WHAT DESIGNERS KNOW
consumption of buildings, for example. Others could calculate the daylight levels or solar gain in rooms anywhere in the world at any time of the year. We could calculate room acoustics and noise transmission. We could estimate the amount of materials required and even the overall capital cost. This would enable us to think about buildings as integrated wholes rather than just as sculptural objects as the CAD modeller does. In fact this vision of the computer as design critic has hardly materialized in terms of the potential because several quite intractable problems have emerged. John Landsdown (1969) first pointed out that we could have software that was ‘ad-hoc’ or ‘integrated’. The advantage with separate and ‘ad-hoc’ programs would be that each requires its own input and the designer would only have to describe to it those features of the building necessary for it to do its limited job. On the other hand an integrated suite of packages could be served by one single comprehensive building model. From the design process point of view the latter seems more desirable as it enables holistic thinking and it has remained the ambition of many software developers to realize it. The first problem is that the time taken to input all this information is such that you can really only afford to do it once the design is pretty well finalized. This too is one of the main obstacles to using virtual reality in design. This then is not computer-aided design but computer-checked design or computervisualized design. The computer is certainly acting as a design critic but rather too late in the process to be constructive.
Conceptual structures The second problem is that when you are designing you need to interact with the representation you are using in a variety of mental modalities (Lawson and Roberts, 1991). Architects it seems unselfconsciously think about their building in several ways while they are designing. Listen to any conversation between architects about buildings that they are either designing or examining and you will hear evidence of this in almost every sentence. They talk about conceptual structures such as spaces, circulation systems or external skins. It is actually very hard to pin down just which physical components belong to these structures and which do not. More problematically the conceptual structures are so organized that any one physical component may belong to many of them (Fig. 6.3). Let us examine this in a little more detail. A building can be seen as a collection of spaces which may be indoors, outdoors or hybrids such as courtyards and atria. Alternatively a building can be seen as a collection of systems such as those for human circulation, those that provide structural stability. There are those that form the external skin or the building core, they may be the collected services for environmental control or for safety and so on. Let us note in passing how complicated this is already since in a framed building a wall may form part of the external skin but not the structure whereas in load-bearing construction it most certainly would. Note also that some internal walls or doors may form part of the fire safety system and others not. You need a great deal of knowledge in order to work all this out, but nevertheless it may be 76