It may be a terrible message for our profession. Unknowingly to most people, facades have always defined our environment. And facades mainly have been defined by other factors than architecture. Architects however maintain the opposite. They believe they are creating the facades. The contrary however is all around us.

Some years ago a colleague asked after a lecture about cepezed architecture whether it would be possible to imagine a city made of steel and glass. It was answered by returning the question: "Could mediaeval man imagine a city of brick?" Time and other factors define the answer, not the material. To understand the future of the envelope it is essential to understand its past. Where it came from, where it stands. Facades are, in principle, very simple means of creating shelter. Identical to roofs, but the roof has miraculously resisted all specialists and retained its simplicity. And facades have gone wild and unintelligibly complicated. Why?

Basic shelter without added (complicating) requirements

Basic shelter started with cover against rain and wind. This gradually evolved in more advanced shelters which provided insulation to prevent loss of heat and, in hot climates, a cool environment. When mankind became more conscious about energy loss and more concerned about comfort, things started getting out of hand. When walls became thicker, and made in stone for fire protection, the thermal capacity of the building increased. This caused thermally slow reacting buildings which, once cooled down, require a lot of energy to heat up. To accomplish this re-heating capacity, costly installations are introduced. Another problem is that the effect on the inside temperature due to outside temperature oscillations is shifted: high mass requires a long reaction time which might be comfortable but in most cases leads to even more technical installations.

Figure 2: the effect of outside temperature oscillations on inside temperature

Next came high insulation values and maximized air tightness. This consequently gave ventilation and condensation problems. Mechanical ventilation devices were called in, which are costly and difficult to tune. These installations have become responsible for high energy use and loss (Figure 3) and thereby work contrarily.

Figure 3: The effect of several different properties of a building on the energy demand [1].

In general it can be said that solving façade problems introduced other, much larger, problems. Besides that, the solutions also had more and more effect on the building itself, and therefore shifted complications from the already complicated façade system to the rest of the building. It is clear that whenever any further requirement is added to the primordial façade, problems arise. Temperature, humidity, light, acoustics, fire, smoke exhaust, ventilation, energy use, have progressively muddled our thinking on facades, complicating them unknowingly more than needed. Consequently the façade has become one of the most costly parts of a building.

Façade technology covers the spectrum, from leaves, skins, textiles, timber, through stone, brick, and concrete to glass, steel, aluminium and plastics. Every step in material use comes with its own cost-benefit, and with its own social consequences. Parallel to this development, architecture has evolved as a result of the technical possibilities and needs. As for recent developments, we can discern the definition of integration of functions against the specialization of functions. In recent years the idea of integration of functional services and facade performances has been the mainstream thinking.

For example the load bearing sandwich panel is a development that cepezed introduced some years ago, originating in the trailer industry (Figure 4). Over the years the limits of integration have appeared in buildings, and they have led to even more complicated solutions.

Therefore solutions should be simpler, more basic and compact. The façade should be the climate regulating skin it once was, reacting dynamically without aesthetical consequences. Such solutions could be found in intelligent surface technology, membranes and even nanotechnology. Cepezed has been using membranes in buildings for over a decade. The purpose of these membranes, which include perforated steel as well as open woven PTFE coated glass fibre (Figures 5 and 6) ranges from windbreaker, fence, radiation screen to sunscreen and often a combination of such functions.

Today's urban planning and architectural design methods are very traditional. Yet demands on every level of planning have evolved greatly. Neither in the functioning of buildings, nor in that of cities' rigidity is of any durable value anymore. So the teleological thinking in the design methods and results is outdated. Any plan should be a step in a continuous process of development. This has been called ‘pliable planning' [3].

Since the façade defines the building's potential more than any other element, the façade should become pliable as well, which could be achieved in many ways. From a technical viewpoint, it can be achieved with moveable or interchangeable parts. The first is the usual opening window or hatch, the last a system of replaceable and interchangeable elements.

That was the way it was. The future will be materials that can perform the same way. Cepezed dares to invite the industry to pick up this challenge and join us for better building technology. The new elements we are introducing today are aerodynamics, filtering and flexibility. The goals are membranes, nanotechnology and molecular development to achieve this. Pliable insulation values, transparency, airtightness, pliable watertightness and vapour permeability must be developed for the future envelope. The technology exists to create new architecture, and a new and a even more durable built environment. The future should be more simple.

The Future Envelope

[1] Jokisalo ,J and Kurnitski, J Effect of the thermal inertia and other building and HVAC factors on energy performance and thermal comfort in Finnish apartment buildings, REPORT B7, Teknillinen korkeakoulu. Konetekniikan osasto. LVI-tekniikan laboratorio. B Helsinki University of Technology. Department of Mechanical Engineering. Laboratory of Heating, Ventilating and Air Conditioning. B Espoo 2005, Finnland

[2] Cohen, M.E., Lecture, Durabilité dans le bâtiment selon le concept de cepezed, Arene Ile-de-France, Concours l'Esquisse verte 4ème édition , 5ème Conférence Lundi 19 mars 2007, Paris

[3] Cohen, M.E., Article, Pooibaar plannen, Beter bouwen en bewonen edition 26 part 4, STT/Beweton, Den Haag 2004