What is the building envelope? The envelope of the building is the interface between the exterior and the interior. It may be a single plane or layer which we call monolithic (single leaf) or it may have depth and consist of several layers or leaves , hence multi-layered. In a single layer system the external wall must perform all the functions of an envelope including: control of heat and cold transmission (insulation), moisture barrier, ambient and direct daylight transmission, ventilation and/or control of air infiltration and, in the case of fire, smoke and fire protection. In addition, the envelope controls vision to the outside and, in some situations, provides privacy to the inside. Envelopes fall into two main categories: load bearing and non-load bearing. Examples of load bearing envelopes are: i) masonry walls ii) r/c walls iii) framed walls (wood studs or light gage steel iv) other (compacted earth walls, etc.) e.g Exeter Library (L. Kahn): brick and concrete block masonry load bearing exterior wall Examples of non-load bearing envelopes are: i) infill systems ii) curtain walls iii) cladding systems Infill systems, by definition are either in the plane of the structure or behind it. Curtain wall systems hang like a curtain outside the structure. Cladding systems generally refer to solid, non-load bearing surfaces attached to the outside of the structure. There are five possible spatial relationships of the envelope to the structure. This is a result of the development of the free façade by Le Corbusier which proposed the independent relationship between structure and non-structure.
Curtain walls There are two types of curtain wall systems. The “stick” system or post and rail, and the “unitized” system which incorporates prefabricated modules or units. The post and rail (stick) system consists of the vertical framing elements (posts) and the horizontal sub-dividers or rails. They accept panels which might be either glass, solid or mechanical. These panel components are attached to the structural mullions (posts and rails) to form the envelope. This is an on-site activity. The connection of panels to the posts and rails introduces the problem of tolerances. The panel units must fit tight in order to seal the building but they must also be able to accommodate unforeseen movements. The unitized (frame) system is made up of prefabricated façade units. These are factory produced and therefore have a high degree of precision in their design. Unitized envelope components are delivered to the site and attached to the building, usually to brackets that are pre-attached to the building structure. Between units or modules there must be some form of interlock or seal in order to maintain a weather-proof barrier. This is typically accomplished with EDPM (elastic polymer sealant material) strips or with silicon joints. Additionally units often have mechanically interlocking edges. Unitized construction is rapid, which is one of its chief advantages over post and rail.
roof overhang ouvers (brise soleil) greenhouse vented double glazing Control of direct sunlight and the problem of greenhouse heat build-up.
Building Skin Categories Single-skin versus multi-layered: monolithic (one material) or different materials. The different materials may contribute different functions. For example: Multi-layered external wall: a) protected against sun, rain, and wind by a weatherproof membrane with an insulating layer behind. On the interior of the wall lies the finish layer of the space behind which there may be a ventilated space to eliminate condensation. Sun screens such as brise soleil and shutters are an additional layer or shell. An exposed r/c wall with no interior treatment is a rare example of a single leaf, single layer construction. The concrete wall provides all of the functional requirements: thermal protection, water and moisture barrier, control of lighting, etc. In the design of the modern office building the rising demands on comfort and the changing work habits together with the emphasis on lower energy usage are focusing much more attention on the building skin, especially the potential of multi-layered glass facades. See for example Lloyd’s of London (Lecture 8 Pt.2)
Single skin systems Double skin system load bearing non-load bearing
Historical evolution of the modern glass curtain wall. Le Corbusier Maison Dom-Ino Housing Support System 1918-1922
The Five Points (of a new architecture). LeCorbusier 1927
<ul><li>Le Corbusier in the 1920’s </li></ul><ul><li>Villas in Paris (Villa LaRoche, Villa Cook, Villa Plainex, Villa Meyer, Villa Stein, Villa Savoye </li></ul><ul><li>Used the Domino frame concept and demonstrated the architectural potential of the five points. </li></ul><ul><li>Private residences on infill sites in Paris (LaRoche, Cook, Plainex) and free-standing ‘villas’ in the suburbs (Stein & Savoye) </li></ul><ul><li>Seen not as isolated detached villas but as typological units in mass housing projects for his urbanism projects (City of three million and Ville Radiuse). </li></ul><ul><li>Machine aesthetic. Embraced ‘image’ of technology but employed traditional methods of construction. </li></ul><ul><li>Used traditional methods of heating (steam radiators). Houses ventilated in typical fashion with operable (sliding) windows. </li></ul><ul><li>Addressed daylighting / natural light effectively via structural and envelope design. Incorporated electric lighting but not as an integrated design element. </li></ul>
League of Nations International Competition Entry Le Corbusier Geneva, Switzerland 1929
Details of enclosure proposed by Le Corbusier. On the left, description of a window washing machine, a new concept devised by Le Corbusier. On right, the section showing layers of construction of the exterior wall: operable windows, shading devices, and a rainwater gutter integrated with retractable exterior sun shades.
Salvation Army Building, Paris 1928 - 1932 Le Corbusier Salvation Army Building (Armee’ de Salute) Le Corbusier Paris 1932
Salvation Army Building after addition of new brise soleil. Salvation Army Building ca. 1934
Factory Building in Eastern France Le Corbusier St. Die, France ca. 1946
Unites des Habitation Le Corbusier Marseilles, France 1946-52
Monastery of La Tourette Le Corbusier Eveux-sur-l’Arbresle, France 1953-60
Palace of Labor P. L. Nervi Turin, Italy ca.1962
Willis Faber Dumas Corporate Headquarters Foster and Associates Ipswich, England 1982?
Sainsbury Center for Visual Arts Norman Foster Norwich, England 1978