Ask An Engineer: What’s The Point of a Bathroom Fan?

We've launched a new feature on SHP.com: Ask An ______. The series is just what you'd expect: you ask the questions, and we turn to our best and brightest interior designers, engineers and architects to get the answers.

Our next installment features mechanical engineer Jacob Faiola.

The intended purpose for the vented bathroom fan is a debate as old as time itself—or at the very least since bathroom fans became a staple in most American homes. The argument is usually divided into two sides: those who believe the fan is there to remove moisture from the bathroom and those who think it is designed to remove any and all foul odors that may linger if not for a vented fan. But which side is correct? Which side can now claim the ultimate bragging rights? According to Jacob, it’s both!

“We are looking at the quintessential win-win situation. Both sides are right,” said Jacob.

The Purpose

Vented bathroom fans do a lot of good for your bathroom, which is why most modern building codes require their installation before the building can be considered complete. Some bathrooms will not require a vented fan after a remodel or construction if the room also has operating windows. Still, installing a fan is a good idea regardless of how large the bathroom is or how well it was designed.

According to Jacob, one of the primary functions of a bathroom fan is to remove any unwanted odors, but another (and possibly more important) function is to remove warm and moist air that tends to build up in our restrooms after using the shower or the bathtub. Dehumidification is critical, otherwise, you risk mold buildup as well as damage to bathroom fixtures and surfaces.

How They Work

A vent fan is typically wired very similarly to how ceiling light fixtures are. They are usually connected to the household electrical current, possibly to the same electrical current that powers the overhead light fixture. (In this case, both the light and the fan are turned on by one simple flip of the switch.)

Once the fan is turned on, air is drawn out through the vent and is displaced outside the home through an opening on either the roof or an exterior wall.

If you do not currently have a bathroom fan installed, check the room for a musty smell or signs of damaged bathroom walls, floors, ceilings or bathroom fixtures. Since the bathroom is a perfect environment for mold and mildew buildup, we suggest having fans installed.

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