The next issues (83 and 84) of FACES will focus on lightness vs. heaviness, two notions that often have an antonymic and antinomic relationship, signalling the opposition of two conceptual and practical propositions between which architects must in principle choose, based on their location, culture, and building tradition and in accordance with their aesthetic, technical, economic, political, and ethical convictions. This opposition brings with it many others, including ephemerality vs. durability, mobility vs. immobility, freedom vs. constraint, and fragility vs. solidity.

Presently, due to the combined effects of the demographic explosion, the depletion of natural resources, and climate change, this oppositional relationship, which has predominated in architectural thinking since the industrial revolution, is becoming more complex. A multitude of questions have arisen as to the role and mission of architects: to build or not to build, to demolish or to transform, to use highly processed building materials or more natural materials and shorter supply chains? The modernist ideology, which often developed in opposition to pejorative notions of heaviness and slowness, is now being challenged by the reintegration of concepts such as inertia, wear and tear, the patina of time, traces, or ruins. Taking durability into account, i.e. the long view, also compels us to appreciate differently what appears to be a new form of duality between the different efficiencies of light vs. heavy, because in contemporary architectural hybridisation, heavy and light are not necessarily mutually exclusive, and may even complement each other.

Favouring heaviness may denote a form of ecological insouciance that is collectively unbearable. On the other hand, preferring lightness may considerably increase energy consumption. In both cases, the choice made immediately engages the responsibility of the architects because it has a determining impact in terms of social inequalities, on a local and global scale.

In these circumstances, the question and evaluation of weight in architecture becomes paramount. In the 1930s, Buckminster Fuller praised the material lightness of his Dymaxion House, which was already a way of thinking about the ephemeral footprint of housing on American territory. Today, a new, less intuitive notion is changing the game, that of carbon footprint, which radically transforms our perception of mass: the production of 1 kg of polystyrene generates 6.68 kg of CO2 eq. when 1 kg of adobe yields 0.02 kg of CO2 eq1 A paradigm shift has suddenly occurred. The main unit of measurement has changed but has yet to be mastered, and the countless possibilities this shift points to remain to be explored. Although environmental performance tools are now a requirement for building, they are by no means sufficient for creating architecture and a mode of living together. The question is therefore not so much whether to favour lightness or heaviness, but, given the new operating conditions, to rethink and reinvent the relationship that separates and unites the concepts.

This reflection must also be an opportunity to evaluate the state of the art in terms of knowledge and know-how. Many examples from the past show that lightness and heaviness coexist as inseparable components: without heaviness, there is no lightness. The notion of equilibrium is used to balance economy of means and stability; no lightness without ballast, carbon footprint, and comfort; no inertia without mass. The return in force of prefabrication, which aims at an economy of means, as well as an efficiency of implementation, also has undeniable capacities of adaptation and transformation. A renewed interest in thick and massive facades accompanies a positive reappraisal of geo-sourced and bio-sourced materials hinging on the local availability of resources and leads us to take a new look at vernacular and Eastern architectures. Geometric abstraction is confronted with the wear and tear of time, while raw materials seem to absorb it, as the architectural skin and its ornamentation display the visual and textural nuances that mark its history.

Design brief specifications (programme, budget, deadlines, standards) no longer suit the needs of the time. With the urgency, scale, and complexity of the task ahead, a formidable field of research and experimentation is opening up for architects. How can they contribute to renewing the relationship between heaviness and lightness? What new types of implementation and layouts can they offer? What practices are these new building constraints likely to generate? How can the most efficient solutions be shared? What aesthetics will emerge from the different stances?

Candidates wishing to submit a proposal for an article should specify whether it relates to the issue of ‘light’ or ‘heavy’, or whether it touches upon both themes. The editorial board reserves the right to make a different assignment.

• 1. KBOB (Conférence de coordination des services de la construction et des immeubles des maîtres d'ouvrage publics de la Confédération Suisse), Données des écobilans dans la construction, 2016, https://www.kbob.admin.ch/kbob/fr/home/themen-leistungen/nachhaltiges-bauen/oekobilanzdaten_baubereich.html.