Bathroom Venting - Opportunities at a Glance

Bathroom Venting - Opportunities at a Glance

Ventilating bathrooms is important. Due to the high level of humidity in the bathroom, there is a high risk of mold formation.

Why venting is important

Bathrooms are generally small rooms where large amounts of water vapor are generated during bathing or showering. The scale can easily be illustrated by a calculation.

A bath measuring 2 meters by 4 meters and 2.50 meters high has a volume of 20 cubic meters. A shower bath of 15 minutes releases 650 grams of water. That's 32.5 grams per cubic meter.

At a room temperature of 20 degrees, the air can hold a maximum of 17.3 grams of water, so the air in a bath of this size can contain a maximum of 346 grams of water vapor. After each shower, 300 grams of water condenses in the room.

This can be prevented if the water, saturated with steam, immediately flows into the open air. Windows are often not sufficient for sole ventilation.

Problems when venting bathrooms

DIN 18017 Parts 1 and 3 prescribe an hourly room air change for bathrooms and toilets without external windows. In a bath of this size, 20 cubic meters of air must be allowed to escape within 60 minutes. This is only possible with large window openings when the window is completely open.

For centralized ventilation systems, the standard requires the fan to transport 60 cubic meters per hour if there are no or too small windows it can be switched off. If the bath fan runs constantly, 40 cubic meters per hour suffice. To make sure that the humid air escapes quickly, experts recommend installing fans that extract five times the air volume of the room in one hour.

In today's well-insulated living spaces, suction creates a negative pressure, since not enough air flows in. For this reason, an additional opening of 150 square centimeters in size is required, through which fresh air enters.

The fresh air can flow directly into the bathroom or into an adjacent room, provided the door of the bath has a correspondingly large ventilation slot.

Useful in that the cold outside air flows into an unheated room and from there into the bathroom. In this way, the supply of dry air is guaranteed. The exact planning of the supply and exhaust air belongs in the hands of a specialist. Errors have a fatal effect, as moist warm air gets into cool rooms, which leads to mold.

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Possibilities of ventilation

The ventilation can be done centrally via a shaft. The installation is not possible later. Who takes this into account when building a house, has two alternatives. A large fan in the shaft or in each bath a small fan. Such a system makes house construction insignificantly more expensive.

Since warm air rises, it makes sense to divert it there. For suspended ceilings, suction on the ceiling and transport of the exhaust air via a pipe system to the next outer wall is possible. The fan should aspirate the air directly over the shower or the tub, so it does not spread in the room.

However, the piping may not be longer than three meters. The tube fans required for this purpose cost between 50 and 100 euros. For the exhaust duct, the grille and a non-return device additional amounts of 80 to 200 Euro are required.

Wall fans can be installed in any bathroom with an external wall. The installation is expediently just below the ceiling. Vacuuming over the shower or bath is usually not possible.

The fans cost between € 20 and € 50, and the pipes and flaps for the exterior wall will continue to cost € 50 to € 100.

Pairing with the light switch and a sensor that automatically activates the fan above a certain humidity level hires. Devices with this sensor technology typically cost around 20 euros more than simple ones without these sensors.

Professional or home improvement

Wall mounting a bath fan is no problem for a home improvement, provided the door of the bath becomes a ventilated unheated one Room goes. It is safer when a ventilation specialist looks at the premises. If a complex system with several extraction points is planned, an expert should always be present.

The masonry breakthroughs to lay the exhaust pipes can be done by a trained DIY enthusiast. If you do not have a strong drill, you need a hammer, a chisel and a lot of muscle power.

Installation is tricky with insulated masonry, since faults lead to cold spots. This task is better carried out by a specialist

The connection of the fans is always in the hands of a specialist company for ventilation systems or at least that of an electrician. The fans must be connected to the existing light pipe, they do not have a plug.

The installation costs between 200 and 300 euros. These are approximate values, the costs may be lower or higher depending on the system or local conditions.

Connecting the electricity costs around 50 Euro.

Advantages and disadvantages of the systems

Extracting the air through one Opening in the ceiling is optimal because the steam is not distributed in the room. The disadvantage is that there must be enough space above the ceiling to lay an exhaust pipe.

Wall systems are easy to install, but they do not ventilate so effectively.

Overview of the bath fan


Advantages / disadvantages


Central exhaust duct to roof

Only possible with new build

Very different in individual cases

Ceiling fan with exhaust duct

Advantage: Vacuum optimally

Disadvantages: There must be at least 50 centimeters of space be available above the ceiling

Cable may not be longer than three meters

Between 130 and 300 euros without installation

Wall fan

Advantage: Can be installed in any exterior wall

Disadvantage: Does not vacuum optimally

Between 70 and 150 euros without installation

Important: Although a built-in ventilator is important for ventilating a bathroom, tenants are not allowed to install it without the landlord's permission.

In principle, these installations are always profitable, improper installation or an unfavorable air supply can a to cause problems. It therefore makes sense to seek advice from a specialist.

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Video: Dryer Vent project|