Technical and architectural history of the minimalist window

Carlos Machado e Moura
Pedro Borges de Araújo 

New paradigms of development

The possibilities of glass as a load-bearing element, associated with structural bonding with new materials, brought about a true architectural revolution, allowing the construction of structures and pavilions entirely made of glass. This possibility of radical transparency seemed, finally, to achieve the desires of transparency and immateriality advocated by the Modern Movement. However, the critique of modernity brought about an important paradigm shift in the architectural perception of the window and the glass façade at both the formal and functional levels.

4.1 Between the formal versatility of glass and the reconsideration of the brise-soleil

As Juhani Pallasmaa points out in the text “Filters – Catching the Eye” [pp. 275-277] (88)88.  Regarding the way a vision-centred design and the consideration of the window exclusively as a source of light and of panorama have altered the very ontology of Modernity, see also: Juhani Pallasmaa, The Eyes of the Skin: Architecture and the Senses, Chichester, John Wiley & Sons, 2005, pp. 26-29., Postmodernity called into question positivism and the dogma of transparency, opening the way to the richer and more complex formal explorations of buildings. The evolution of this perception manifested itself progressively throughout the 20th century and and can be perceived in the sequence of essays compiled in The Light Construction Reader (2002) (89)89. The book brings together 28 essays that explore themes and issues emanating from the 1995 “Light Construction” exhibition at the Museum of Modern Art in New York. Todd Gannon (ed.), The Light Construction Reader, New York, Monacelli Press, 2002.: between Paul Scheerbart’s “Glass Architecture” manifesto (1914), the first questions raised in the influential “Transparency: Literal and Phenomenal” (1964/1971) by Colin Rowe and Robert Slutzky and the disenchanted visions of Antony Vidler and Gianni Vattimo (1992). Today, we could add to the list some other texts, such as Treacherous Transparencies (2016) by Jacques Herzog and Pierre DeMeuron.

These theoretical concerns found a practical response at the turn of the century, mainly through two processes. On the one hand, glass acquired a new formal versatility, being able to absorb a series of treatments that allow it to change its degree of transparency and colour, and to be the object of graphic printing, a process that the work of Herzog & DeMeuron introduced in an iconic and paradigmatic way. (1)90. Among the first examples, we consider the Ricola-Europe SA Product and Storage Building (Mulhouse, France, 1998), whose façade is composed of printed polycarbonate panels; the Institute for Hospital Pharmaceuticals (Basel, Switzerland, 1998) and the Information, Communications and Media Centre of IKMZ BTU Cottbus (Cottbus, Germany, 2001). On the other hand, buildings once again incorporated new exterior layers or “skins”, recovering a sense of materiality and textural variety lost with the extension of the glass to the entire façade. The works that Jofebar has carried out and which are partly illustrated in this book – including doorways, louvres and façades in different translucent materials – testify to the material and formal wealth of these elements in contemporary architecture, as well as the graphic possibilities offered by the evolution of digital printing processes. (1)91. Today, the development of digital printing allows us to use glass as an element capable of filtering, blocking and differentiating. This effect is enhanced by dual point technology, with overlapping impressions, which allow the glass two different perceptions, one on the outside and the other on the inside.

4.2 From the diaphragm window to responsive glazing

Parallel to these eminently formal achievements, there have also been important technological advances in the technical response of glass. Glazing has become an active and changeable element, capable of responding dynamically to changing environmental conditions, away from the inert and hermetic lamina hitherto advocated. Finally, Le Corbusier’s fenêtre diaphragmée, was achievable. He had argued as early as 1935 that “the glass wall can be, and should be, controlled with adjustable shutters inside the glass envelope”. (92)92. Le Corbusier, “Glass, the Fundamental Material of Modern Architecture”, West 86th: A Journal of Decorative Arts, Design History, and Material Culture, Vol. 19, No.2 (Fall-Winter 2012), p. 304.

But while in Jean Nouvel’s Institut du Monde Arabe (Paris, 1987) all the mechanics of the façade are exposed, the contemporary trend is precisely the opposite, making this entire process imperceptible and assimilated by the glass itself. Chambers between glasses have been explored for the introduction of filter elements – such as internalised meshes or in-built shading systems – and currently it is the glass itself that provides responsive glazing. The development of smart glass – switchable and dimmable glazing – began in the 1990s, but the first applications took place mainly over the last decade and are expected to reach a larger market share in the near future. (93)93. Among the various types, electrochromatic glazing – only suitable for tempered glass – consists of a very thin coating (less than 1 micron) formed by ceramic-based layers and electrically switchable metal oxides. With the application of low voltage current, the movement of ions (lithium or hydrogen) changes the transparency of the surface and consequently allows privacy control and limits the transmission of heat and sunlight. It is therefore also known as privacy glass. The response of the glass varies by controlling the intensity of the applied electrical signal, and can be programmed and connected to air conditioning and lighting systems through sensors. The glass thus becomes a device that allows the user to regulate the thermal gains and the luminosity, depending on the external environment and the needs of the interior. Alternatively, thermochromatic and photochromatic glasses are dynamic systems that do not require connections and electrical components. The properties of their coatings change due to exposure to heat (thermocromatic) or direct solar radiation (photochromatic), reducing the transparency of the glass. These technologies can be integrated with other solutions, such as low-E glasses, which do, however, have lesser versatility than electrochromatic glasses. Among Jofebar’s works with responsive glazing, Contour House (Peak District, United Kingdom, 2016) by Sanei Hopkins Architects uses glass from Sage Electrochromics, a subsidiary of Saint Gobain.


Mechanics of the façade exposed in Jean Nouvel’s Institut du Monde Arabe sunshades, Paris, France (1987). Photo: Serge Melki.


Installation of electrochromic glazing in Sanei Hopkins’ Contour House, Peak District, United Kingdom. Photo:  Pedro Gama / Jofebar.



4.3 Glass as energy generator and information transmitter

In addition to solutions that reduce the energy consumption of a building through the behaviour of glass coatings, the recent development of thin film photovoltaics allows the glass to be transformed into a solar energy generator through coatings composed of transparent cells, imperceptible to the human eye. Another possibility offered by metal coatings is the use of heated glass. Revisiting a technology initially developed for automotive glass, with the use of electric elements (already mentioned in chapter 2.9), this system was applied to conductive metal coatings invisible to the human eye from the end of the 1950s and applied to architecture to combat the formation of ice and condensation. While its applications to normal glass presented great heat losses, making it impossible to use as a source of heat for the interior of the building, with the advent of low-E coatings since the end of the 1980s – energy efficient and low emissive – the scenario changed. The glass can thus function as a space heater – Komfort Glass – a possibility that further enhances its capacity as a dynamic element of mediation between the interior and the exterior, able to regulate thermal comfort and even replace other forms of heating. (94)94. In spite of their feasibility, large panes of heated glass are, however, still relatively unused, because of their high price. Among the various uses of heated glass implemented by Jofebar in minimalist frames are, for example, Smådalarö Houses (Sweden, 2014) and the Turkish Airlines Hotel in Ortaköy (Istanbul, Turkey, 2015-17), the latter designed by David Chipperfield. For these projects, Jofebar and its partner Architectural Solutions developed a solution of electric power supply through dry contact, which makes the use of electrical components in sliding windows much less complex and particularly safe.

In addition to all these technological advances, glass has even become capable of conveying digitized information. While, in principle, the architectural applications of media communication technologies in contemporary society are more suitable to interior spaces, numerous functions can also be applied to windows. These, therefore, cease to be the optical screen of the Modern Movement to become a computer screen, tactile and interactive, capable of opening up a virtual world. These and other technological advances in glass are described in the text “Glass and Windows: the last frontier for smart and functional materials integration” [pp. 145-150] by Senentxu Lanceros-Méndez.

4.4 The frame: the paths of perfect seal and new materials

The main challenge with regard to frames has been to improve their response to ever higher technical requirements. Most curtain wall systems recommend the non-operability of glazing, separating its functions and relegating ventilation entirely to mechanical systems – revisiting some of the Corbusian mur neutralisant and respiration exacte principles. In this sense, as an element in the interaction between mechanical and passive energy management systems, the glazing sometimes sacrifices the feeling of connection to the outside, refocusing its role on the mere visual relationship and the source of natural light (possibly controlled). However, the glass door or window are elements that, in addition to the view, should offer the possibility of an effective connection with the outside, through air circulation, sound and spatial continuity. (95)95. With regard to airtight façades and the effect of the operability of windows on the feeling of comfort, see the interview: “Opening the un-openable window: Matthias Schuler” in Rem Koolhaas, AMO, Harvard Graduate School of Design, James Westcott (ed.), Elements, Marsilio, 2014, pp. 721-729.

In order to meet the increasing requirements of greater efficiency, research has focused on improving the performance of thermal and acoustic insulation, and air/water tightness, namely through the incorporation of more composite components. The life cycle of these solutions is much greater today, mostly due to a better mastery of manufacturing techniques, but also to the introduction of components that are more resistant to corrosion or even to the improvement of surface treatments. In particular, polyvinylidene fluoride (PVDF) paints, capable of maintaining their chromatic and protective properties for 20 years, have offered metal one of the advantages of uPVC frame systems: longevity without the need for regular maintenance. There is also notable progress in the field of engineered woods, which allow minimalist systems the possibility of using this raw material, with the same guarantees and benefits as metallic systems. We also highlight the efforts of some brands, such as AIR-LUX, in developing frame solutions with pneumatic sealing systems that offer a significant improvement in acoustic and air/water performance. Despite its complexity and price – which prevents its scalability of the solution – the solution points in the right direction, constituting an effort that is worthy of note. Like the lifting system hardware introduced in the 1960s, these innovations often correspond to intermediate – and necessary – steps in the development of more definitive solutions.

4.5 Between the suspension of gravity and invisibility

In addition to responding to ever more demanding technical requirements, the frame has the added challenge of ensuring a very easy and efficient operation despite the progressive and constant increase in the dimensions of the sashes and the weight of the glazing. In this sense, gravity-defying systems have been explored,eliminating the high wear shown on rolling systems subject to heavy loads and the consequently reducing their need for maintenance. Together with the wish for maximum transparency, the suspension of gravity is, moreover, the other great architectural axiom evoked by Eduardo Souto de Moura in ”Let us go back to the past; it will be a step forward” [pp. 156-166].

But if transparency – as we have seen – is now perceived more critically than it was in the past, the architectural desire for maximum formal purity that has always been associated with it remains in full swing. In fact, it is pervasive to all the achievements we have analysed and it is summarised, for better or worse, in the term ‘minimalist’. Although many of the changes made to frames and windows are mere exercises of redesign and formal mannerisms, there is a constant and guiding logic that consists in hiding the elements that today are intuitively perceived and will be obsolete tomorrow. On the contrary, the elements that have already reached their developmental climax are assumed and revealed. In this balance, glass has incorporated all mechanics imperceptibly and the accoutrements and engineering tend increasingly to be hidden in the profile. One of the most important and sophisticated elements of the building thus tends to become invisible.


Photo: Paulo Catrica