comfortable with touching the wiring system in the walls of your home, by all means consult an electrical profesional for the work.

A small LED on the power button lights up to tell you the switch is properly connected, and the fan can be turned on by simply touching one of the 5 timer buttons—activating an LED in the respective button as a visual cue. As a nice touch, the timer counts down by progressively lighting an LED in the buttons above it. You can turn the fan off at any time by pressing the power button on the right.

If your home is not fitted with Decora-style outlet covers, you will need one of those for the Eaton Aspire timer as they follow the Decora design spec. These look best when mated with other modern Decora-style switches.

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