Stone, Earth, Wood, Straw, Stubble & Co.by Dominique Gauzin-Müller
Focus on Circular Building
Ecological, healthy, bio-based, natural: these are the adjectives used to define materials as old as time, rediscovered after they had sunk into oblivion (and contempt) for decades. Renewable, recyclable, often recovered from agricultural and forestry waste, in France they are thriving thanks to the creativity of projects able to combine tradition with more innovative technologies.
The innovative use of poor materials (wood, straw and other vegetable materials, earth and stone) is becoming more and more popular in residential buildings, both in public works and in large building complexes. In France, the government and local administrations started promoting the use of such materials deriving from short supply chains, able to promote the resources of each region.
By 2012, the annual chart of wood buildings and the national Prize for Architecture in Earthen Architecture (CRAterre) in 2013 were proof of the architects’ creativity and the worforce’s competence, thus confirming France’s pioneering role in the field.
Professionals in this sectors have shown an interest in the promotion of such natural resources by devoting the French pavillion to eco-local materials at the UIA (International Union of Architects) held in Durban in 2014.
Then, the exhibition “Matières en lumière” that has presented over 70 models made out of wood, earth, straw and stone, rased considerable interest amongst visitors and awe at the ability of such projects to adapt in urban as well as rural areas.
Reuse is another fondamental strategy: 50% of waste produced in industrialised countries come from the building sector: it is all the more urgent to stop such flow and start imagining a new life for it.
An indispensable perspective in such a period of ecological and social crisis, the circular economy aims at producing goods and services limiting the use of raw materials and energy. In the building sector, such approach pushes toward local and decentralized production: materials have to draw on abundant natural resources while energy must tap renewable resources (sun, wind, geothermal etc.). In France, the circular economy has officially been introduced in the national policies in October 2014, with the Code of the environment included in the law on energy transition and green growth. A true revolution for a country historically centred around its Capital! Starting from now, ministries and local communities are trying to devolve the circular economy according to local needs.
So, local actors (for example single municipalities, inter-municipal consortia, technical services, companies, associations, citizens) are gathering around a development strategy, creating new job opportunities, in particular in the more disadvantaged rural areas.
This approach, already tested in Voralberg, a small but thriving federal state in Austria owing its prosperity to a green economy was able to promote its resources, timber and other locally-produced materials.
This is also the spirit of the territorial economy theorized by Alberto Magnaghi strongly linked to the bio-regional culture that in France started a widespread network of experiences.
So, in Europe a series of strategies able to bring benefits on multiple levels are starting to emerge, thus showing how the ecological transition is far from an image of ascetic renunciation! It is a change of paradigm towards a society that once was more frugal and happier, giving back a meaning to everyday and professional lives.
Pierre Rabhi, the French philosopher of agro-ecology, defines it as “happy sobriety”. To do more with less, while finding the pleasure of freed creativity.
Wood, a General Interest Supply Chain
France is the third European country for the size of forest coverage. Therefore, wood is ranking first amongst eco-local building materials. Its use is a national tradition: from Alsace to Normandy in lattice homes and farms to churches in the Champagne region. In the South-West, oak carpentry for large-size premises still shelters some covered markets after six centuries.
Broadleaf and coniferous trees are a perfect match for eco-responsible architecture if coming from forests managed according to sustainable criteria near building site areas, if they are not treated with chemicals. Anyhow, wood is the only structural material which is renewable and its processing require a low energy input. People are increasingly using wood and they are more and more aware of its numerous advantages. Over the last five years, its use in the building sector went from 5 to 12% in single-family homes where it is particularly appreciated for the smoothness it confers to surfaces and for its warmth.
But besides these emotional characteristics there are also a number of technical and economic advantages. The gross surface being equal, a house built with wood and reinforced isolation in the vertical elements allows to have a larger useful surface by 5-10% compared to that of a brick house.
It also boasts better thermal performance able to reduce energy consumption for the heating. Moreover, no big machinery is needed to build a woodden structure, thus reducing noise and unwanted dust. Installation in a dry supply chain and prefabbrication in a workshop shorten the life of a building site, with clear advantages on costs and the logistic organization of the urban area. In addition, the lightness of the material helps self build, preserve the integrity of the natural environment in the most fragile sites and helps build on soils with little load bearing capacity and on steep slopes.
Besides wood, other building materials from bio-based resources are becoming increasingly popular and their use is encouraged by joint programmes between Ministry for the Ecology, Housing and Culture.
Hemp, flax and stubble are particularly interesting because their growing cycle is a lot shorter compared to a tree. As for straw, nothing more than agricultural waste, rather than burning it in the fields and thus producing CO2 emissions, it is a lot cheaper to use it as economical insulating material with low grey energy content. Currently, in France, there are over 2,000 buildings equipped with straw insulation: the small houses built in the 70s and the 2000s, public buildings such as the St. Louis School in Crest, the multifunctional room in Mazan, near Mont Ventoux, the school complex of Issy-les-Moulineaux, on the outskirst of Paris, where 6,000 straw bales were used. But also the Making Hof complex of terraced houses in Strasbourg acted as a training building site and, during a work of social building carried out in 2013 in Saint Dié-des-Vosges two buildings with a wooden structure and filled with straw were built, of which one 8-storey building for a total of 26 houses.
The innovation of geological materials (earth and stone) follows that of the bio-based ones, complementing them. With the limestone of Vers used by the Romans to build Pont du Gard in the first century BCE, architect Gilles Perraudin and his students build today, in the South of France, comfortable schools and social buildings – without air coditioning – even in the hotter months.
In France, raw earth has been used in the building sector for a long time, with technologies developped to adapt to specific characteristics of any kind of soil: pisé (rammed earth) in Alvernia and Rhône-Alpes, bauge (earth with straw and other fibres) in Britanny and Normandy, adobe blocks (a mix of clay, sand and straw) in the Toulouse area, torchis (wood structure filled with earth) in Landes, Alsace and in numerous medieval historical centres.
The almost eternal duration of buildings constructed in this way is proven in various climatic areas, once they are adequately protected as it happens for the woodden buildings “avec de bonnes bottes et un bon chapeau” (“with a good pair of boots and a good hat”). Moreover, an earth house guarantees a healthy indoor microclimate: humidity control, reduction of toxic substances in the air, ability to absord noises and smells, thermal inertia. Raw materials are generally availabe near building sites, thus making transport almost unnecessary. And this is a suitable material for self-build, a particularly important characteristic for emerging countries.
Besides, all over the world there are more and more projects revealing the aesthetic properties and the modernity of a raw earth building. The Terra Award, first world prize devoted to earthen contemporary architecture is proof of this with its 357 applications from 67 countries from the five continents. The 40 shortlisted projects are presented at the “Architecture en terre d’aujourd’hui” itinerant exhibition which in 2017 will stop in Italy as well (Milan, Turin etc.).
Because of population growth and the increasing scarcity of resources, it is fundamental to promote the use of eco-local materials. In France, a number of social investors are convinced about that. By adopting a participatory process involving the future users and neighbours, Aquitanis in Bordeaux and Actis in Grenoble are working on projects combining wood and raw earth. Because what is truly ecological is using the right quantity of a good material in the right place. A smart combination of building materials helps optimize the performance of each and every one of them, meeting every building, ecological and economic need. Stone, earth, bricks and concrete give wood the necessary thermal inertia to guarantee summer comfort, while acting as sound screen and fire barrier. Steel plates, screws and tie beams reduce the carpentry wood section, creating performing as well as elegant combinations. Aesthetic quality and imagination are fundamental factors to convince and motivate clients.
France boasts three of the world’s three leading operators in the field of construction and public works. This obviously has consequences: the lobbies of the cement, steel, aluminium, glass and PVC are very strong, which slows down the development of eco-local materials. Today, though, even production sectors linked to bio-based or geological materials are getting organized.
While behind reused materials, there are no lobbies and there is no supply chain as such. Their use refers back to some of the 8 Rs suggested by Serge Latouche, the degrowth economist: reduce (the use of raw materials), reuse (materials and buildings), recycle (buildings’ components), relocate (favouring short supplies). The pioneering companies in the sector have mainly focussed on eco-social recycling of paper and textile materials to make insulating materials. But a few militant architects not only experimented the structural performance of reused materials, but also their poetic force. The Art Museum in Ningbo, China – designed by architect Wang Shu – where whole walls have been built with reused stones and bricks is an excellent case in point. The variety of possible ways to reusing in architecture (matter and building products) has been skilfully showed in the itinerant exhibition “Matière grise” – opened in 2014 at Pavillon de l’Arsenal in Paris – which raised considerable awareness amongst architects.
Wood, earth, stone, straw or with a combination of materials, including some recycled ones, tomorrow’s buildings will have to be healthy and with minimum impact on the environment. Aware of their own responsibilities, citizens, users, architects and the construction companies must combine their effort to find together economically viable and accessible solutions, which can be original and creative at the same time.