Questions and answers
about the Mirror shaft®
General
What are good conditions for a Mirror shaft®?
- light wells that are as long and wide as possible, to ensure there is sufficient space for daylight to enter
- High basement windows, ideally with a sill height of approximately 1.60 m
- a window height that matches the width of the light well as closely as possible
- Good natural light conditions for the light well, for example due to a south-facing orientation and minimal shading
- no obstructing canopies, dense vegetation, or structural elements above the light well
- Brightly designed rooms in the basement, as light-colored ceilings, walls, and floors reflect daylight better
How deep can daylight be conducted down the shaft?
With the Heliobus® Spiegelschacht®, daylight can be directed downward even across multiple floors. Completed projects demonstrate that daylight can be directed up to four stories below ground level.
This makes the system suitable not only for traditional basements, but also for more challenging building situations where natural light needs to be directed deep into basements or interior spaces.
Are there standard shafts?
No, every Heliobus® Spiegelschacht® is custom-made. This is crucial because light wells, windows, and facade connections vary from building to building. Relevant factors include, among others:
- different window sizes and types, such as basement windows that open inward or outward
- different wall thicknesses, thermal insulation, and plaster systems
- different sill heights for basement windows
- varying depths, widths, and structural forms of the light wells
Custom manufacturing ensures that the Heliobus® Light Well® fits perfectly, directs natural light optimally into the room, and integrates seamlessly into the existing building structure.
What do I see when I look into the window?
The mirror module of the Heliobus® Spiegelschacht® opens in a funnel shape toward the basement window. This directs natural daylight into the room in a targeted manner and significantly improves the lighting conditions in the basement.
Under ideal structural conditions—for example, without a canopy, trees, or dense vegetation directly above the light well—it is even possible to have an unobstructed view of the sky. This allows you to watch the weather basement , making the space feel more open and more connected to the outside world.
The mirror’s geometry is designed to maximize the amount of natural light entering the space. As a result, the surroundings are not reflected exactly as they are, but are optically distorted in a manner similar to a kaleidoscope. This creates a unique interplay of light and space that makes the basement appear basement , more vibrant, and more upscale.
Can you see into the room from the outside?
Yes, depending on the type of glass covering and the lighting conditions, it is possible to see into the mirrored basement room from the outside. During the day, however, visibility is usually limited, as it is generally brighter outside than inside the room.
To see directly into the room, you would have to get very close to the cover and look in from the side—much like children who want to peek into an apartment or a car from the outside. In everyday life, therefore, the view inside is limited.
For more privacy, we recommend a simple solution, similar to what is commonly used with above-ground windows: a sheer white curtain or another discreet privacy screen inside the room. This can be closed as needed when more privacy is desired.
Effect
How much more daylight does the Mirror shaft® bring ?
The Heliobus® Spiegelschacht® brings up to 20 times more daylight into the basement. The daylight that falls on the top of the light well or grating is directed toward the basement window via the mirrored module with an efficiency of approximately 30 to 50%.
With a conventional light well, on average only a small portion of the available daylight enters the room directly and effectively—often just 2 to 10%. Thanks to the reflective geometry of the Heliobus® Spiegelschacht®, this available light is utilized much more efficiently.
Especially on overcast days, this can improve the amount of natural light in the basement by a factor of 10 to 20. The basement space appears brighter and more inviting, and the overall comfort level is significantly enhanced.
Does the Mirror shaft® work even when the sun is not shining?
Yes, the Heliobus® Spiegelschacht® works reliably even on cloudy days and in the rain. Even diffused daylight is captured by the mirrored module and directed into the basement.
The greatest effect is achieved when the system is exposed to direct sunlight. In such cases, the mirror system can direct light into the room with particular intensity—depending on the situation, even reaching areas further back in the basement.
The effect is similar to that of a standard window on an upper floor: even in the shade or in bad weather, the room remains bright, but when direct sunlight hits it, the effect is significantly more pronounced. In this way, the Heliobus® Spiegelschacht® provides more natural daylight and a more pleasant indoor atmosphere in a variety of weather conditions.
Do you get blinded in the sunshine at basement ?
Yes, that can happen. The effect is similar to that of a south-facing window: depending on the season, the position of the sun, and the building’s layout, direct sunlight may enter the room more intensely.
However, the mirrors in the Heliobus® Spiegelschacht® do not amplify sunlight or daylight; instead, they redirect it in a targeted manner. This allows for better use of the available natural light and directs it into the basement.
If direct sunlight is a problem in the room, curtains, roller shades, or blinds can help—just as they do for windows on upper floors. Many of our customers use a sheer white curtain. This keeps the room bright while pleasantly softening the direct sunlight.
Ventilation
Is it still possible to ventilate after installing a Mirror shaft®?
Yes, ventilation is still possible even when it rains. The Heliobus® Spiegelschacht® is designed with a sturdy steel frame that features integrated ventilation slots and laminated safety glass. This allows the basement to remain ventilated without the need to retain the traditional grating.
The airflow is reduced compared to an open grille, as the cross-sectional area through the laminated safety glass is smaller. However, the ventilation effect remains adequate and is roughly comparable to that of a casement window.
Depending on the building's layout, this approach can still ensure an effective supply of fresh air. Experience has shown that the air change rate typically ranges from about 10 to 20.
Cleaning and maintenance
How are the mirrors to be cleaned?
The mirrors in the Heliobus® Spiegelschacht® are easy to clean. Usually, cleaning them with water and a soft microfiber cloth is sufficient, just like cleaning a window or bathroom mirror.
For hard-to-reach areas, a telescoping window cleaner with an articulated arm can be helpful. Upon request, Heliobus® also offers a professional cleaning service.
Are the mirrors going blind?
Under normal conditions, the mirrors in the Heliobus® Mirror Shaft® retain their quality for many years. Their lifespan is comparable to that of high-quality bathroom mirrors or other mirrored surfaces, which remain clear and functional over the long term when properly maintained.
The key factor affecting durability is the humidity level in the light well. In rare cases, if humidity remains high over time or structural conditions are unfavorable, the edges of the mirrors may become damaged over time.
If a mirror is damaged or corroded around the edges, it can be easily replaced on site. If necessary, Heliobus® can also provide special protective measures to better shield the mirror surfaces from moisture.
Is the armoured glass scratch-resistant?
No, the glass cover of the Heliobus® Spiegelschacht® is not scratch-resistant. Although it is made of sturdy laminated safety glass, it should be treated with the same care as any high-quality glass surface.
For cleaning, we recommend soft microfiber cloths, water, or a suitable glass cleaner. Avoid using hard objects, metal tools, or sharp-edged snow shovels, as they can scratch the glass surface.
How intensive is the maintenance?
Just like windows, the mirror modules of the Heliobus® Spiegelschacht® should be cleaned regularly. How often this is necessary depends on the environment, weather conditions, and personal preferences regarding light and visibility.
Our experience shows that cleaning is usually done at the same time as regular window cleaning. As a rule, it is sufficient to clean the mirror modules and windows once or twice a year.
For gentle cleaning, we recommend using water, a soft microfiber cloth, or a suitable telescopic window cleaner for hard-to-reach areas.
Where does the surface water end up?
Rainwater and surface water can enter the existing light well through the ventilation slots to a limited extent. This is by design and is comparable to the previous situation with an open light well.
However, the water does not enter the mirror module of the Heliobus® Mirror Shaft®. As before, it is collected in the light well via the existing well floor, where it either seeps away or is drained off through the existing drainage system.
It is therefore important that the light well has a properly functioning drainage system and that rainwater can drain away freely.
Is condensation forming in the mirror module?
Yes, condensation can form in the Heliobus® Spiegelschacht® area. Whether this occurs—and to what extent—depends primarily on the structural condition of the existing light well.
High moisture levels caused by rainwater, runoff from slopes, or inadequate drainage can promote the formation of condensation. That is why it is particularly important to ensure that the light well has a properly functioning drainage system.
As a rule, it is primarily the flat laminated safety glass cover that is affected. The mirror surfaces themselves rarely develop condensation—for example, when humidity is very high in wet rooms, saunas, or showers, especially immediately after ventilation.
If necessary, Heliobus® can evaluate technical options such as heatable laminated safety glass to reduce condensation and maintain light transmission over the long term.
Is the mirror module protected from dirt from the street?
The mirror module of the Heliobus® Spiegelschacht® is protected from above by a laminated safety glass cover. This ensures that the mirrors cannot be damaged directly from above under normal use.
Because the system is designed to be open to the air and allows for natural ventilation of the light well, dust may accumulate on the mirror surfaces over time. This is normal and can be easily remedied with regular, gentle cleaning.
To ensure that the mirrors continue to provide good lighting, we recommend cleaning them once or twice a year along with your regular window cleaning, depending on the environment and the level of dirt.
Condensate
Helpful hints on condensation formation
With Heliobus® Mirror Shafts®, the laminated safety glass above the mirror module may occasionally fog up—usually during the transitional period in the fall or when there are significant temperature changes. This condensation is a natural physical process and is generally no cause for concern.
The condensation usually evaporates on its own and generally has no negative impact on the performance or service life of the Spiegelschacht® system. The lighting effect may be slightly reduced during this time, but it will stabilize again once the temperature and humidity levels return to normal.
A light well is located directly against the building and is partially surrounded by soil. During colder seasons, the temperature inside the well can therefore be higher than the outside temperature. When the warmer, more humid air from the well comes into contact with the cold glass, condensation can form.
Condensation is particularly likely to occur due to heavy rain, runoff from slopes, insufficient drainage, or restricted drainage within the light well. A sudden drop in temperature can also increase the formation of condensation, because the well cools more slowly than the surrounding air and the glass surface.
It is not always possible to reliably determine in advance whether a particular light well is prone to condensation. Factors such as drainage characteristics, soil composition, soil moisture retention, hydrostatic pressure, and local weather conditions play a significant role in this regard.
It is therefore important that the existing light well has a properly functioning drainage system and that water can drain away freely. In special structural situations, Heliobus® can evaluate additional technical options to reduce condensation and ensure long-term light transmission.
Solutions to minimise condensate
Heatable laminated safety glass with automatic control
To reduce or prevent condensation, heatable laminated safety glass can be used instead of standard laminated safety glass. When combined with an automatic electrical control system, the glass surface is heated as needed, so that less moisture condenses on the cover.
This solution is particularly suitable for light wells where structural conditions, high humidity, or significant temperature fluctuations can lead to increased condensation. For more information, please refer to the product specifications.
Concreting the shaft floor
To minimize condensation caused by rising moisture from the shaft floor, we recommend finishing the shaft floor with a concrete slab and a siphoned floor drain.
This allows moisture to be wicked away in a more controlled manner while reducing moisture rising from the ground. This structural measure helps maintain a more stable climate in the light well and can also reduce the formation of condensation. For more information, see the section on structural measures.
Security
When is slip resistance necessary?
Anti-slip treatment is recommended whenever the manhole cover of the Heliobus® Spiegelschacht® is located in an area with regular foot traffic—for example, on a patio, at a building entrance, on a sidewalk, or in a passageway.
In public or high-traffic areas, a slip-resistant finish is particularly important to enhance safety in wet or damp conditions or when weather conditions change.
Why does the slip resistance have stripes?
The striped anti-slip surface of the Heliobus® manhole cover combines safety with high light transmission. The arrangement of the stripes ensures that as much natural daylight as possible enters the room.
At the same time, the view to the outside remains largely unobstructed, even though it may be slightly limited by the anti-slip coating. This makes the glass surface safer to walk on without unnecessarily compromising the lighting effect or the connection to the outside world.
The design of the slip-resistant surface is based on test results and safety requirements, including those set forth by the Swiss Council for Accident Prevention (BFU).
Is the Mirror shaft® burglar-proof?
We cannot guarantee complete protection against break-ins. However, the Heliobus® Spiegelschacht® is designed in such a way that the mirror module cannot simply be lifted out of the light well as a whole.
As a result, the system provides significant burglary resistance and offers greater protection compared to many conventional light well covers. The combination of a mirror module, a sturdy cover, and structural integration further hinders unauthorized entry.
For covers without a mirror module, an additional anti-theft device is recommended. Depending on the specific installation conditions, Heliobus® can evaluate suitable security options and provide customized solutions.
Can the Heliobus® shaft cover be walked on?
Yes, the glass cover of the Heliobus® Spiegelschacht® is made of sturdy laminated safety glass (LSG) and is walkable when used properly. When dry, the cover can be walked on safely.
The structural design is tailored to each specific project and complies with applicable Swiss standards as well as the recommendations of the Swiss Society of Engineers and Architects (SIA). This ensures that the manhole cover is suitable for the specific structural conditions and intended use.
Vehicle Accessibility: In Switzerland, a reinforced version is available as an option, which may allow limited vehicle access for vehicles weighing up to 3.5 tons. However, the specific design must always be evaluated on a case-by-case basis.
Unrestricted trafficability requires additional structural and design analyses. In countries outside Switzerland, specific certifications, tests, or case-by-case assessments may be required, depending on local regulations.
Where does the surface water end up?
Rainwater and surface water can enter the existing light well through the ventilation slots to a limited extent. This is by design and essentially corresponds to the previous situation of an open light well.
However, the water does not enter the mirror module of the Heliobus® Mirror Shaft®. As before, it is collected in the light well via the existing well floor, where it either seeps away or is drained off through the existing drainage system.
It is therefore important that the light well has a properly functioning drainage system and that rainwater can drain away freely.
Is condensation forming in the mirror module?
Yes, condensation can form in the Heliobus® Spiegelschacht® area. Whether this occurs—and to what extent—depends primarily on the structural condition of the existing light well.
High moisture levels caused by rainwater, runoff from slopes, or inadequate drainage can promote the formation of condensation. That is why it is particularly important to ensure that the light well has a properly functioning drainage system.
As a rule, it is primarily the flat laminated safety glass cover that is affected. The mirror surfaces themselves rarely develop condensation—for example, when humidity is very high in wet rooms, saunas, or showers, especially immediately after ventilation.
If necessary, Heliobus® can evaluate technical options such as heatable laminated safety glass to reduce condensation and maintain light transmission over the long term.
Is the mirror module protected from dirt from the street?
The mirror module of the Heliobus® Spiegelschacht® is protected from above by a laminated safety glass cover. This protects the mirrors from direct impact from above during normal use.
Because the system is designed to be open to the air and allows for natural ventilation of the light well, dust may accumulate on the mirror surfaces over time. This is normal and can be easily remedied with regular, gentle cleaning.
To ensure that the mirrors continue to provide good lighting, we recommend cleaning them once or twice a year along with your regular window cleaning, depending on the environment and the level of dirt.
