Facade Engineering

THE FAÇADE:

 modifies internal environment 

 is related to plant size/ trade off between the two 

 is related to primary structure 

 constitutes appearance of a building 

 is not an afterthought 

 often indicates status of client or building or corporate image 

Credit: Image: Courtesy Shanghai Zendai Bund International Finance Center Real Estate Company Ltd.

ARCHITECT 

It is most likely that the architect’s contribution to the façade is its appearance. Rhythm of mullions and transoms and patterns formed by varying application of glass/ solid infill give what might otherwise be a mundane form texture and scale. Even when architects are fortunate enough to design interestingly formed or massed buildings like Lloyds or Channel 4 the façade is still used to effect the qualities already mentioned. There are, however, other reasons an architect should involve himself in the design of the façade. At a time when there is growing concern about energy usage in construction the façade can be used to modulate natural light availability, passive solar gain and natural ventilation. If used wisely all of these factors can reduce a building’s overall energy requirement-if used unwisely it may do the opposite. If the architect feels competent he might take on the role of façade engineer himself-if not he might employ a façade consultant to help him through the complex minefield that is cladding. It is essential that the architect raises the issue of the façade and at all times keeps in mind what type of façade he has in mind from the earliest design discussions. 

Channel 4 Building, London 1990-4, by Rogers Stirk harbour

STRUCTURAL ENGINEER 

Conversations with the structural engineers should include what type of façade a building is to have should take place from the outset. Façade consultants or persons responsible for the building envelope should be present at the earliest design team meetings. On what false information is a structural engineer calculating primary structure loadings when he does not know what form the cladding or façade will take? An aluminium and glass proprietary cladding system will weigh a lot less than a unitised concrete panel and glass system. This needs to be taken into account when the early structural concept is drawn up. Relief within the depth of the façade may increase or decrease wind loading. Wind loading calculations should be shared information between the façade consultant and the engineer. It may be that a cladding system, for instance structural glazing or concrete panels, may require a form of secondary structure either because extra strength is required or because of tolerances. Main structure deflections can be left high as the fine tolerances involved in a structural glazing system can be accommodated in a secondary system. It may even be that the secondary system can be used in main structural calculations. Glass itself is now considered in structural calculation. 

A solar light collector at the Shanghai World Expo. A stunning example of geometric architecture and technology.

SERVICE ENGINEER 

The type of façade to be used on a building has a direct effect on the form and extent of the servicing of that building. The idea that the façade and the services should be developed in isolation is not sensible. The disciplines cross at many points, not least the following; 

Lighting – if a glass façade is specified on the grounds of increasing daylight or even with the intention of naturally day-lighting an office it must be made clear at the outset how this will work. Management systems that provide no override for users has been proved to be an irritation-these systems are not popular. On the other hand a system with a total override that allows the user to raise or lower blinds 

and turn lights on or off whenever is little more than useless. It has been proved that under these conditions, blinds remain down and lights remain on. The glass wall becomes anything but. 

Ventilation – natural ventilation is probably the most seductive of the energy saving methods but also the most difficult to achieve. Keeping within certain extreme temperatures is what causes the problem. Anyone can naturally ventilate in spring and autumn and keep temperatures reasonably steady; it’s winter and summer that difficulties occur. An all glass façade will only increase the internal temperature of a building thus requiring greater amounts of cooling ventilation. A good relationship between façade engineer and service engineer is vital. 

 

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