In the span of two or three short decades, glazed curtain walls and metal panel cladding have become ubiquitous, gracing the skylines of cities as distant and widespread as Chicago, Sydney, London, Singapore, Santiago and Johannesburg. Building designers and the public alike have become used, or we should say addicted, to these types of façades. Yet, there exists a plethora of other materials or systems that can be considered when designing building envelopes, and which offer an incredible array of aesthetics. The latter need to fulfil a variety of functions, including keeping the weather out, ensuring the safety of the public in and out of the buildings, helping achieve a comfortable living and working indoor environment; and much more. When considering a material or system to use in the design of a building envelope, one needs to bear in mind a number of performance requirements.
It thus seems appropriate to carry out a systematic review of the various other façade materials that reside in a designer’s palette, in order to assess the viability of these available choices. As designers, it is absolutely essential that we understand the pros and cons of each alternative, in addition to any possible limitations in terms of their size, availability, formability, cost, etc.
Etymologically, the façade is quite literally the face of the building. It defines its identity, and is often what the public would use to describe or to refer to a specific development. Consequently, the aesthetics of the building envelope is a fundamental aspect to consider. It needs to exhibit flair and refinement. Other than the overall shape of the envelope, which ties with the internal space planning and layouts, the architect should be able to work on qualities such as modulations, texture, colour, reflectivity, gloss level, as well as the possibility to incorporate holes or patterns on the surface for aesthetics, daylighting or natural ventilation. All of these parameters, in conjunction with each other, define the appearance of the building.
Besides the aesthetics, the design team needs to consider the structural aspects of the façade design. The latter needs to be able to withstand wind load, live load, self-weight, seismic loads, snow load, as well as the building movements under various loading conditions, and all of the above should be accommodated for the full lifespan of the building envelope. Several considerations will influence the size of the building envelope framing members, including the type of system, material strength, testing, design code, modulations, loading and floor-to-floor height, amongst others.
Aesthetics alone is not sufficient if the latter does not last for an adequate period of time. The building envelope should be designed using materials and systems that are durable. The façade of a building is susceptible to multiple sources of aggression, including the sun, rain, temperature variations, and other weather conditions. Under the effects of these elements, cladding materials may fade, crack, chip, craze, chalk, debond, warp, become scratched, etc. It should be noted that regardless of how careful one is with the material selection process, no material or system can last for their intended lifespan without proper and regular maintenance.