**2. Sustainable design: from buildings to the city**

influence of the urban form on local microclimate.1

38 Sustainable Urbanization

overall performance.

1

(UK).

arranged on a site heavily affects their owners' energy performances and environmental behaviours. The growing awareness of these issues is gradually attracting the attention of both international organizations and international researchers towards the urban dimension (urban block or district), thus broadening the field of architectural interventions. In this light, urban design, which lies in‐between urban planning and architectural design, has become the appropriate tool through which to operate in achieving sustainability's goals. This recommen‐ dation, however, is not novel. In 1976, the European Commission suggested it during the first United NationsConference on HumanSettlements, 'Habitat' (Vancouver), in whichthe 'design of human settlement' was recognized as a strategic matter in contrasting the «social, economi‐ cal, ecological and environmental deterioration» of urban areas [1]. Nevertheless, the latest 'sustainable urban design' seems to increase its own complexity due to the involvement of different interrelated disciplines, such as fluid dynamics, climatology, technical physics and computer engineering. This interdisciplinary perspective demands updates to the design processinordertoincorporateexternalcontributionswhilemaintainingarchitectureattheheart of the process. In particular, both environmental data and analyses need to be reintegrated into the urban project from the design's initial phases. In fact, this has been an ordinary considera‐ tion in the history of architecture, in which several pieces of historical evidence prove in a clear waythein‐depthrelationshipbetweenurbanformandlocalclimaticconditions.Examplesoccur throughouthistory,startingfromvernacularsettlementsuntiltheModernMovement'smasters, and most of the 'environmental' knowledge of past designers is also stated in important recommendations contained in ancient manuscripts (Vitruvius, Aristotle, Varrone, Columel‐ la, Palladio, etc.). Nevertheless, most of the established abilities have been forgotten in favour of building technology systems, with an illusory belief in their supremacy. The energy and environmental crises of the 1970s clearly displayed their failure, encouraging designers to rediscover projects' environmental components as a function of a sustainable future. In this light, the past's lessons on 'sustainable practices' have grown in importance, especially when coupled with scientific and informatic progress. Computer advances, in fact, make it possible to study increasingly broad areas (CitySim, ENVI‐met, Virtual Environment) and contribute to supporting urban design's processes with environmental analysis software. The latter acts as useful'feedback'tools,abletoverify(qualitatively)theenvironmentalbehaviouroftheproject's concept by taking into account different climatic data (airtemperature,relative humidity, wind velocity and main directions, etc.) and form parameters (sky view factor, aspect ratio). In this way, designers experiment with a new methodology in the project's development, one that allows them to evaluate the initial urban proposal and, gradually, to modify it in relation to the main criticalities that emerged from previous environmental analyses' results. Nevertheless, modifications must respect a project's fundamentals and collaborate in the improvement of its

 Examples are the Martin Centre for Architectural and Urban Studies of Cambridge; the 'Urban Physics' research group (ETH, TU Delft and Cypro University); the Centre for Advance Urbanism and the SENSEable Lab of MIT; the Harvard Centre forGreenBuildingsandCitiesandtheCityFormLab;theEPA'sEPFLSolarEnergyandBuildingPhysicsLaboratory (Luisanne); the Environment People and Design (ePad) Research Group in Nottingham (UK); the Berkeley's Center for Environmental Design Research (U.S.A.) and the UCL-Institute for Environmental Design and Engineering in London

In fact, the way in which buildings are

As stated above, the relationship between a building and its context has a heavy influence on both local microclimatic conditions and a building's energy‐environmental impact, shifting designers' and planners' attention from buildings to the block dimension. The urban structure substantially affects a building's access to sunlight and ventilation, defining its capability to exploit passively the heat produced by solar radiation on vertical surfaces, the natural daylight and ventilation of inner spaces, as well as the reduction in environmental and noise pollution. The necessity of this 'change of scale' has been affirmed, in the last few years, in several national and international scientific works, in which authors highlighted the achievable benefits both in relation to climate change goals and energy issues. Among the most significant attestations, the U.S. Green Buildings Council stated that the neighbourhood level was «the primary scale at which building professionals can begin to address impacts of climate change». In fact, «the design and pattern of neighbourhoods […] play an important role in amplifying or dampening climate effects» [2]. Evidence of this is the Urban Heat Island phenomenon (UHI), fostered by cities' higher densities and the *albedo* properties of common urban materials, and the more frequent extreme weather events, such as flooding, strengthened by urban pavements' waterproofing and inadequate storm‐water runoff.

Furthermore, in relation to the energy issues, several pieces of national and international research supported the block dimension as the only possible way to decrease buildings' consumption and, therefore, to improve their environmental impacts. A recent study by Hachem, Athienitis and Fazio [3] showed how different layouts of the same building typology (terraced houses) modify their energy consumption, increasing their values between +6 to 8 and +25%. Orientation and buildings' arrangements are considered central in the project's process by its authors, conferring on the initial phase of the design huge energy responsibilities, which were estimated as being between 65 and 85% of successive building energy demands.

<sup>2</sup> The International Congress of Modern Architecture focused on the work of Hannes Meyer, Mart Stam, Walter Gropius, Erns May, and Alexander Klein on *Existenzminimum* ("minimum dwelling"), aimed at reducing building costs (including the cost of land consumption) by a reduction of the worthless surfaces of houses. Research on typology reached some standard formulations of the new working-class building environment, in which the amounts of daylight, fresh air, heat, and silence were radically maximized.

The results of this study are comprehensible in relation to the microclimatic consequences of different buildings' arrangements. The influence of the modification of urban geometry on the urban microclimate was well known until the 1970s, in the main works of the climatologists T.R. Oke [4] and H. Langsberg [5], which became the theoretical basis of reference for most of the successive work on environmental design. As stated by Givoni in 1989 [6], and reported later in Steemers' and Ratti's work [7], the influence of climatic change on outdoor temperature, solar radiation and wind speed, caused «by 'the structure' of the city […] result in modified energy consumption». An urban grid's orientation, density and a building's typology heavily influence the wind pattern and the solar access in urban areas, while also defining the microclimatic conditions of outdoor and inner spaces. Further significant studies on the energy and environmental 'costs' of urban form have been developed during the last few years by several scholars (K. Steemers [7–10]; V. Gupta [11, 12], R. Compagnon [13], R. Knowles [14], E. Ng [15, 16], F. Allard [17, 18] and B. Blocken's research group [19, 20], including J. Carmeliet and M.K.A. Neophytou [21]).

Interest in this 'change of scale' in sustainable design is slowly extending from scientific research into concrete actions. In 2010, the European Commission introduced the *Advisory Group ICT Infrastructure for Energy‐Efficient Buildings and Neighbourhoods for Carbon‐Neutral Cities* [22] and, in June 2014, the European Urban Knowledge Network (EUKN), together with the Cellule Nationale d'Information pour la Politique Urbaine (CIPU), presented the *Certifi‐ cation Systems for Sustainable Urban Neighbourhoods* «as tools to evaluate and maintain high quality standards in urban development» [23]. Although practical initiatives are still few in number, they clearly envisage architects and planners' future goals.
