Back to Healthy Homes for Healthy Humans

Bathroom ventilation is important for maintaining clean indoor air and preventing mold growth. Bathroom ventilation systems are designed to exhaust odors and moist air to the home’s exterior, rather than letting damp, stale air accumulate inside.

Bathroom fans vent polluted, stale indoor air to the outside.

Ventilation systems should be installed in all bathrooms, even bathrooms with windows, since windows will not be opened during the winter, spring and fall in Upper Michigan.

Bathroom ventilation fans should be periodically inspected for dust buildup that can impede air flow. Particles of moisture-laden animal dander and lint are attracted to the fan because of its static charge, and can easily get stuck in the air vents. To prevent dust buildup, simply wipe down the surface of the bathroom fan vent once or twice a month.

But sometimes, despite regular maintenance, bathroom ventilation systems don’t perform the way they’re supposed to. This usually indicates a defect of some kind. The most common defect related to bathroom ventilation systems is improper termination of the duct (meaning it doesn’t lead to outside, but rather a different part of your home, often the attic or inside a wall space), but it can be hard to know what’s going on for sure without a proper inspection.

The following conditions indicate insufficient bathroom ventilation:

  • moisture stains on walls or ceilings
  • corrosion of metal
  • visible mold on walls or ceilings
  • peeling paint or wallpaper
  • frost on windows
  • high levels of humidity

Improperly terminated ventilation systems may appear to work fine from inside the bathroom, so the inspector may have to look in the attic or on the roof. Sometimes, poorly installed ducts will loosen or become disconnected at joints or connections.

Improperly terminated vents can cause problems from condensation. Warm, moist air will condense on cold attic framing, insulation and other materials. This condition has the potential to cause health and/or decay problems from mold, or damage to building materials, such as drywall. Moisture also reduces the effectiveness of thermal insulation.

As unpleasant as all these consequences sound, perhaps the most serious consequence of an improper ventilation setup is mold. Moisture levels of about 20% in materials will cause mold colonies to grow. Inhaling mold spores can cause health problems in those with asthma or allergies, and can cause serious or fatal fungal infections in those with lung disease or compromised immune systems.

High moisture levels in building materials also contribute to rot. It’s hard to catch rot in the early stages; by the time it’s visible, as much as 50% of the material’s strength can be lost.

Above all else, a bathroom ventilation fan should be connected to a duct capable of venting water vapor and odors into the outdoors. Excessive moisture in the bathroom or mold growth within the bathroom or attic is a clear indication of improper ventilation that must be corrected in order to avoid structural decay and respiratory health issues.

Is your bathroom fan installed properly?

If you have any cause to believe your bathroom fan isn’t working properly, be sure to schedule an inspection right away.