Bathroom without a window: ventilate properly, create a bright design
Bathrooms without windows are common, especially in flats and apartment buildings. They have two main drawbacks: the humid air cannot simply escape through a window, and there is no natural daylight.
This explains how the ventilation should work, how to recognise problems, and how to make the bathroom appear bright and welcoming nonetheless.
Professionally reviewed by Julien El-Bahy, bazuba headquartersAs of: 27 September 2026
In short
Without a window, the bathroom requires an exhaust fan to remove humid air to the outside, and an opening to allow fresh air to flow in. Bright lighting and light-coloured surfaces ensure it does not feel like a chamber.
Exhaust air60 m³/hReference value according to DIN 18017-3 for a bathroom in Germany; for continuous operation, 40 m³/hOn ventilation
Humidity40 to 60%Quickly return to this level after showering; a hygrometer displays the valuePrevent mould
Lighting: Multiple light sources, good colour rendering, and light-coloured walls make the biggest difference. Learn more
Reference values simplified according to DIN 18017-3 (Germany) and OIB Guideline 3 (Austria). Installation and modifications to ventilation should be carried out by a specialist company. As of: 27 September 2026. Professionally reviewed by Julien El-Bahy (bazuba headquarters).
How to ventilate a bathroom without a window properly
Without a window, an exhaust fan takes care of ventilation. It extracts the humid air and directs it outside via a duct or pipe. For it to work, air from the flat must flow in, usually through a gap under the door.
Fan
How it works
Suitable for
With run-on timer
starts with the light and continues running for a few minutes after switching off
short-term use, easy retrofitting
With humidity sensor
switches on as soon as humidity rises, and runs until it drops again
Bathrooms where showers are used frequently
Continuous operation with two levels
runs quietly at low power all the time and switches to higher power when needed
internal bathrooms, new builds and renovations
Central system
several bathrooms are connected to a shared fan, often in apartment buildings
Rental flats, changes only with property management approval
What the regulations require
Germany: DIN 18017-3 regulates the ventilation of bathrooms without external windows. As a guideline, it specifies around 60 m³ of exhaust air per hour for a bathroom if the fan can be switched off and has a run-on function, or 40 m³ per hour if it runs for at least 12 hours a day. For a WC, the requirement is half. Each room also needs an air supply opening with a free cross-section of 150 cm² that cannot be closed, such as a gap under the door or a grille.
Austria: According to point 10.1.1 of OIB Guideline 3, sanitary rooms must be adequately ventilated, either naturally or mechanically. Without a window, this is usually done by an exhaust fan; a fan that draws air in from adjacent rooms via ventilation or door slots also counts as mechanical ventilation. The guideline is implemented through the building regulations of the federal states.
How to tell if the ventilation is insufficient
The mirror stays fogged up long after showering.
Drops form on the ceiling and walls.
There is a musty smell, towels dry poorly.
Dark spots appear in joints and corners.
Simple test: Hold a sheet of toilet paper in front of the grille while the fan is running. If it is sucked in, the fan is working. If it barely moves, the grille, filter or duct is often dirty, or there is no air supply.
Replace or retrofit the fan
An old, noisy fan can usually be replaced with a quiet model with a run-on function or humidity sensor. If there is no fan yet, a route to the outside is needed, such as an existing duct or a core drill hole. This work should be carried out by an electrical or ventilation specialist. In rented flats and with central systems, consult your landlord or property management beforehand.
Preventing moisture and mould
Let the fan run: after showering, until the mirror is clear. Keep the door closed; air will flow in through the gap.
Remove water: A squeegee for the shower screen and tiles removes much of the moisture before it evaporates.
Measure humidity: A hygrometer shows whether the humidity drops back to around 40 to 60% after showering.
Keep the room warm: Moisture condenses on cold walls. The bathroom should not cool down.
Dry towels: on a heated towel rail or outside the bathroom.
Keep an eye on joints: Dark silicone joints are often the first sign of mould. How to replace them is explained in the guide Renew silicone joints.
If mould is already present, you can remove small areas yourself. Find out how to do this and when to call in professionals in our guide Remove mould in the bathroom. Fewer joints mean fewer surfaces for mould: A seamless wall coating can be applied directly onto the old tiles without demolition, and with the grout renovation we renew the joints and treat any mould at the same time.
Bright walls without demolition?Brighten tiles with a coating or opt for seamless walls, usually completed within a few days. Free inspection in Germany and Austria.
Without daylight, artificial lighting does everything. Therefore, plan for several light sources instead of a single ceiling light:
General lighting on the ceiling: even and glare-free, so the whole room is uniformly bright.
Lighting at the mirror: from the front or side, so there are no shadows on your face when shaving or applying make-up.
Mood lighting: for example, LED strips behind the mirror or in a niche, ideally dimmable.
Light colour: warm white for the evening, neutral white for the mirror lighting. Very cold „daylight“ can quickly make a bathroom feel uncomfortable.
Colour rendering: Luminaires with a Ra value of 90 or more show skin and colours naturally.
Which lights are permitted in each protection zone and how bright they should be is explained in the guide Bathroom lighting.
How to make the bathroom appear brighter and larger
Bright surfaces: White, cream, light grey or delicate pastel shades reflect the light. Dark tiles do not have to be removed: We can renovate them without demolition with a light-coloured coating, available in over 250 colours.
Calm walls: Many joints and small tiles create a restless look. Smooth surfaces seamless walls make the room appear larger.
Large mirror: It visually doubles the light, ideally spanning the entire width of the washbasin.
Glass instead of a curtain: A clear shower screen does not divide the room.
Minimal clutter: Closed cabinets and niches keep the view clear.
Greenery: Plants will only grow without daylight if you use a plant lamp. Which types are suitable can be found in the guide Plants for the bathroom.
If your bathroom is also small, you will find more ideas in the guide Small bathroom.
Include in your bathroom renovation planning
If the bathroom is being renovated anyway, it is worthwhile to consider ventilation and lighting at the same time: a quiet fan with a humidity sensor, an air transfer opening in the door, a mirror with lighting, and bright surfaces.
bazuba renovates bathrooms without demolition, usually within a few days. For electrical and installation work such as fans and lights, we cooperate with partner companies from the electrical and installation trades, but you still have a single point of contact. Learn more at Installation work.
Frequently asked questions about bathrooms without windows
Yes, if it is effectively ventilated. In Germany, DIN 18017-3 describes how bathrooms without external windows must be ventilated. In Austria, OIB Guideline 3 requires that sanitary rooms are adequately ventilated; without a window, an exhaust fan with air supply via ventilation or door slots is sufficient.
Let the fan run after showering until the mirror is clear again, and keep the door closed during this time. Fresh air enters through the gap under the door or a grille. This opening must not be blocked or sealed.
Until the mirror is clear and the humidity is back to around 40 to 60 percent, often 15 to 30 minutes. A fan with a humidity sensor regulates this automatically.
Common reasons: The fan is too weak or dirty, it runs for too short a time, or there is no air supply opening because the door is tightly sealed at the bottom. Cold walls and dark, old silicone joints also encourage mould.
With several light sources, a large mirror and bright surfaces. Dark tiles can be coated in a light shade without demolition, and seamless walls make the room appear calmer and larger.
Warm white for a pleasant general atmosphere, neutral white for the mirror lighting. Look for good colour rendering with a Ra value of 90 or more. Dimmable lights can be adjusted to suit the time of day.
In the long term, not without help, as plants need light. With a plant lamp that shines for a few hours each day, undemanding species such as ZZ plant or cast iron plant will survive. Alternatively, a good artificial plant is an option.
Generally only with the landlord’s consent, as this usually involves drilling or connecting to a shaft. If there are central ventilation systems in the building, you should not intervene yourself, but contact the property management.
More guides for the bathroom
Plants for the bathroom
Twelve plants that thrive in the bathroom, and which ones work without a window.
„On the recommendation of a friend, we got in touch with bazuba Rostock for our bathroom renovation. Since it’s a rental apartment, there were quite a few things to consider with the landlord/owner’s approval, but we were able to implement many individual wishes at our own expense. The initial contact was very pleasant, and first, an assessment was made, and of course, the initial ideas and wishes for the project were recorded. The basic task was to transform the over 20-year-old tiled bathroom with an old bathtub into a modern seamless bathroom with a walk-in rain shower. The company’s showroom had quite a few displays, where we could get our first personal impressions. Then we put together the rest from the catalogs, and we also relied on the advice and recommendations of the boss there, who contributed some great ideas. Then we received an offer with a 3D visualization of the finished bathroom. This allowed us to work very well together with the owner and bazuba on the details and arrive at a final result. The correspondence between bazuba and the owner also went very smoothly, and we were very well informed about delivery times, construction times, and the entire process up to the finished bathroom. We helped set up the construction site by covering the floor and cabinets, and the company’s employees were very friendly and informative about the work steps. We hardly had to ask anything because every morning we were informed about what would happen that day until quitting time. The announced construction time was even undercut by 2 days because everything really fit together, and the trades worked hand in hand. The handover and the finished result, including explanations of all the components, care instructions, and warranties, worked wonderfully and were presented to us very transparently. All in all, we are very satisfied with the result, and for the small space available, it almost feels like being in a good hotel when you step into the shower in the morning 😉 I can definitely recommend bazuba Rostock and am happy to show some before-and-after pictures. It’s not decorated or furnished yet, but it’s about the raw result."
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Marco S.
Rostock ·
Google
“
„Complete renovation of bathroom and WC — After weeks of searching online for a company that could take on our project (complete renovation of bathroom and WC), we came across bazuba. Although all customer reviews pointed to an outstanding company, we still felt the need to visit the company location in Guntramsdorf in person first. But from that moment on, it was clear to us that only this company was suitable for our project. The exceptionally warm, competent, polite, friendly, and patient team immediately convinced us. From then on, everything went very quickly. We arranged an inspection appointment with Mr. Weninger. The inspection, consultation, measuring, and addressing special requests all took place in a very friendly and relaxed atmosphere. The gentleman was very patient and really took a lot of time for us, only leaving once even the smallest detail was clarified. After the very detailed offer and placing the order, the renovation work began punctually on the agreed date. From here on, I have to keep it short, otherwise I would need two more pages. ALL involved, whether subcontractors or the truly outstanding bazuba specialists, carried out their tasks so competently, punctually, cleanly, almost dust-free, quickly, friendly, politely, courteously, professionally, precisely, and expertly that words almost fail me. The continuous support and (after)care of my project are also worth highlighting. After completing the very extensive work, I now have two real gems (bathroom and WC), and I find myself spending much more time there than really necessary. The conclusion of a highly satisfied and enthusiastic customer: the best 10-star company I have ever dealt with. I have recommended and will always recommend bazuba."
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werner.lissa
Guntramsdorf ·
Herold
“
„Everything just fits perfectly! :o) We had bazuba renovate our roughly 50-year-old bathroom and the equally old toilet, and also modernize the shower in the second bathroom. From the very first (phone) contact, we had a good feeling. Bathroom planner Raffael came to our home and went through the various steps with us, giving us good advice and showing a lot of patience. We were also able to talk openly about the price, and in the end he gave us an offer we were very happy with. We had also gotten quotes from competitors, which were noticeably more expensive—we’re talking +50% or more. The implementation then went perfectly. First came the demolition team, then the electricians, the plasterers/floor layers, and finally the installation team. Overall, the work took almost three weeks, but that was agreed on beforehand and so was fine. All the workers always arrived as scheduled, were very friendly, explained a lot to us, and did a great job. We were also very grateful that they pointed out some possible/necessary improvements. Our spontaneous change requests were welcomed and carried out. At the same time, planner Raffael and project manager Anel were always reachable and responded quickly to our questions. The result speaks for itself: from old-fashioned, dark rooms with very worn installations, we now have bright, modern wet rooms that you enjoy entering again. The planning concept was implemented 100% in reality and at what we think is a really fair price. No trouble with the craftsmen at all—in fact, it was a pleasure, and we can warmly recommend the entire bazuba team."
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Hans G.
Guntramsdorf ·
Google
“
„Due to water damage in 2023 and subsequent repair work by a specialist company, we were then looking for a company to get our bathroom back in shape. This turned out to be not so easy; local companies either declined due to lack of time or didn’t show up despite appointments. Through internet research, we came across bazuba in Karlsruhe. We quickly had a first appointment with Mr. Glutsch. He arrived on time at our place, listened to our ideas about remodeling the bathroom, and shared his professional knowledge and comments. He took measurements, made notes, and promised to prepare an offer, which arrived in the shortest time. Due to several work appointments with bazuba, he already told us in advance that the work would be delayed and we should expect a date in March/April. But that didn’t matter to us in the end, since thanks to the preliminary work of the renovation company, we could still use our 30-year-old bathroom. When choosing the ceramics and the walk-in shower, we were with Mr. Glutsch at C.Ufer in KA (top advice!). In April, the work started on our partially renovated bathroom. After about 2 weeks, we could fully use our new bathroom; for the shower enclosure, we had to make do with a temporary solution, which was replaced after 5 weeks by a glass partition from Kermi. All in all, we were very impressed by the support and advice from bazuba (special thanks to Mr. Glutsch). A big compliment to the two skilled workers responsible for the work!! Without a doubt, 5 stars for bazuba."
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PG
Peter G.
Karlsruhe ·
Google
“
„Good decision! — We chose BAZUBA because of a report on an online portal... and we have no regrets! Our wishes were discussed and planned in the showroom with an incredible amount of patience. Even changes and special requests before the renovation started were implemented quickly and easily. The entire construction team also deserves mention – everyone was without exception polite and friendly. I especially want to mention Mr. Robert, who brightened every one of our site visits with his good mood. In hindsight, we can now list the following reasons why we recommend BAZUBA to everyone: 1.) The price – All other quotes were about 25% higher than BAZUBA’s. 2.) The team – As already mentioned, patience and friendliness are top priorities here. 3.) The planning – None of our wishes were considered impossible. Even special requests were gladly fulfilled. 4.) The working time – A conventional renovation would have taken at least 4 weeks and the whole house would have been dusty. BAZUBA finished on schedule in 2 weeks. 5.) The quality – Nothing wobbles, nothing is scratched. The bathtub looks like new. The walls are flawless. Every joint fits perfectly. 6.) The look – We chose a seamless bathroom. Compared to tiles, our bathroom now feels much friendlier and warmer. 7.) The warranty! All in all, we are satisfied customers and would have our bathroom renovated by BAZUBA again anytime."
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Christopher
Guntramsdorf ·
Herold
“
„Perfect! Absolutely recommend. — Tub out and shower in! From start to finish, we can only give the highest praise. The consultant, Mr. Raffael Weninger, gave us excellent advice at home. He took our needs into account and came up with a perfect plan for us with his great ideas. The craftsmen also deserve the highest praise. They were extremely careful to avoid dust and dirt, which is not easy with this kind of work. The first two days, two careful installers took on their responsible tasks. After all, all newly laid water pipes and drains have to be completely sealed. The third and fourth days belonged to the quick gentlemen Jànos and Gàbor, who were able to complete this partial renovation on time — without taking a break! It must be said that all "our" four craftsmen are extremely friendly and hardworking. Otherwise, our project would not have been completed perfectly in this relatively short time. On the third day, the company owner visited us, checked on the progress, and asked about our satisfaction so far. That builds trust. Now we enjoy our new shower pleasure every day! We gladly recommend this company with its great employees. Warm regards! Christian & Sylvia Karner"
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Christian K.
Guntramsdorf ·
Herold
“
„NEW BATHROOM For about 3 weeks now, we have been proud owners of a seamless bathroom and toilet. The first team from bazuba arrived on time and very punctual, professionally covering everything from the front door up to the bathroom, including the stairs, and began dismantling the old sanitary fixtures, disposing of everything no longer needed. From then on, things moved quickly every day. Congratulations to your employees. Everyone was extremely friendly, polite, and really hardworking. No matter what was being done, we were always asked if everything was okay or if we had other wishes. The new walk-in shower is truly a dream, the walls seamless and so beautifully bright, and the floor really very nice and easy to maintain. The toilet was done in the same style. Simply beautiful. I wanted to wait with the review until I got used to the new bathroom. Every morning, when I enter our beautiful bathroom, I am very happy. No matter which team was on site, all employees did professional work. We will always remember bazuba from Guntramsdorf fondly and will gladly recommend them. Thank you very much for everything. Best regards, Renate P."
We will inspect your bathroom free of charge and provide a fixed price after the visit. Prefer to call? Free from Germany at 0800 90 44 2000, from Austria on 0800 66 55 36.
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