Ventilating a Bathroom without Windows: How to Prevent Mold…

Bathrooms are particularly prone to mold. To prevent this, ventilation is key. But what if your bathroom was built without windows?

Excessive moisture in the home leads to mold, which can damage the structure and harm health. To prevent mold from forming on the walls, many bathrooms have windows. These are opened after showering or bathing to expel the humid air outside. But what should you do if the bathroom lacks windows? How do you ventilate these spaces?

Do Bathrooms without Windows Require Ventilation Systems?

In such cases, ventilation systems come to the rescue. They lead air outside through a duct, facilitating air exchange to ventilate the windowless bathroom. These systems can also be installed retroactively on the exterior wall: no exhaust pipes need to be laid; you only need to perform a core drilling or a wall breakthrough for the duct.

Ventilation systems with heat recovery extract heat from the exhaust air and transfer it to the incoming fresh air, eliminating the need for additional heating. Modern devices can also measure the humidity and temperature in the room, activating automatically when necessary.

If the bathroom is not directly adjacent to an exterior wall, it may have a central exhaust system. This system is connected to a ventilation shaft or an unused pipe connection and expels the exhaust air outside. However, fresh air does not flow into the bathroom through this system; this is regulated through air vents or the bathroom door. Heat recovery is not possible with this setup. However, these systems are usually easy to install without much effort.

Ventilating a Bathroom without Windows: 5 Additional Tips

If you still struggle with moisture in the bathroom despite ventilation, consider taking the following measures:

  1. Dry tiles after showering with a squeegee to prevent moisture from seeping into the grout.
  2. Dry damp towels in another room that is not already humid. If you have a balcony, you can use it—even in winter.
  3. Exchange air by opening one (or more) window in a room adjacent to the bathroom. Keep internal doors open, but doors to other rooms should be closed. With open windows, moist indoor air can be exchanged with dry outdoor air. Air exchange works particularly well when the outside air is colder than the indoor air. However, do not leave the windows open for too long to avoid cooling down the apartment excessively.
  4. Use a hygrometer to monitor humidity levels. A relative humidity of 40-70 percent in the bathroom is acceptable. If the value exceeds this range, take corrective action.
  5. Use dehumidifiers if none of the above solutions adequately ventilate the windowless bathroom. These devices can extract several liters of water from the air. However, electric dehumidifiers consume power, incurring costs. Chemical dehumidifiers absorb humidity in granules, operating without electricity. However, you need to replace the granules regularly, which also incurs costs.

These measures should be sufficient to prevent mold in your bathroom. However, if you want to be sure, you can conduct a mold test. With a test kit, you can take a sample yourself, which is then analyzed in a laboratory.