Many customers want balustrades with glass fillings on their balconies. Most of them want a “frosted glass” look. At first sight this is an unspectacular thing. In detail it is exactly the opposite.
The installation regulations for glass as a structurally loadable component are regulated and defined in detail. In addition, there are also design and practical consequences that need to be considered and to which we would like to draw attention.
First of all, an explanation of two recurring terms
Toughened safety glass ESG
A panel of tempered safety glass is a panel of glass that has undergone a special thermal treatment. Due to this thermal treatment, this glass achieves high impact and shock resistance. That is why it is called safe. Because it doesn’t break so quickly and therefore you can’t hurt yourself so quickly, and because if it breaks anyway, it will break into small pieces that are less likely to hurt you. Many people are familiar with these images of car windows destroyed in car accidents. It can also be called safe because it provides increased protection against burglary for windows and doors.
Panels made of toughened safety glass cannot be cut, drilled or ground after thermal treatment!
Laminated safety glass VSG
Laminated safety glass is the term used to describe two panels of glass that have been “bonded” together with a film to form one pane. In fact, these two panels are glued together with the film.
The designation VSG says nothing about whether the two panes that form the VSG are themselves made of safety glass (ESG) or of normal window glass. VSG panes consisting of two panes of normal window glass or float glass have the advantage over normal window glass that the shards do not fall down when destroyed, but stick to the film. Destroying or damaging these panels is similarly easy as with window glass. We therefore consider laminated safety glass made of float glass to be less suitable for railing infill panels.
However, laminated safety glass is also referred to as VSG panels that are made of two panes of ESG, ESG-H or TVG. These VSG panels additionally offer the advantages of ESG and TVG. We usually use these panels for railing infill and fall protection glazing.
We describe the most common and economical options for the infill of railings with toughened safety glass and toughened safety glass as follows:
1. ESG in glass holders
The simplest and most cost-effective way to install glass as balustrade elements in railings is to use toughened safety glass “ESG” in glass holders with building authority approval. There is a wide range of glass holders on the market. Many offers advertise with “Tüv tested”, “constructionally tested” or similar additives.
These additions are misleading! Glass holders that may be used in the area of railing infill and thus as fall-securing glazing must have a general building authority approval (ABZ).
Alternatively, the manufacturer of the overall construction must obtain approval on a case-by-case basis from the highest building authority of the relevant federal state. This is uneconomical and is therefore (almost) always ruled out.
Advantages of ESG in glass holders with ABZ
The installation of glass panels with glass holders between railing posts offers a visually attractive railing design that is popular with customers.
The use of toughened safety glass in glass holders makes it possible to install inexpensive panes that are ground on all sides in inexpensive holders made of die-cast zinc, for example. The edges are cleanly ground and can be kept clean without any problems. ESG is statically more resilient than VSG. For example, there are installation situations where, due to the height and wind loads, only toughened safety glass can be used when using glass holders with ABZ, but not laminated safety glass.
Disadvantages of toughened safety glass in glass holders with ABZ
Only clear glass or tinted glass can be used. The use of satinized glass as the most cost-effective way to achieve a frosted glass look is ruled out because the ABZ does not cover the use of satinized glass. The reason is that satinized glass is made by etching the surface of one side of the pane, roughening it. Statically, this meant a weakening of the glass.
Another disadvantage of tempered glass is that in the event of glass breakage, the pane is abruptly destroyed and there is immediately a hole in the railing at the site! In addition, the small pieces of glass fall down. Therefore, according to the ABZ, installation above traffic areas is not permitted. Another disadvantage of toughened safety glass in railing infill panels is the sensitivity of clear glass to dirt. It behaves no differently than windows. And anyone can see what is on the balcony from the outside.
2. Laminated safety glass in glass holders with ABZ
In addition to the cost-effective and in some respects more advantageous design of railing infill with toughened safety glass, it is also possible to use laminated safety glass (LSG) with white film to achieve a “frosted glass look”.
Advantages of VSG in glass holders with ABZ
The advantages of toughened safety glass already mentioned above are significantly improved by the production of laminated safety glass from 2 panes of toughened safety glass, especially in terms of safety, but deteriorated in terms of economy and suitability for everyday use.
In terms of safety, it is positive that when a pane of laminated safety glass breaks, there is not suddenly a hole in the railing, but the hole is still closed by the film to which the glass fragments adhere, but this filling is no longer statically loadable. As a rule, it is also the case that only one of the two panes is destroyed or damaged. This is clearly visible and the whole pane can be replaced before the VSG pane is completely destroyed.
In terms of safety, it is especially positive that no pieces of glass fall down, because they stick to the film.
Disadvantages of VSG in glass holders with ABZ
A laminated safety glass pane made of “VSG of ESG” must be significantly thicker overall in order to guarantee the same static requirements as a single pane made only of ESG. This is because the two individual panes of the laminated safety glass pane are each weaker than a comparably thick single pane of toughened safety glass. The ABZ, the manufacturer of glass holders, gives precise specifications for the railing height, railing post spacing and other parameters, as to which glass thicknesses and sizes can and must be used with which holders. We have little scope for design here.
Due to the overall thicker VSG pane, more material is required, the film, which is not necessary with ESG, is added and the processing is more complex. This makes VSG panes significantly more expensive.
B. Manufacturing tolerances
The manufacturers of laminated safety glass made of ESG or TVG stipulate that the two panes bonded together may have an edge offset of +/-3mm without this being a reason for complaint. In practice, these offsets are more likely to be 1 to 1.5 mm, but they do exist and we have no influence on them and therefore pass these tolerances on to our customers. Customers who order laminated safety glass in glass holders agree to this!
C. Appearance and suitability for everyday use
In the front view of a balcony system, it is usually not possible to tell from a distance of 10 meters whether laminated safety glass with white film (frosted glass look) or satinized, non-permitted ESG with glass holders has been used.
Standing on the balcony, however, one can immediately see whether it is ESG or VSG. The upper side of a four-sided railing infill when using glass holders is always visible. And then also every layman sees that it is two panes and that the foil sits between them. But this need not be a problem and is a matter of taste. It is important to know, however, that this edge offset, which is visible from above, can also become a dirty edge and lends itself to this.
D. Water penetration between the panes.
There are rare cases of damage to VSG panes where water has penetrated the edge between the film and the pane and this has become visible as discoloration on the edge of the pane. We have no influence on this, and if the manufacturer of the panes cannot be proven to be at fault, we also refuse to replace such panes, as we have no influence on this.
This penetration of water cannot occur with panes made of toughened safety glass, since there is no foil.