Towards the sustainable city

Renewable Energy, Vol, 6, No. 3, pp. 345-352, 1995

Pergamon 0960-1481(95)00011-9

Elsevier Science Ltd Printed in Great Britain 0960-1481/95 $9.50 + 0.00

TOWARDS THE SUSTAINABLE CITY DEAN HAWKES Department of Architecture, University of Cambridge, Cambridge CB2 1PX, U.K.

ABSTRACT This paper presents a selection of architectural design projects produced since 1983 by the practice of Stephen Greenberg and Dean Hawkes. Each of these, in some way, incorporates aspects of the research into low-energy design which has followed the increase in energy costs which occurred in the early 1970s. The aim of the paper is to show how these individual projects may be seen collectively as elements of a low-energy city, or as steps towards the idea of a sustainable city. The paper develops a critique of this proposition and concludes with a speculation about the nature of the truly sustainable city. KEYWORDS Architecture; Energy; City; Sustainable. INTRODUCTION In considering the contemporary city a distinction may be made between domestic and nondomestic buildings (Penz, 1983, Duncan & Hawkes,1983). The prospect of mixed-use buildings in which people both live and work has many attractions, both socially and architecturally, but, particularly in the U.K., these are the exception rather than the rule. In,the work of my practice with Stephen Greenberg between 1983 and 1994, we carried out a number of projects, built and unbuilt, in which we attempted consistently to apply the fruits of research into low-energy design. These have been for both domestic and non-domestic uses and, whilst they are not representative of all possible building types, are sufficiently diverse in their situations, scale and uses to allow us to construct a schematic representation of the nature of a low-energy city. In three broadest terms our approach to energy-saving design in the work of the practice has had its roots in the tradition of Olgyay's Design with Climate (1963) and with its more specific and recent manifestation as passive solar design. In theoretical studies in the 1980s I proposed a distinction between two modes of environmental control in buildings, the exclusive and the selective modes (Hawkes, 1981). The salient features of these are summarised in Table 1.

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D. HAWKES Table 1 General characteristics of exclusive and selective mode buildings. .

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EXCLUSIVE

SELECTIVE

Envitvmment is automatically controlled and is predominantly artificial.

Environment is controlled by a combination of automatic and manual means and is a variable mixture of natural and artificial.

Shape is compact, seeking to minimise

Shape is dispersed, seeking to

the interaction between exterior and interior environments.

maximise the use of ambient energy.

Orientation is unimportant.

Orientation is crucial.

Windows are restricted in size.

Windows are larger on southerly facades than to the north. Solar controls required on south-facing windows.

Energy sources are primarily

Energy is a combination of ambient

generated and are in use all year round,

and generated. Use varies seasonally and buildings are 'free-running" for much of the year.

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DOMESTIC BUILDINGS Our first commission in the practice (Fig 1) was for a house on an infill site in a Bloomsbury mews in central London (Macleod, 1985). Within restricted boundaries the house uses a small atrium as a major element in its environmental and energy strategy. This brings daylight to the depth of the plan and, by acting as a buffer space, achieves a low heat requirement. The house is a specific response to the needs of a particular client on a unique site. It does, however, suggest a generic solution to the problem of the small urban dwelling in the manner in which it addresses the need to provide daylight and solar warmth in densely (Fig 2) developed sites. The house, which won an RIBA Architecture Award in 1987, was later extended to provide further domestic accommodation and a photographic studio (Darley, 1991). In achieving this a similar set of principles was applied, as they also were in two houses for a speculative builder on a site in north London (Fig 3). In 1986 we designed a house for a site in Cambridge (Cruickshank, 1987). In the more open conditions of a suburban site we were able to apply the principles of classical passive solar design (Fig 4). The house which was not built was also to be an exercise in high insulation construction by the use of a prefabricated timber-frame system imported from Scandinavia. This also incorporated a heat-recovery system. Similar themes were applied in the design of another house for a Cambridge site which was built in 1991 (Architecture Today, 1993). Here a small infill site is occupied by a single story structure in which the principal living room has a tall south-facing bay window which acts as a direct-gain collector and which, by virtue of its height, allows the capture of low-angle winter radiation (Fig 5). The construction, of twoleaves of insulating blockwork with an insulated cavity, has a U-value of less than 0.2w//sq.m./deg.C. The spatially complex living room is, in addition, an experiment in the idea of spatial and temporal diversity of environment. With the freedom which is offered in the domestic situation it is possible for the occupants of the room to move into or out of the direct gains to seek warmth or cool as they and the seasons desire or dictate. On a clear, cold winter's morning the bay window is a perfect location for a passive solar breakfast and on a hot summer's afternoon the cool inner part of the room provides refuge. This principle is further developed in the highly insulated 'box' of the study wing which can become the

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principal heated space on cold winter's evenings if the greatest economy is required. This house won an RIBA Architecture Award in 1992. A domestic project of a different order is the restoration and enlargement of the Principal's Lodge at Newnham College, Cambridge completed in 1993 (Fig 6). The original lodge, built in 1958, had an open central courtyard surrounded by two-story high single glazing. This led to serious environmental problems, of summer overheating and winter chill and consequential energy penalties. We calculated that the building could suffer peak solar gains through the courtyard glazing of the order of 40kW and heat losses, under standard steady-state design assumptions of up to 17kW. Our solution was to cover the courtyard with a roof containing a large lantern light. This provides sufficient daylight for a wide range of activities from college meetings to lectures and musical recitals. By using a high standard of thermal insulation, less than 0.2W/sq.m/deg.C.,the heat loss through the central space is reduced to less than 3kW. The remotely operated clerestory opening-lights provide stack and wind assisted ventilation which, combined with the substantial reduction of solar gains, ensures effective temperature control in summer. NON-DOMESTIC BUILDINGS In 1985 we made a design for a speculative office building, on a site on the banks of the River Ouse at York, as an entry in an open architectural competition (Fig 7). Our scheme, which was commended by the assessors (Architects'Journal, 1986) made use of simple principles of atrium design to provide a well-controlled environment at minimum energy cost. As is the case with most of these projects the design attempted to make a generic proposition about the problem of the low-energy urban building and we demonstrated that the principles upon which it was based could, in certain circumstances, be applied to urban retrofit as effectively as to the design of new buildings (Baker & Hawkes, 1987). In an actual retrofit project of a highly specific nature, the reconstruction of the North West Reform Synagogue in London, 1987-88, the same environmental and energy-saving principles were applied (Architects'Journal, 1989). By concentrating upon the provision of good standards of daylight, for both secular and sacred spaces, by careful orientation of openings and the arrangement of new spaces relative to existing structures, the energy efficiency of the building was substantially improved whilst the architectural quality, particularly of the sacred sanctuary, was enhanced (Fig 8). The project, not now to be executed, was selected, in 1992, by the Venice Biennale for inclusion in its exhibition, Architecture and Sacred Space. In 1989 we received a commission to build the Friary Project at Maldon in Essex. This provides accommodation for the County Library, offices for the administration of social services in the town, and a day-care centre for the mentally-handicapped. Our design consists of two buildings located in the conservation area of the historic town centre (Fig 9). In both the general principles of 'Selective' design were applied with a clear distinction being drawn between the design of north and south facades, daylighting standards operating as primary generators of both form and detail, and responsibility for the control of the environment being given to the users (Hawkes and Steemers, 1991). In considering the wider architectural question of building in historic centres, we have argued that these principles allow the reestablishment of the underlying environmental factors, of natural light and natural ventilation, which profoundly influenced the nature of historic buildings, before the caesura caused by the introduction of mechanical services systems in 'Exclusive' designs (Greenberg and Hawkes, 1991). The buildings were completed in the autumn of 1993 and first evidence suggests that they have met with wide approval by their users (Nikolopoulou, 1994).

BEYOND THE STATUS QUO The characteristics of these projects are by no means unique. The work of a growing number of architects adopts the same or similar principles to produce buildings which achieve useful

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energy savings when compared to conventional designs. When these buildings are considered collectively, however, they offer and indication of the nature of a transformation of the city which would represent a step towards the realisation of the idea of the Sustainable City. If the overall energy demand of the building stock could be reduced by the order of the 30% which designs such as these can achieve this would be a valuable beginning to the process. These designs are the status quo. The problem is, however, that this would only represent a small evolutionary step. As the evidence of the biological sciences demonstrates, however, nature, when confronted by extreme problems, is capable of evolutionary strides of great length. In his review of the outcome of the U.S. Department of Energy's National Solar Energy Program, 1975-1986, Anderson (1991) observed that, "...the amount of renewable energy that impinges on buildings is well in excess of the energy needed. Yet only a small fraction of that energy is being tapped by even the best of solar buildings. If buildings could be clad in advanced materials and systems that could more fully convert and use that natural energy than today's techniques are capable of doing, then there would be energy to spare, buildings would no longer be energy 'consumers' but might rather be considered energy 'producers'. If we extend this proposition from the scale of the individual building to that of the whole city an astonishing prospect opens up. For the first time in many centuries the city could be totally self-sufficient in energy and could even become an exporter of energy to its hinterland. One of the seminal documents in urban theory is yon Thunen's The lsolatedState , published in 1826 (fig 10). In this he proposed a model of land use for an ideal, self-sufficient city. This consists of a series of concentric circles of different land uses whose position relative to the centre is determined by an economic calculation of land and transport costs and the value to the city of the commodity produced. The first of these circles is allocated to horticulture and dairying, but, of particular significance in the present discussion, comes sylviculture, the growing of trees. This is the energy source of the city. As cities expanded in the 19th century so they became dependent upon more distant energy sources and, with the arrival of the railways, it became possible to transport fossil fuels economically over great distances and the city's 'energy hinterland' began to expand. The modern, city, with its concentration of energyconsuming buildings, now depends on an international hinterland in which enormous quantities of non-renewable fuels are transported over great distances to be consumed either directly in the buildings or to be delivered to power stations for conversion to electricity and, thence, through a grid distribution system, to the cities and their buildings (Fig 11 ). The transformation of the city from 'consumer' to 'producer' of energy would be an enterprise of enormous magnitude. It would require the commitment of resources of all kinds at a level which has never before been applied in the field of building and urban development. My aim in raising the prospect is primarily rhetorical. But, from time-to-time, it is necessary to look beyond the kind of everyday practice described above, and of correspondingly everyday research, to establish the long term agenda. The spectacle of the modem air-conditioned, glasswalled office building visibly consuming energy to reject energy demands ambitious action. Speaking at the Convention of the Royal Incorporation of Architects in Scotland in 1993, the distinguished Italian architect, Giancarlo di Carlo said, "Once we produced to consume, now we consume to produce." The sustainable city would be the major instrument by which we could return to that condition. REFERENCES Anderson, B. (199l) Solar Building Architecture, MIT Press, Cambridge, Mass. Architects' Journal (1986) York Riverside Competition, A J, 16,4.1986. Architects' Journal (1989) Creative Adaptation, AJ, 1.2.1989. Architecture Today (1993) Hawkes House, Cambridge, A T, April 1993.

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Baker, N. & Hawkes, D. (1987) 'Glazed courtyards: an element of the low-energy city', in Hawkes, D. et al (eds) Energy and Urban Built Form, Butterworths, London. Cruickshank, D. (1987) 'Proportional Representation', in Architects'Journal, 18.2.1987. Darley, G. ( 1991) 'Three into One', in Architects'Journal, 26.6.1991. Duncan, I. & Hawkes, D. (1983) Passive Solar Design in Non-Domestic Buildings, Martin Centre Report to the Energy Technology Support Unit, Harwell, June 1983, Ref. ETSU S-I110. Greenberg, S. & Hawkes, D. (1991) 'Towns and People: the Friary Project', in Architecture Today, June 1991. Hawkes, D. (1981) 'Building Shape and Energy Use', in Hawkes, D. & Owers, J. The Architecture of Energy, Longmans, London. Hawkes, D. & Steemers, K. (1991), 'Research into Practice: a case study in the application of technical studies in architectural design',in Renewable Energy, Vol. 1, No.3/4, 1991. Macleod, R. (1985) 'Infill House in Bloomsbury', in Architects'Journal, 30.10.85. Nikolopoulou, M-H (1994), Human Comfort and Occupants'Interaction, M.Phil dissertation Department of Architecture, University of Cambridge (unpublished). Olgyay, V. (1%3) Design with Climate, Princeton University Press. Penz, F. (1983) Pct~'siveSolar Heating in Existing Dwellings, Martin Centre Report to the Energy Technology Support Unit, Harwell, November 1983, Ref ETSU S-1056a.

Figure 1 Mews House, Bloomsbury, London, Phase One 1983-85 Cross-section

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Figure 2 Mews House, Bloomsbury, London, Phase Two, 1987-90 Cross-section

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D. HAWKES

Figure 3 Houses, Camden Mews, London, 1986-88 Plan and cross-section

Figure 4 House at Storey's Way, Cambridge, 1986 Cross-section I

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Figure 5 House at Gisborne Road, Cambridge, 1990-91 Plan

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Figure 6 Principal's Lodge, Newnham College, Cambridge, 1991-93 Cross-section

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