by Thomas Foschini20   Maggio   2019

Ventilated curtain walls: the evolution of anchorage systems

The proposals of producers of technology. The watchwords: pre-assembly in the factory and installation simplification.

The anchoring technology and installation of ventilated curtain walls in ceramic material has evolved significantly since the pioneering solutions of the early Nineties following, on the one hand, contemporary architectural trends and, on the other hand, tackling from all angles the problems linked to installation in the building site, focusing on the questions of safety, durability and – obviously – costs. We’ve been discussing the situation with leading operators in the sector who work on a daily basis with the major companies in the district for the development of innovative design solutions.
“The classic products with visible clips or Keil plugs – explains Luigi Garattoni, sales manager of Aliva, Ivas Group, based in San Mauro Pascoli – are no longer a new concept on the market. For this reason, we have invested in the research and development of new solutions such as Ariacovering, a system produced with patented technologies and processes, composed of a honeycomb panel in aluminium which allows for the anchoring of ceramic slabs of any format, also up to 1.5x4.5 metres”.
The gradual increase in the size of slabs, together with a reduction in their thicknesses have, in fact, posed a significant technological challenge for producers of mechanical anchorages, starting from the greater difficulty of riveting an ever finer slab. “With the Ariacovering system with an aluminium honeycomb panel, a ceramic slab starting from a thickness of 3mm and up to 7-10 mm and beyond can be assembled, also given that the high rigidity of the panel does not require significant thicknesses”.
The Aliva solution – which, Garattoni explains, would present the best costs-benefits ratio for fine 3-6 mm slabs – also stands out for the particular attention to the question of safety. The Grenfell Tower fire in London, with the consequent clampdown regarding fire-safety regulations which, at least in North Europe, apply to this matter, was a heavy blow for suppliers of components for ventilated curtain walls.
“Our system – Garattoni underlines – is fire class A2 guaranteed (the first applicable class after fireproof products, that is, “non-combustible” products, Editor’s note). All the certifications have been issued through Certimac in Faenza, with over 20 specific tests that guarantee the durability of the product”. Even before the question of fires (which, in effect, relates more to the insulation rather than to the ventilated curtain wall itself), the theme of durability over time has increasingly become the most pressing issue in recent years. The use of glues and chemical agents, increasingly used to reduce the costs of anchorage and installation in the building site but whose resistance is, by definition, limited over time, have been accused as the cause of rapid “delamination” (detachment of the slab). “For this reason – Garattoni concludes – we have made a double choice. The first is to use exclusively mechanical anchorage systems. The second is assembly in the factory, in a controlled and repeatable environment.”
Prepared and cut to measure, the panel is placed on the structure pre-assembled in the building site. The same ceramic slab is handed over to the installer complete with pre-set holes in the back and accompanied with an “assembly kit”. It’s a sort of Ikea model, in effect, to eliminate any possibility of error and to reduce problems and waste during the installation phase (the latter being potentially of significant impact, given the unit value of the slab product). The future in Aliva is called “Face”, a project – moreover entitled to European funding as part of the Por-Fesr 2014-2020 Programme – which aims to transform the slab-panel assembly phase into a veritable application of an “accessory”, which leaves the factory ready to be assembled on the metal framework, thereby further reducing times and costs.
 

Internalising the various phases – including the finishing – selling not only an anchorage system but a real turnkey project for architects and designers, is the challenge facing the producers of anchorage and installation technology for ceramic ventilated wall curtains. This is the view of Elio Navone, the longstanding sales director of Geos Italy, the company based in San Mauro Torinese which has been working for 13 years on the patent of the same name, registered in 2006. “The technology has evolved, and has been refined over time. Today we have systems dedicated to the anchorage of fine slabs, with thicknesses starting from 5.5 mm.”
Geos, while opting not to do without the use of chemical glues, has also developed a system substantially based on mechanical attachment. “An undercut slot is inserted in a special milled ovoid inside the ceramic slab by means of a 90° rotation of the shaped stud bolt”. From this point of view, the structural adhesive acts to “compensate dilation between tiles and aluminium” on the already fixed slab, rather than that of supporting the product, already perfectly anchored mechanically. 
Again with the Geos system, all the slab preparation phases are carried out in the controlled environment of the factory, “to then be able to go to the building site with a procedure often defined as ad hoc, the processes and designs being, for the most part, customized.” As a matter of fact, the extreme variety of solutions both in terms of design and aesthetics confirms the view of Geos’s sales manager: “'The' ventilated curtain wall does not exist, but rather a series of designs, to be managed on the basis of targeted construction and installation solutions.”
“We were among the first to develop a ceramic ventilated curtain wall with zero grout lines, which means intervals between the slabs of less than 5-7 tenths of a millimetre”, Navone explains, referring to the latest architectural trends that particularly favour this type of installation. With regards to installation in the building site, Geos puts particular attention on the simplification of the operations, not only to avoid errors, but also to limit the costs of this phase, which have a significant impact on the total costs of the project.
And safety? “What happened in Great Britain – Navone confirms – heavily depends on the type of insulation behind the ventilated curtain wall. Of course, the problem of the high temperatures of the interspace would end up causing the slab to burst, and to get round the problem we have inserted divisions in a number of new solutions to prevent excess ventilation. It’s unlikely, however, that a fire would be able to pass through the wall, which is closed by aluminium at the back, a solution that, regardless of the dimension of the grout line between the ceramic slabs, avoids the deposit of water and dirt in the interspace”.
What to do if a slab breaks? A first solution is to install anti-fall nets, but – as Navone warns – these also fail to offer a permanent guarantee. “Generally, when a slab breaks we are faced with a structural problem of stability for the entire building”. The standard solution to avoid every type of danger – including for walls installed near pedestrian areas – is to accompany the mechanical fixing with bonding to aluminium gangways, a sufficient and – according to the Geos sales manager – higher guarantee compared to that obtainable with ceramic slabs fixed with Keil plugs.
One of the most important projects currently being developed by Geos Italia is the ceramic ventilated curtain wall on a building in Milan, behind the famous “Pirellone” building: 100 m high, 15 mm slabs, grout lines of 1.8 mm. “The site management requested a certificate of resistance of the slab at a pressure of 450 joules which is higher, in fact, than that of a parapet”.
In general terms, GEOS technology reflects the principle of the solution patented 13 years ago. What’s new? In line with the trends in the sector, the new developments are the pre-assembly in the factory and the guided fitting. But that’s not all. “The most important challenge of recent projects – Navone explains – lies in identifying how to fix the substructure to the building walls, given that often we have had to deal with insulated walls, external coatings, structures in lightweight concrete (but also completely in wood or OSB) which have an infinitely lower resistance compared to a walling made with standard materials, and which are not suitable for traditional Fischer or Hilti-type plugging. We have searched for an internal solution in these cases, and we are working on various important projects, from Switzerland to Italy.”
Certifications play an important role, also in Geos: “Every single load leaving our factory is accompanied by an Accredia certificate which records the samples on which the resistance and seal tests of the ceramic slabs have been carried out. As a matter of fact – concludes Geos Italy’s sales manager – it would be extremely convenient for us if there was a CE mark for the installation of the facades, while the current regulations defer everything to a calculation report.” In other words, a European mark for the entire wall-system would make it possible to shift responsibility for the work from the installer (which, in Geos’ case is, in any case, an employee of the company) to the producer of the slab anchorage-fixing system.
With regards to evolutions related to the consumer, Geos has also had to face the competition of totally “by direct bonding on the profile” systems. “Any adhesive, unless applied directly on the plaster can create problems over time. We focus on a niche market which values safety and durability over everything else”.

A rather clear distinction between technologies and systems for the installation of standard ceramic slabs (10-14 mm) and fine slabs (from 3.5 to 6 mm) is offered by the systems of Progest, the company based in Verona that designs and makes ceramic ventilated curtain walls with particular attention on the possibilities that this technology offers not only on new constructions, but also for the energy upgrading of an existing one.
“For standard ceramic coverings – Progest’s sales manager, Walter Micheloni, observes, - various fixing solutions are available, exposed with ‘clamps’ in thermos-varnished steel, harmonized with the colours of the tiles, or hidden, with steel inserts placed in holes at the back of the slabs, used to fix the aluminium hooking brackets. A new hidden fixing system is also available, with a notch of 1.5 mm on the horizontal edges of the tiles in which the support and holding brackets will be housed.”
For large-size slabs and with a thickness of less than 6 mm, a bonding solution is preferred “with the system validated and certified by Istituto Giordano for load testing under pressure and depression”. In this case, Micheloni points out, “the anchoring of the ceramic slabs to the supporting structure occurs by means of certified structural bonding, with the use of “L”-shaped profiles positioned on the back of the slabs. These profiles have special slots for hooking to the adjustable supports, suitably set on the vertical uprights”. All the operations in this case are carried out in the building site, on the part of specialised workers.

Safety – albeit in the absence of specific regulations – is at the centre of Gavazzi’s proposal, the Lecco company that doesn’t work on the finished product (the anchorage system) but, rather, on sized fiberglass nets which, applied on the back of the ceramic slab with appropriate glues, prevent its fragmentation also in the event of breakage. “The reinforcement nets – Gavazzi’s sales director, Dario Buzzi, explains – are applied for two reasons: the first is to increase the resistance, and therefore the durability, of the wall; the second is for withholding fragments in the event of breakage”, a function the importance of which is directly proportionate to the height of the wall and its location near heavily trafficked pedestrian areas.
When dealing with buildings which are tens of meters high, in fact, the detachment of even a small fragment is sufficient to cause significant harm to people: “We offer in our product range two distinct types of reinforcement nets, the first of which is by far the most sold, that is, a fiberglass net of 10 mm thickness and with a highly reduced weight, just 100 g per square metre”. A resistant and light material by definition, the fibreglass is naturally subject to a coating process (“a covering with a mix of additive resins”, Buzzi explains), which are able to lend the net important fireproof or “self-extinguishing” qualities. Again in this case, there is no single regulation, apart from particular attention towards this aspect in the United States, Japanese and German markets.
“To apply or not fireproof coating – or applying or not the reinforcement net itself – is usually a question of costs. To minimise them – Buzzi points out – some companies have set up robotised systems for applying the glue between the net and the slab”, assuming, however, there are significant economies of scale. Separate consideration, also in this case, needs to be given to the bonding glues: “The mechanical resistance guaranteed horizontally and vertically is well above 1000 N/5 cm, that is, equivalent to the weight of 3 times that of steel – Gavazzi’s sale manager underlines – clearly meaning developing a procedure that guarantees optimal adhesion and, exactly for this reason, all the operations to prepare the ceramic slab are carried out in the factory by the producer or by an appointed third party.”
By its nature, the Gavazzi proposal is applicable regardless of the format and the thickness of the slab, the reinforcement net being supplied in rolls that will be suitably cut and applied, tile by tile, (becoming a structural part of them). What is more, the current market does not just live by large-sized slabs. There are various architects who, precisely to be different from the mainstream, are going back to small format ceramic applications. As a result, the problem of the optimization of costs, the guarantee of installation without renouncing the benefits of mechanical fixing, could appear to be the major question today.

“We’ve been building ventilated curtain walls since 1988 – the owner of Dallera Tecnologie, Franco Dallera, explains – and based on experience, I can say that the bonding problem doesn’t exist as such, unless linked to the guarantee offered by glue producers and the conditions for the installation of the ceramic material in the building site. Modern adhesives are certified for resistance of the order of 12 kg per cm², offering more than sufficient guarantees from this point of view.”
The situation is different with regards to the question of safety. It’s necessary to consider the need for maintenance of a building over time, also simply for plant maintenance. “It’s clear – Dallera explains – that a glued ceramic slab cannot be removed. Using these systems, which are initially less costly, means that every maintenance operation, also a simple inspection, involves breaking the slab and its subsequent replacement.” Designers must be careful, therefore, in choosing one solution rather than another which implies initially higher costs but which have significant savings regarding any maintenance work.
Among the latest developments of the Dallera range for ceramic ventilated curtain walls there is Luna Slot, a system available in both hidden and exposed versions that offers the possibility of removing the slab at any time, also if installed with “zero grout line”. It’s not correct, therefore, explains the owner of the company based in Agrate Brianza, to identify this system as “top of the range”. “In actual fact, the top of the range is obtained through specialising and optimising the installation – Dallera explains – to the extent that any device that makes it possible to save time in this phase gives rise to an enormous cost benefit and an improved aesthetic result.”
In contrast with other producers, Dallera “does not work with screws and rivets. Our system consists in the coupling of stainless steel springs that snap in and act in contrast. The first patented system of this type is the Venere range, which has been on the market since 1988, with completed projects – the owner notes – that are still in excellent state of repair today.” The contrasting clip, Dallera affirms, “offer complete stability over time, besides the possibility of adjusting the grout line to a tenth of a millimetre”.
The Dallera installer – in the building site without a drill but armed only with a laser and hammer – acts on the pre-structure already pre-assembled in the workshop. With regards to large formats, “the projects with the best costs-benefits ratio have been carried out with ceramic slabs of around 1 cm thickness”, given that the finer slabs, up to 3-5 mm, imply significant problems from the point of view of the mechanical fixing (which, the company owner points out, explains the return into play of less expensive bonding systems).
 

Removing the whole question from architectural elitism, proposing sufficiently economic, but at the same time, durable solutions (a slab fixed and glued but which is, also, removable, is currently subject to research and development by Dallera) appears to be the main challenge for the world of ceramic ventilated curtain walls for the next few years. It’s a further step towards the definitive maturation of a sector which has opened up extraordinary opportunities for the promotion of Made in Italy ceramics both in Italy and abroad.