double facades: history

The proposition of using the greenhouse principle to operate as a layering device for a building envelope was being extolled not long after Paxton had created the greatest glass building of all time, the Crystal Palace. In 1860 in The Gardeners Chronicle in the UK, Jacob Forst suggested that south facing glass walls creating sunspaces could be used to grow fruit, and would provide "an admirable arrangement for house ventilation". His idea was to circulate the air warmed by the greenhouse effect though the building behind.

This proposition by an English horticulturalist was a speculative fancy compared to the work carried out in America 20 years later, when Edward Morse, another botanist, developed what might be the first working multiple wall. Morse was aware of the effect already worked on by de Saussure, that the sun's rays passing through glass and falling upon a dark surface warmed the surface and the air in contact with it. He used his observation that dark curtains drawn behind a window became warm, and created warm air currents, and in 1882 built what was the first solar wall (what we now know as a Trombe-Michel wall, named after the "invention" of 80 years later).

In the book "Glasarchitektur" Scheerbart set out, in 111 sections, some of which are only two short sentences long, his vision of the future of architecture as powerfully dependent on the use of glass. It is significant that only one of these, no. 4, is concerned with how glass works in terms of what is now known as building physics. The book is generally a paeon of praise for the potential of the material to deliver a new aesthetic, and to resonate with the idealism which was endemic in the modern movement of the time. Walter Gropius and Adolph Meyer's Model Factory, which was also constructed at the Werkbund Exhibition, was another building dominated by glass as the symbol of the new architecture. Performance as we know it now played little part in this. Layering may get a mention in "Glasarchitektur", but the buildings of the contemporaneous modernists were single glazed, with glazed envelopes not much more sophisticated in environmental terms than Hardwick Hall

In Europe, the great modernist le Corbusier, saw an opportunity in his project for the Cite de Refuge, the Salvation Army Hostel in Paris. Le Corbusier had already used a second skin glazing system in his Villa Schwob in his home town of La Chaux de Fonds in Switzerland in 1916. Here very large windows (one of them two storeys high) were designed in two layers, with heating pipes between them, to prevent down draughts. Le Corbusier's propositions 15 years later were much more adventurous, and involved two complementary building systems: one to produce what he called "respiration exacte" (a carefully controlled mechanical ventilation system), and the other the "murs neutralisants", what he called "our invention, to stop the air at 18? undergoing any external influence. These walls are envisaged in glass, stone, or mixed forms, consisting of a double membrane with a space of a few centimetres between them ... a space that surrounds the building underneath, up the walls, over the roof terrace. Another thermal plant is installed for heating and cooling, two fans, one blowing one sucking; another closed circuit. In the narrow space between the membranes is blown scorching hot air, if in Moscow, iced air if in Dakar. Result, we control things so that the surface of the interior membrane holds 18?".

This proposition was much more than a rhetorical technological gesture. It was considered with some rigour in a test chamber set up by the French glass manufacturer, St Gobain, in 1931. The report on the tests carried out in the test chamber were interesting in the light of the proposition. The test engineers concluded that the system benefited from a third layer of glass trapping still air to make the system viable. This is not surprising: had section 4 of Scheerbart's "Glasarchtikectur" been noted, Le Corbusier and the St Gobain technicians would have read "To place heating and incandescent elements between the walls is in most cases not to be recommended, since by this means too much warmth or cold is lost to the atmosphere". Le Corbusier was more interested to in the imagery and symbolism of technology than he was in working out the building physics.

Such was the basis of Le Corbusier's proposal to install the "mur neutralisant" in the City de Refuge. The outcome provides one of the sad, or possibly humorous anecdotes of the modern movement. Le Corbusier was so keen to undertake the project that he offered a fee cut by 40%. Early projects had east and west facing walls, but, after battles with the Planning Authority the final project had its great glass wall facing just west of south. The budget constraints were severe, and the building finished up not only single glazed, but without the full air conditioning which Le Corbusier had proposed. Without either the "mur neutralisant" or cooling, the environment of the building was a disaster. The Prefet de Paris condemned the building, which had been the subject of complaints by the occupants, and Le Corbusier had to introduce opening windows into his hermetic facade. The environmental control of the building was eventually put right after a German bomb shattered the glass wall on 25 August 1944. The building was reclad in brise soleils between 1948 and 1952. By 1947 Le Corbusier was advising Senator Warren Austin in relation to the United Nations Building of his strong belief "that it is senseless to build in New York, where the climate is terrible in Summer, large glass areas which are not equipped with a brise soleil. I say this is dangerous, very seriously dangerous". In considering the history of the multiple wall this is doubly ironic. Harrison's UN building worked because of the air conditioning cooling delivered by the system Le Corbusier could not afford in the Cit de Refuge 20 years earlier. If the "mur neutralisant" had been tried for the UN Building, it would probably have worked.

Whilst Le Corbusier was working through the theory and (non) practice of the "mur neutralisant" in France in the 1930s, a more characteristically practical progress towards ideas of multiple facades was being made in the USA.

The first significant step was the bringing to the market in 1935 of "Thermopane', a double glazing unit manufactured by Libbey Owens Ford (LOF) comprising two sheets of glass hermetically sealed, with a 12mm air gap. This double glazing unit was incorporated into all the "solar homes" being designed by the Chicago Architect George Fred Keck. LOF's enlightened self interest led them to sponsor a year-long study of solar heating, with tests conducted by the Illinois institute of Technology. This work represents an early exploration not only of the use of passive solar design using multiple glazing, and the importance of a south facing orientation, but also of the effect of occupant use, building mass, and the importance of uncontrolled ventilation and infiltration. A second study funded by LOF between 1945 and 1947 showed the importance of optimisation of window area.

More significant in the development of the multiple wall principle was the Wallasey School built in 1961. St George's School Wallasey, designed by A E Morgan, incorporated a genuine double skin wall, devised with great sophistication to enable daylight and solar energy to be used the create the illumination and thermal environment of the building, virtually without mechanical help. Two glass walls were designed, 600mm apart, the outer one being clear, and the inner wall mainly comprising translucent panes, with some clear panes backed by reversible panels, black on one side and polished aluminium on the other. By the manipulation of the components, winter and summer thermal control is provided by the absorption and reflection of solar heat.

The quarter century after the end of the Second World War saw little interest on the environmental potential of the building envelope, other than in the steady creation of propositions by "green" and solar architects. However, by the 1970s, the time of what was known as 'the oil crisis", a new interest was emerging, and a few notable buildings were designed which started to experiment with the potential of the multiple skin. Not surprisingly, in the UK it was Arup Associates, a practice characterised by multidisciplinary design, who produced one of the first noteworthy examples in their ..... at Farnborough ............ Over the following ... years it is possible to identify several hundred buildings worldwide which address the issue of the building facade as though it could operate responsively to changes in the external environment, in the interest of maintaining comfort and acceptable conditions internally, with much less reliance on expensive, and energy consuming, building services. It is in this context that the present design guide is written. Many architects and engineers are devising envelope configurations which claim to resolve issues of environmental design at the buildings surface. Many strategies have been tried, but the field lacks a properly constructed theoretical base.