Chromogenic glasses: characteristics and types

10/01/2022 – The architect Richard Rogers, one of the leading exponents of the hi-tech architectural current, already stated in 1978 that “a building becomes a chameleon which adapts”, that is to say the building must become like a chameleon that adapts.

With this quote, the architect Rogers referred to the possibility of use alternative technologies and materials in order to achieve energy savings. Among these we find the vetri cromogenici, i.e. those glasses capable of modifying their properties, transparency and solar control, based on the stresses to which they are subjected and consequently regulating both the quantity and the quality of the light entering the building.

In a window frame or in one curtain wall the frame, or the metal frame, is the part that has the task of containing the thermal and acoustic flows. However, the glasses, which are only a component of a window or which constitute entire curtain walls, are an integral part of the building envelope and therefore play a fundamental role in what is the quality in terms of performance and energy.

In fact, there are already many on the market innovative and performing solutions such as low-emission glass, selective or reflective.

Chromogenic glasses are a further evolution of the technologies listed so far and their operating principle pursues i principles of daylighting design, the design discipline that promotes greater use of natural light inside buildings.

Chromogenic glasses are also called smart window, because based on the reaction that is triggered they have the ability to darken and become transparent again. A smart glazing controls the quantity of solar radiation or light that enters the building according to a rational management scheme of energy and environmental comfort. In addition, the feature of changing and adapting to the external environment allows you to create architectures not only performing but also interacting with the context in which they are inserted.

Chromogenic glasses are also used in other fields other than construction, such as the optics sector, the agricultural sector in particular for greenhouses and the automotive sector.

Chromogenic glasses can be divided into two broad categories:
1) not electrically activated, which have the advantage of self-regulation;
2) electrically activated, which have the advantage of being able to be controlled on command.

Chromogenic glasses that are not electrically activated absorb solar radiation, partially or totally, and based on the type of reaction they are defined:
vetri fotocromici, when the transparency varies according to the light intensity, the glass changes from clear-transparent to colored;
– thermochromic glasseswhen the transparency varies according to the temperature, the glass changes from transparent to slightly colored;

Then there are the glasses electrochromic which belong to the category of electrically activated chromogenic glasses. In this case the transparency varies according to the variation of an electrical voltage. The glass changes from transparent, when the electrical state is active, to colored (blue, gray, purple) when the electrical state is deactivated.

For all these new types, research is still underway to try to limit the disadvantages and instead enhance the advantages. Certainly between three types the one that has found greater application in building is that of thermochromic glass, which are used to create stairwells, roofs, atriums and courtyard structures, skylights and facade panels.

Electrochromic glasses in the building sector are used to make dynamic control windows.

Here are some contemporary experiments on envelopes with chromogenic glasses:
Solar house, in Saint-Nicolas, Italy, a 2011 project by Studio Albori.


Crossway, in Staplehurst, UK, a 2008 project by Eight Associates.

Chromogenic glasses: characteristics and types ©Archilovers

There have been several realizations all over the world, by way of simplification two Italian references are reported:
28 Duke of Aosta complex made in Brescia in 2009 by Studio Fuksas, where magnetron glass was used for solar control Pilkington Suncool™ of PILKINGTON ITALIA.

Chromogenic glasses: characteristics and types ©Archilovers

– the Emergency Urgency Department (DEU) of the Ospedali Riuniti of Foggia, where solar control glass was used COOL-LITE® SKN 154 manufactured by Saint -Gobain Glass.

Chromogenic glasses: characteristics and types ©Saint – Gobain Glass

Several researches have also been carried out on these products, such as the one carried out by ENEA during the period 2017-2018, entitled “Analysis of dynamic transparent components: energy performance, comfort and control strategies“, Which had the purpose of evaluating the influence of the control strategies of active dynamic transparent technologies (ie electrochromic glass) on the energy performance of buildings and on thermal and visual comfort, also investigating the implications in terms of energy flexibility and demand profile of the building with respect to the national electricity grid.

In short, i advantages of integrating dynamic glazed components actively controlled envelopes are:
– reduction of energy requirements;
– improvement of internal visual comfort;
– reduction of the peak loads of the plant and consequently of the electricity grid.

However, in the final report of the research it is repeatedly emphasized that to ensure the correct integration in construction of transparent dynamic technologies, a correct design of the control strategies is necessary.

Source: Le ultime news dal mondo dell'edilizia by

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