Why Bathroom Fans are a Bad Idea

by Cody Farmer

Air Tight Construction Colorado

We are always ranting about how our ERVs clean up the interior air all the while saving up to 90% of the energy. In our application of the Passive House principles, we replace the bathroom fan with a recovery exhaust duct. We’ve not really discussed how this works, where the bathroom fan does not. It is our opinion that the bathroom fan removes one pollutant while bringing in another.


Bathroom fans are code required these days even in bathrooms with windows. For every bathroom fan in a building, there is a hole in the exterior wall letting 40-60 cubic feet per minute of air out of the building. It’s basically like opening a window and forcing a lot of air out of the building. That’s issue number one with the bathroom fan. They let air out, but not in!

Bathroom fans only work when they are on. Most people leave the bathroom and turn off the bathroom fan long before the shower steam or worse the smell of number TWO is gone! That’s right, bathroom fans don’t stay on long enough to fully refresh the bathroom. 

Bathroom fans are noisy. This causes people to not use them. Although that saves the energy that heated or cooled the air, it also saves the humidity of a shower or the smell of a deuce.  When turned on the bathroom fan loses all the energy of the air. 

I really enjoyed the benefits of having an ERV when my Children (who were too small to turn on light switches) would do the stinky in our office. Although they could close the door, they couldn’t turn on a light switch or a bathroom fan. Luckily, we have the Zehnder ERV working all the time, so we never smell any restroom smells.

Air Tight Construction Colorado

Along with reducing odors, a Zehnder unit will also accomplish several important goals:

  • - Reduce condensation.
  • - Regulate temperature.
  • - Lower concentrations of radon gas and VOCs.
  • - Filter out allergens.
  • - Reduce backdraft risks.
  • - Lower your energy bills.

If you’re interested in seeing what an ERV can do for your home, fill out the simple request form here and we’ll give you a customized plan specifically designed for your home!