Sustainable Rehabilitation



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Last year, we set a very unusual exercise for my architecture students in Sicily: combining the subjects of urban design and restauro (restoration, rehabilitation), it attempted to explore the choice of the best perspective from which to intervene in the rehabilitation of buildings within the urban area, the most comprehensive scale for the relevant current concerns to manifest themselves in their full magnitude, and the challenges to be confronted and for which an answer must—also—be found in architecture.

The undergraduate program in architecture at the Kore University of Enna in Sicily, which these students are currently taking, organizes its learning around the paradigm that the city must be interpreted as the result of the social metabolism. That is, of the relations of society with its environment, and the mechanisms through which society obtains the resources it needs to perpetuate itself and reproduce. Such a metabolism may be regarded as a fundamental part of any culture, by no means unrelated to the organization of society itself.

In this way, the different urban models can be interpreted as reflections of different living proposals supported by different social metabolisms. The traditional city thus becomes a product of cultures whose resources are based on management of the territory, from which its social resources are obtained. The periphery of that traditional city, itself a product of industrial culture, has been forged on the basis of urban models proposed by the city planners of the modern architecture. These proposals for new cities tried to respond to the problems of the new industrial society with the resources that this new culture placed in our hands. The urban sprawl became the final expression of an advanced industrial society, with infrastructures to ensure mobility and communications on a scale unthinkable some decades ago.

However, in addition to the idea of the city as the expression of its social metabolism, the problem put forward by the program is how to transform our current industrial metabolism, which has turned out to be unsustainable, into a new non-polluting metabolism based on renewable resources, a sustainable metabolism that would preserve the quality of the environment. The problem is also how to use urban habitation and intervention to assist in that transformation of the social metabolism. The courses for the program thus dwell on an analysis of the ways of life proposed in each urban model. This reveals the social metabolism that supports them and contrasts it with the demand for sustainability, and also leads to proposals to transform it, re-inhabiting and rehabilitating our cities, and helping with the task of achieving a sustainable social metabolism.


This year, we are working on the traditional city. This is a city based on a necessarily sustainable social metabolism, since traditional society depends on the maintenance of the productive capacity of the territory, and on the availability of resources within a closed cycle where waste must be returned to the environment in the most suitable way for it to maintain its productivity. Such a metabolism requires an intricate management of the territory, configuring landscapes whose different elements—forest, fields, meadows, kitchen gardens, farm buildings, etc.—are interlaced in complex strategies for obtaining resources while maintaining fertility.

We invited our students to select a series of materials from historic buildings and to try to recognize the landscape from which they came. They had to try to reconstruct the landscapes that produced those materials and generated the architecture, and to say where they were and how much influence they had had. The exercise was then to be completed with the selection of another series of materials, this time modern and industrial, in order to ascertain which landscape produces these new materials, and what kind of influence it has.

As a trial exercise, we worked in the first workshop of the course on the façades of the historic center of Catania, the second largest city in Sicily, selecting the most frequent materials, the ones which left the greatest mark upon the urban environment. We discovered that these materials were directly linked to two of the most memorable episodes in the history of Catania. The first was the eruption of the volcano Etna in 1669, when the city was approached by a massive tongue of lava that was diverted away from the town and towards the sea thanks only to the city walls. The second was the complete destruction of the city a few years later, in 1693, by an earthquake, and the subsequent reconstruction of the settecento historic center we see today.

The students discovered that lava stone, the cold and solidified residue of the volcanic lava that had menaced the city, formed an essential part of the material with which Catania was rebuilt. Together with what remained of the city that stood before the earthquake, the hard stones from the lava that reached the city in the eruption of 1669 were used for paving and for the buildings’ walls. The softer and more porous stones from the eruption were used to make sand for facing walls, giving the intonaco (plaster) of the urban façades of the historic center their characteristically grey color. Furthermore, the clay from the countryside around the city, baked by the burning tongue of lava during the eruption, originated a building material of characteristics similar to the Roman puzzolana, which was obtained by excavating the clay from underneath the crust of solidified lava. The pink facing on many walls was produced with that material, and even today the black of lava and the grays and pinks of the façades are the specific colors of Catania, used also in modern constructions as a sign of identity although now obtained from other materials.

My students must next work on their own city of Enna, in the center of Sicily, and select the materials that were used to construct some of its historic buildings and make them inhabitable. They will discover that the city, located on a mountain like so many others in Sicily, grew by excavating the materials for its walls from the rock itself. They will wonder about the forests that produced the wood to build the ceilings. Where are the forests of Sicily today? And what was their relationship with crop farming, and with the famous Sicilian wheat that used to supply Rome? And with the wood used for baking lime?And for heating? They will also wonder about the water, including both the water drunk by the inhabitants and the rain water that fell on the roofs. And on the streets of the city, which formed stream beds organized to manage and take advantage of the water they drained away.

By looking at such things, they will have already noticed that the streets of Enna, their own city, are paved with lava stone from Catania. How and when did it get here, eighty kilometers away from the volcano? It arrived with the railway, when the industrial revolution made communications easier and allowed heavier and cheaper materials to be transported over longer distances, enlarging the landscapes from which cities were constructed and broadening the mark of their social metabolism, up to the point where it has now become global. This, however, was made possible by burning coal to fuel the railway, thus reducing transportation costs by externalizing other costs, which we are now starting to pay in the form of climate change.

When my students analyze the landscapes that built the historic city, they will discover some that were close at hand, and will see how closely intertwined the different elements of those landscapes were with the different resources society obtained from them. They will understand how closely imbricated the production of architecture was with the fulfillmen needs, and to what point the urban metabolism was connected with its own territory.


And also how distant are the landscapes which contain today’s construction materials, like cement and steel. How far off in space and time—eons since their formation—are the fossil energy resources used to produce them, just as the effects they will have on the climate will reach the farthest limits of time and space. And it is the same energy as is used to make the buildings comfortable, or to bring water to people’s dwellings, or to activate the infrastructures that support our urban metabolism. How remote and tremendous are the landscapes formed by the bauxite mining that supplies the aluminum for our windows. It is no longer under our own feet, nor does it organize our lives or activities, but it does affect other lives of which no news reaches us. We must recover the space and time of our way of life. That is sustainability.

Half the world’s population now lives in cities. From now until 2050, the population is expected to grow by the equivalent of the current populations of China and India. This growth will occur in cities, and mainly in cities that already exist and are going to expand and become transformed. These cities are the reflection and the result of the ways of life that have created and used them, of society’s relationship with the environment, and of their social metabolism.

The challenge will make it obligatory to transform cities, re-habilitate them (that is, restore their habilitas, or ability) to take in people who have mostly emigrated from the countryside to the city, or have formed part of the great migratory processes that are shaking the world and are largely due to the transformations brought about by our unsustainable industrial system of production, now globalized. These cities, then, must be cultural crucibles, confronting their challenges with the social and human capital of these people from different cultures who have been forged by very diverse landscapes, and who forge them in their turn.

At the same time, such cities must undergo the challenge of transforming their social metabolism. As the space of our global culture, cities are going to be the setting, indeed the battlefield, where the change in production models toward sustainability will take place. This is so because they are high-density nodes of our social metabolism, and because they are the places where the conscience of the citizenry has the best perception of what is happening in the public space within them.

The challenge of sustainability has strong urban expression in all the areas that define the city. Obviously, this includes building. For example, if we do not bring about a much more profound change than we are now doing in the way we construct buildings and keep them inhabitable, the provision of housing for the increased population in 2050 will demand of the construction sector all the greenhouse gas emissions that will be admissible that year if we are to keep the rise in the planet’s global temperature below two degrees Celsius. This is a giant challenge, and all the more so if we consider that it is one that also faces mobility, food, education, and many other goods and services necessary for living with dignity.

The increase in urban population over the next 35 years from today’s 3.6 billion to 6 billion will not only engender an urban crisis, but must also be accompanied by the necessary change toward the sustainability of the production model.

It is for this reason that the understanding of a city as a product of the social metabolism, as the expression of a productive landscape where society’s relationship to the environment is visible, has so much value today. Remaking cities to cope with exceptional growth, and doing so while transforming our model of production toward sustainability, requires networks that relate city and productive model, and resources with which to weave and unweave those networks. These are cultural resources which largely arrive with the new urban population. They come with them, entwined in tangles of knowledge which have to be wound into new frames with a new way of re-habilitating and reinhabiting cities.

Perhaps the image of Catania threatened by the lava of Etna in 1669 is a good analogy for the situation of cities today. Confronted with a huge challenge—that of emigration toward the cities, which seems about to destroy them—they may find that it actually permits the reconstruction that is so badly needed to face a still greater challenge.

For their last paper of the year, my students have to propose rehabilitation projects for the buildings they have been working on. They have to propose uses, and obviously, they must suggest strategies so that those uses will be suitably and sustainably implemented, with renewable resources and integration in a non-polluting social metabolism. They must be aware, however, that they are contributing with those resources to the construction of a new landscape, one in which their building resource strategies must link up with other resource strategies (food, mobility, etc.), and that their task, and the work they will have to carry out in the future as architects, is none other than the construction of a new landscape, the product of a new social metabolism.

Believe me, I am anxiously awaiting the results of their work.




Arquitecto por la Escuela Técnica Superior de Arquitectura de Barcelona, es profesor titular e investigador en el Departamento de Construcciones Arquitectónicas de la Escuela Técnica Superior de Arquitectura del Vallès de la Universidad Politécnica de Cataluña (UPC). Sus investigaciones se centran en las relaciones entre arquitectura y sostenibilidad, tanto desde el punto de vista del desarrollo de una nueva visión en el campo de trabajo del arquitecto como desde la creación de herramientas que permitan aplicar dicha visión. Entiende la sostenibilidad como la exigencia de cerrar los ciclos materiales en los procesos técnicos que satisfacen las necesidades humanas, y en este sentido el objetivo del trabajo de Cuchí es el estudio de los procesos que determinan la habitabilidad —la utilidad social básica que aporta la arquitectura— y su aplicación a los diversos ámbitos de decisión del arquitecto. Algunos de sus trabajos más importantes son Parámetros de sostenibilidad (2003), Arquitectura i sostenibilitat (2005), Las claves de la sostenibilidad (2007) y el informe Sobre una estrategia del sector de la edificación frente al cambio climático.

Download Paths to sustainability S.M.A.R.T. (PDF)

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