Questions and answers
about the Mirror Shaft
General
What are good conditions for a Mirror Shaft?
- Long and wide light wells
- High cellar windows in the basement, optimally with a parapet height of 1.60 m
- Window height similar to shaft width
- Good daylight conditions for the light shaft: south-facing and no canopies or plants above the light shaft
- Brightly coloured rooms in the basement
How deep can daylight be conducted down the shaft?
Daylight can be directed down several storeys in the shaft. Projects carried out up to 4 storeys below ground level show that this is possible without any problems.
Are there standard shafts?
No, each Mirror Shaft is custom made. Reasons for this are:
- Different windows, hinged on the outside on the inside
- Different wall thicknesses, thermal insulation, plaster thicknesses
- Different sill heights for the windows
- Different shaft depths
What do I see when I look into the window?
The mirror module opens towards the basement window.
In an optimal situation (no canopy, trees or plants directly above the light well), you get a clear view of the sky and can follow the weather from basement . Due to the mirror geometry for maximum daylight incidence, the surroundings are not mirrored one-to-one, but are blended similar to a kaleidoscope.
Can you see into the room from the outside?
Yes, you can see into the mirrored basement room from the outside. During the day, when it is always brighter outside than inside, you can only see inside to a limited extent. To do so, you would have to hold your hands to the side of your face, just like children do when they want to look into their flat or car from the outside. Many of our clients solve this problem with a fine white curtain, just like in the overground area. This can then be drawn when privacy is desired.
Effect
How much more daylight does the Mirror Shaft bring ?
The Mirror Shaft brings up to 20 times more daylight into the basement room. The daylight falling on the light shaft (grating) is directed to the basement window with an efficiency of approx. 30 to 50%. On average, only about 2 to 10% of the daylight falls at right angles into the room at the basement window. This results in a 10 to 20-fold improvement in value when the sky is overcast.
Does the Mirror Shaft work even when the sun is not shining?
Yes, the system also works without problems under overcast skies and in rain. However, the effect is much greater in direct sunlight and can often be mirrored to the back of the room due to the mirror system. It behaves the same as on the upper floor - here, too, it is bright if the windows are in the shade or if there is bad weather, and all the brighter if the sun shines directly into the windows.
Do you get blinded in the sunshine at basement ?
Yes, that can happen. It behaves similarly to a south-facing window when the sun is shining, which lets in more sunshine depending on the season and the position of the sun. However, the mirrors only redirect the sunlight and daylight, but do not intensify it. If the sun interferes, curtains, roller blinds or venetian blinds help, as with windows on the upper floor. Many of our customers solve this problem with a fine white curtain so that the room remains bright but the sun's rays are softened.
Ventilation
Is it still possible to ventilate after installing a mirror shaft?
Yes, due to the technical construction of the steel frame with ventilation slits and laminated safety glass inserted into it, it is possible to ventilate the room even when it rains. However, the amount of air is less than with a grille. The cross-section is reduced by the laminated safety glass. The ventilation volume is roughly comparable to a top-hung window; this still results in an air exchange rate of 10 to 20.
Cleaning and maintenance
How are the mirrors to be cleaned?
Are the mirrors going blind?
Normally, mirrors retain their quality throughout their entire service life. It is similar to bathroom mirrors, which start to become cloudy after 20 years. However, the moisture in the light well is largely responsible for this. In exceptional cases, the mirrors are already corroded at the edges. However, these can be easily replaced on site and, if necessary, additionally provided with a special protection.
Is the armoured glass scratch-resistant?
No, the glass cover is not scratch-resistant.
How intensive is the maintenance?
Windows generally need to be cleaned. The intensity depends largely on the needs of the user. Our experience shows that the mirror modules are cleaned together with the windows. 1 to 2 times per year.
Where does the surface water end up?
Surface water, generally rainwater, enters the light well through the ventilation slots, but not into the mirror module. It seeps into the light well as before.
Is condensation forming in the mirror module?
Yes, condensation can occur.
This is primarily dependent on the structural situation of the shaft. Large amounts of water entering the shaft due to rain, slope water or poor infiltration influence the formation of condensate. Usually only the flat laminated safety glass cover is affected. Mirror surfaces very rarely condense, for example in damp rooms, saunas, showers, immediately after airing out very high humidity.
Is the mirror module protected from dirt from the street?
The mirror module is protected against direct impact from above via the laminated safety glass. Mirrors cannot be damaged from above.
However, the mirror can get dusty because the system is open to the air and has a natural ventilation system.
Condensate
Helpful hints on condensation formation
Time and again - mostly in the transitional period in autumn - it can happen with Heliobus mirror shafts that the armored glass above the mirror module temporarily fogs up. This is a natural process and no reason for concern. The condensate evaporates again and normally has no negative effect on the Mirror Shaft.
Since a cellar shaft is mounted on the house in the ground, the temperature in the shaft is higher than the outside temperature in cold seasons. If the air in the shaft then hits the cold glass, condensation may form there. Light wells that are exposed to heavy rain and/or have insufficient infiltration promote the formation of condensation. Another scenario is a drop in temperature, whereby the shaft only cools down gradually, while the ambient and thus also the glass temperature have already dropped considerably. This makes the formation of condensation all the more likely.
Condensation in reflector shafts is therefore a natural, physically conditioned phenomenon that can occur especially in the cold season. Due to a wide variety of factors such as seepage behaviour in the shaft, subsoil conditions, wet storage capacity of the soil, slope water pressure, etc., it is unfortunately not possible to say in advance which shaft might be affected.
Solutions to minimise condensate
Heatable laminated safety glass with automatic control
In order to prevent condensation, a heatable laminated safety glass with corresponding electrical control can be used instead of the normal laminated safety glass. You can find further information under Product technical measures
Concreting the shaft floor
To minimise the formation of condensation in the event of rising damp from the shaft floor, we recommend closing off the shaft floor with a concreted floor and a siphoned floor drain. You can find more information under Structural measures.
Security
When is slip resistance necessary?
Why does the slip resistance have stripes?
On the one hand, as much daylight as possible enters the room through the strips. On the other hand, the view to the outside can be maintained, albeit somewhat limited.
The dimensions are based on the test results, Federal Office for Accident Prevention (BfU).
Is the Mirror Shaft burglar-proof?
We do not guarantee general burglar resistance. The shape of the mirror module prevents the whole system from being lifted out of the shaft. Our system is thus highly burglar-resistant; far more so than conventional "burglar-proofing".
A cover without a mirror module requires an additional burglar alarm.
Can the Heliobus® shaft cover be walked on?
Yes, Heliobus® uses laminated safety glass (LSG), which can be walked on safely when dry.
The structural design is carried out according to Swiss standards, based on the recommendation of the Swiss Association of Engineers and Architects.
Trafficability:
In Switzerland, an option is available that allows limited trafficability for vehicles up to 3.5 tonnes.
Unrestricted trafficability requires object-specific clarifications.
In some cases, navigability in countries outside of Switzerland is only possible with special tests in individual cases.
Where does the surface water end up?
Surface water, generally rainwater, enters the light well through the ventilation slots, but not into the mirror module. It seeps into the light well as before.
Is condensation forming in the mirror module?
Yes, condensation can occur.
This is primarily dependent on the structural situation of the shaft. Large amounts of water entering the shaft due to rain, slope water or poor infiltration influence the formation of condensate. Usually only the flat laminated safety glass cover is affected. Mirror surfaces very rarely condense, for example in damp rooms, saunas, showers, immediately after airing out very high humidity.
Is the mirror module protected from dirt from the street?
The mirror module is protected against direct impact from above via the laminated safety glass. Mirrors cannot be damaged from above.
However, the mirror can get dusty because the system is open to the air and has a natural ventilation system.
