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  • Giacomo Chiarani


Updated: Feb 26, 2021


The books that provided the basis for the development of a theory in this research are, among others, Reyner Banham’s The Architecture of the well-tempered Environment (1969) and The Selective Environment by Dean Hawkes et al. (2002) This research owns many concepts to these books but at the same time it aims to explore their limitations.

Banham introduces a significant distinction between environmental typologies of control. He distinguished three categories: conservative, selective and regenerative. As Hawkes underlines in the book "The Environmental Tradition” (1996), Banham is not critical in the adoption of one mode or another, but he describes the relation between modes of controls and architecture, although not in terms of user active-passive control. Banham looks at the relation between exposed controls (power, selective, conservative) and the architectural language generated by them. In his analysis there is no qualitative difference between Piano’s Centre Pompidou and the St. George ’s School by Emslie A. Morgan. However from the user control perspective these two buildings are very different. Piano’s building employs mechanical air conditioning and the design is not related to environmental considerations. Users have no control and in terms of user-facade interaction the role of user is very passive.

On the other hand the St. George’s School uses a manual control of ventilation and solar radiation control. The south facade includes a ‘solar wall’, that consists of two layers of glass separated by a space to shed a diffused light into the teaching areas. (Banham, 1969, pp. 281) Users can control ventilation by openable windows. These include opaque panels, painted black on one side, polished aluminium on the other. According to the season, users reverse these panels to reflect or collect solar radiations. What can be criticized is the idea of full control that can be, according to Banham, achieved only by mechanical means (where user have low control over it). This is not the case. Selective buildings with high user control of the facade demonstrate that a “full control” can be obtained with a high user-facade interaction. His vision of technological progress is more a Positivist vision than a punctual analysis of user-machine interaction.

Dean Hawkes re-interprets the concept of Banham’s selectivity and focuses on selective design. For Selective design, Hawkes, refers to buildings whose form is justified by climatic considerations. Hawkes’ selective design is based on the view of a building as a system of interacting elements: the form, the fabric, the materials, the mechanical system and the control that operate upon them. (Hawkes, 2002, pp. 31)

The selective building for Hawkes, responds over seasonal and diurnal variations of solar radiation, temperature, humidity, wind speed and direction, variation of daylight. But It is not clear in Hawkes what is the relation between user control and selective design. This research analyses not the interaction of all the elements but the interactive portion that interests the user and the control of facade. This assumes a great importance in the design of selective buildings.

It is important to underline that in this research the term selective facade differs from the term interactive facade. While for Hawkes the terms interactive facades and selective facades are synonymous, since they both refer to the interaction between form and climatic responsiveness, in this research the term Interactive facade refers to the user-facade interaction. Therefore it is not always the case that interactive facades are selective facades, or vice-versa. There are cases in which users have low control but the facade can be named climatically responsive. For instance, Le Corbusier in Chandigarh employs fixed brise-soleil and natural ventilation to control solar radiations and humidity. Here users have a passive interaction but the facade has a good capacity to respond to climatic variations. Dean Hawkes points out that in the selective design, control is by occupants, that environmental control may be a combination of automatic and manual means and that exclusive mode is automatically controlled and is predominantly artificial (Hawkes et al., 2001, pp. 7). It is possible to demonstrate that, for instance, self-learning (artificial intelligent) facades operate autonomously by climatic sensors without any user intervention. Although the control is automatic they are selective facades. The facade of the Secretariat in Chandigarh controls the solar radiations and users have no manual or automatic control. They have a passive interaction with the facade while the facade have a passive interaction with climatic variations. The concept of “active” and “passive” in relation to the control of the environment has been marginally studied by Dean Hawkes in his book The Selective Environment. Dean Hawkes points out that occupants have an important role in achieving standards of comfort. In addition, this condition brings an interaction between the building and the occupants.

“The idea of selective design rests upon the understanding of a building as a system of interrelated and interacting elements. The form, fabric, materials, mechanical systems of a building, and the controls that operate upon them are located within naturally occurring climate with all of its seasonal and diurnal variations of solar radiation, temperature, humidity, wind speed and direction, variations of ambient light, so forth.” (Hawkes et al., 2002, p.31) In Hawkes’s words, selective buildings are interactive buildings; materials, fabric, mechanical systems and the control that operate upon them are all interactive elements. As Hawkes points out, selective buildings are in opposition to exclusive buildings. A superficial distinction is that the former refers to buildings that use ambient energy sources for the creation of natural environments while the latter refers to buildings that use predominantly mechanical plant to create controlled, artificial environments (Hawkes,D., 1996, p.14-15).

What is more interesting is Hawkes’ idea of selective interaction between building and environmental control. Although the idea of selective design has its origin in Olgyay’s pioneering work and Reyner Banham ‘s seminal account of The Architecture of the Well-Tempered Environment, Hawkes’ conception is profoundly different to Banham’s. In Banham,

selective mode employs structure not just to retain desirable environmental conditions, but, to admit desirable conditions from outside. Thus a glazed windows admits light but not rain, an overhanging roof admits reflected sunlight, but excludes the direct sun, a louvered grille admits ventilating air but excludes visual intrusions. (Banham,R., 1969)

On the other hand Hawkes introduces the question of occupant control. For him, not only the building is employed in a selective mode, but the occupant cooperates with the building in order to filter the natural environment as a first step in the process of adaptation (Hawkes, 2002, p.vii). As Hawkes underlines, many selective buildings make some use of a mechanical plant in achieving acceptable standards of comfort. However, the relationship between the building and the plant is different in exclusive buildings.

“One of the fundamental conceptual shifts in the development of the exclusive mode was the assumption that the plant was a primary agent of control. In selective design, auxiliary systems should be regarded as secondary to the environmental function of the fabric”. (Hawkes et al., 2002, p.13).

For Hawkes, the intervention of occupants in order to adjust the fabric, by opening windows, drawing blinds and by their operation of plant, setting the heating control, switching lights, is a defining characteristic of a selective building. This research, dissimilarity from Hawkes’ doesn’t aim to study the difference between selective and exclusive modes, but the way they establish an interaction with occupants. In particular it aims to understand the relation between different “users controls modality” and different grade of responsiveness of facades. The following diagram summarises the difference between interactionism and Hawkes’s selective environment. It is adapted from Scott Murray’s interpretation of James Fitch’s idea of building envelope as selective filter (Murray, 2009) and the idea of selective environment by Dean Hawkes.

(adpted from James Martson Fitch, Dean Hawkes and Scott Murray)

The selective facade (at the centre) is a generic climatically responsive facade. On its right the external environment. On the left side is a user who, with the facade represents the user-facade interaction. On the right side is the external environment with its seasonal and diurnal climatic variations. These include four categories of variations: thermal (winter-summer temperature and humidity; wind direction; solar radiation); water proof (rain); air quality (fresh air, control of unpleasant odours, control of dust and pollution) visual (provide and control daylight, control of glare). All these elements are points of control that user or the facade have to manage in order to be responsive to climatic variations. The left side of the diagram is the user-facade interaction (interactionism) and the right side is the selective environment. In the former the attention is paid on the interaction between user and facade where the active or passive role of users affects the nature of selective facades; in the latter (Hawkes) the focused area is on the relation between climatic variations and facade where users are the final judges of the environment comfort that is characterized by the selective design-climate relationship.

The concept of facade and user control in this research uses as starting point the Dean Hawkes’ theory of environmental control’s evolution. He schematises the development of environmental control through four diagrams. The first is called minimal system (Fig.1). It is a loop system in which D are the environmental disturbances, C is the set of physiological variables which determine the person’s state of comfort, N is the channel through which the disturbances are transmitted to the physiological variables and is in effect a combination of the physical environment and the individual’s physiology. According to his diagram, P represents the variables like geographical location and body posture. In this minimal system the term Ro represents the control of these variables. This simple diagram represents the human control of an environment. At this stage Hawkes doesn’t include any architecture or built environment. It could represent a naked person in an open environment like a park or a street. Hawkes suggests that a person interacts with his/her generic environment by N, which is an interaction between the physical environment and the individual’s physiology. The second diagram (Fig.2) represents the environmental control augmented by clothing and building fabric that Hawkes associates to the primitive hut and the adoption of clothing. Hawkes adds a number of letters: F is the filter. He describes F as the fabric of the building; I is a description of the internal environment; N becomes N’ to indicate the effect of clothing and P’ are the results of variability of both clothing and building fabric. In this diagram, as indicated by the absence of the arrow between C and Ro, occupants have not control of the environment. The variables of building envelope and clothing represent the only way to gain a control of it. Hawkes points out that, in an evolutionary account the benefits of shelter are soon augmented by the introduction of “plant”, M. In this third diagram (Fig.3) P’ is substituted by P’’ and is subjected to regulation by occupants. This means that occupant have control over fabric and mechanical plant. The final scheme (Fig.4) represents the buildings in which plants and fabric are automatically controlled. Hawkes explains clearly the nature of building-user interaction in terms of environmental control. However, his historical simplification of the evolution of environmental architecture doesn’t include any architecture in which no mechanical plant is employed but occupant control of the fabric by, as Hawkes’, Ro. What Hawkes’ lacks is a diagram that shows the relation between control, occupant dimension, the environment and the building after the primitive hut and before the deployment of plants. This typology represents a crucial aspect in the evolution of environmental control strategies. The relation between occupant behaviour and environmental control is analyzed in Hawkes’ only in function of the achievement of human comfort and not as driver in the development of environmental control strategy.

Dean Hawkes, Environmental control, minimal system. (Hawkes, 1996, p. 29)

Dean Hawkes, Environmental control augmented by clothing and building fabric.

(Hawkes, 1996, p. 30)

Dean Hawkes, Environmental control augmented by clothing and building fabric.

(Hawkes, 1996, p. 31)

Dean Hawkes, Environmental control augmented by clothing and building fabric.

(Hawkes, 1996, p. 30)

(Drawing by the author) Diagram of Interactionism following the idea of selective environment of Hawkes. Interactive facades (IF) are the modifier but also the element around which the building-user interaction is filtered. N’ is the channel between external

and internal factors influence the human behaviour and consequently the achievement of

user comfort.

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