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Optimal ventilation for the bathroom for high living comfort

Photo: © yu_photo /

Excessive humidity and unpleasant odours –– with the right ventilation concept for your bathroom, both can be avoided. Windows are not necessarily needed for this. Various technical solutions are available to provide ventilation in a bathroom without windows, which are often found in older buildings. But even in new buildings with bathroom windows, a ventilation system can be worthwhile. It provides a pleasant room climate and can reduce energy consumption at the same time. Learn more about the importance of ventilation, different solutions, and what to consider during repair and maintenance.

Air exchange in the bathroom is particularly important

As a rule, the humidity in bathrooms is higher than in other rooms. This is because a lot of moisture is produced when showering, bathing, washing clothes and drying wet towels. The problem here: If the temperature drops below the dew point, moisture condenses on cold surfaces, such as on external walls and in gaps. This favours mould. The exact dew point depends, among other things, on the air temperature and humidity. For example, at a room temperature of 24  degrees  Celsius and a humidity of 70  percent, it is 18.2  degrees  Celsius. Ventilation in the bathroom or an open window removes moisture before the temperature drops below the dew point and condensation occurs. Bathroom ventilation is not only a way to prevent mould. The air exchange also ensures that odours dissipate and living comfort is maintained.

Humidity and temperature of different rooms at a glance

The following table shows the ranges of optimum humidity and temperature in different living spaces. Both values are somewhat higher in the bathroom than in other rooms. The higher temperatures promote comfort in the bathroom, but as explained above, also help the air to bind more moisture. To prevent the humidity from condensing, it is therefore advisable to ensure an even temperature distribution in the bathroom.

Humidity in the bathroom

RoomOptimum humidity (%)Optimum temperature (°C)
Bathroom50 - 7021 - 23
Living room and study40 - 6020 - 23
Bedroom40 - 6016 - 18
Child's bedroom40 - 6020 - 23
Kitchen50 - 6018 - 20
Hallway40 - 6015 - 18
Cellar50 - 6510 - 15

Please note: A humidity of less than 30  percent should be avoided at all costs. A level below this is unhealthy and causes damage to materials such as wood.

Controlled mechanical ventilation in the bathroom

Photo: © Image Flow /

Controlled mechanical ventilation (CMV) makes it possible to optimally ventilate a bathroom without windows. But their use is also beneficial in a bathroom with a window. With this mechanical ventilation, a basic distinction is made between two versions:

  • Central ventilation
  • Decentralised ventilation

In a bathroom without windows, ventilation is actually mandatory. According to DIN 18017 and the guidelines of many federal states, windowless rooms must be ventilated by a mechanical system.

Since an intervention in the building fabric is necessary, central ventilation systems are mainly installed in new buildings. They consist of a ventilation unit and an air distribution system that can be integrated into the floor, wall or ceiling. Ventilation in the bathroom and other rooms is controlled via a central ventilation unit. Systems with integral heat exchangers have a clever secondary benefit: They can utilise the thermal energy of the extract air to heat the incoming fresh air. This relieves the load on the heating system and saves noticeably on costs. Viessmann central mechanical ventilation systems feature such heat recovery. For example, the Vitovent  200-C and Vitovent  300-C systems are suitable for living areas between 60  and 120  square metres (m²). If more living space is available, the Vitovent  300-W system ensures reliable ventilation of all rooms, including the bathroom.

Decentralised ventilation in the bathroom is more common, especially in older and existing buildings. This is because the ventilation units can be installed in individual rooms. Ventilation ducts are not needed for this. The bathroom has to be located on an external wall. In this case, only a wall opening and an electrical connection are required for the installation. Due to the straightforward installation, decentralised solutions are also ideal for modernisation projects. To guarantee good ventilation in the bathroom, there are various options.

  • Extract air fans: A bathroom vent with integrated extract air fan is the simplest solution to mechanically ventilate a bathroom. It creates negative pressure and transports humid air to the outside. To regulate the fan, it is linked to a timer and/or the light switch. A good alternative are devices with a humidity sensor. If the previously set humidity value is exceeded, the extract air fan switches on automatically. It should be noted that the air that is discharged to the outside via the bathroom fan must be replaced. In older buildings, this occurs through leaks in the building envelope. In newer buildings, air diffusers must be integrated into the external wall or overflow openings for this purpose, for example in the door. Shortening the door panel also ensures that sufficient air can flow in.
  • Extract and supply air fans: Extract air fans remove not only moisture but also heat to the outside along with the air. From an energy point of view, this is not efficient. Decentralised ventilation units with extract and supply air fans that work with heat recovery are better. These ensure good ventilation in the bathroom without unnecessarily consuming energy and driving up heating costs. If you want to retrofit a ventilation system in a bathroom, you can ventilate a floor area of up to 25  m² with the Vitovent  200-D, for example.

Decentralised and central mechanical ventilation can be combined. You can find out which solution is best suited to your project from a contractor. They will get an idea of the conditions on site and advise you individually.

Help with repair and maintenance of the ventilation system in the bathroom

With decentralised ventilation, many measures can be implemented yourself. If, for example, the system emits an unpleasant odour, deposits and contaminated filters are probably responsible. To remove or replace them, the cover must first be removed. Afterwards, the fan and cover are simply cleaned with a damp cloth. New filters from the manufacturer are available from specialist retailers.

If the ventilation system in the bathroom is running continuously, occupants can also initially try to identify the cause themselves. In case of a decentralised ventilation unit, a faulty or incorrectly adjusted overrun relay may be responsible. It should ensure that the bathroom fan switches off after a certain time. Under certain circumstances, it may be enough to readjust it. If the relay needs to be replaced or if there is another fault, it is recommended to contact an installer. They will replace the component professionally and carry out the adjustment. In the case of central ventilation systems, a contractor should always be brought in – both for repair and cleaning. This is because the entire duct system needs to be inspected

Ventilate the bathroom properly

It is advantageous if bathrooms can be ventilated via windows and a ventilation system. Moisture can escape quickly through an open window. At the latest after showering or having a bath, it should be opened fully for five to ten minutes. To prevent the humid air from spreading throughout the living area, it is advisable to close the bathroom door at the same time. Especially in winter, however, the window should not be left open for too long. Because the more heat that escapes through the window, the harder the heating has to work. To prevent this, it is better to turn the heating down while ventilating. In addition, moisture condenses especially on cold surfaces and can cause mould to form there in the medium to long term. For this reason, it is important to ensure temperatures between 21 and 23 degrees Celsius in the bathroom all year round.

A ventilation system with heat recovery helps to make ventilation in the bathroom even more efficient. This is because it ensures regular air exchanges even without open windows and the associated heat loss. At the same time, stale air is replaced by fresh, oxygen-rich air. Integral filters also retain dirt particles. Energy is saved, a pleasant room climate is created and mould formation is prevented.

More tips against mould

Besides proper ventilation and evenly high room temperatures, there are other measures to remedy mould. This includes wiping tiles, taps and the shower enclosure dry after showering and bathing. Shower curtains should be drawn so that they can dry better. It is also advisable to ensure that bathroom furniture is not placed too tight to the wall so that no moisture accumulates behind it.

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