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Introduction

Modern society is strongly focussed on performance and efficiency. There is a constant drive to make production processes, machines and human activities better, and concepts like high performance computing, job performance and economic performance are of great interest to the relevant stakeholders. This also applies to the built environment, where building performance has grown to be a key topic across the sector. However, the concept of building performance is a complex one and subject to various interpretations. The dictionary provides two meanings for the word performance. In technical terms, it is 'the action or process of performing a task or function'. It may also mean the 'act of presenting a play, concert, or other form of entertainment' (Oxford Dictionary, 2010). Both interpretations are used in the building discipline; the technical one is prevalent in building engineering, while the other one frequently appears in relation to architecture and buildings as work of art (Kolarevic and Malkawi, 2005: 3). But the issue goes much deeper. As observed by Rahim (2005: 179), 'technical articles of research tend to use the term "performance" but rarely define its meaning'. In the humanities, performance is a concept that implies dynamic, complex processes with changing values, meanings and structures (Kolarevic, 2005b: 205).

Whether approaching building performance from a technological or aesthetic perspective, buildings are complex systems. Typically they consist of a structure, envelope, infill and building services. Many of these are systems in their own right, making a building a 'system of systems'. All of these work together to ensure that the building performs a whole range of functions, like withstanding structural loads caused by people and furniture, protecting the occupants from environmental conditions, allowing safe evacuation in case of emergency, delivering a return on investment or making an architectural statement. Building performance thus is a central concept in ensuring that buildings meet the requirements for which they are built and that they are fit for purpose. Building performance plays a role in all stages of the building life cycle, from developing the building brief1 to design and engineering, construction, commissioning, operation, renovation and ultimately deconstruction and disposal.

Different disciplines contribute knowledge on specific performance aspects of buildings, such as architectural design, mechanical engineering, structural engineering and building science.2 Other disciplines focus on specific systems, such as building services engineering or facade engineering, or are grounded in a common method, such as building performance simulation or the digital arts; in many cases disciplines overlap. The knowledge of all these disciplines needs to be combined into a building design, a building as a product and ultimately an asset in operation, which adds further complexities of interdisciplinarity, information exchange, management and control.

Building performance is a dynamic concept. The architectural performance depends on the interplay between the observer, building and context. The technical performance relates to how a building responds to an external excitation such as structural loading, the local weather to which the building is exposed and how the building is used. This often introduces uncertainties when predicting performance. Furthermore building performance needs to materialize within the constraints of limited and often diminishing resources such as material, energy and money. Challenges such as the energy crisis of the 1970s, the concern about climate change and the 2008 global financial crisis all contribute to increasingly stringent targets and a drive towards more efficient buildings and a growing interest in building performance.

Within this context, a large body of literature exists on building performance. Underlying principles are provided by generic books like, amongst many others, Clifford et al. (2009) in their introduction to mechanical engineering, Incropera et al. (2007) on fundamentals of heat and mass transfer, Stroud and Booth (2007) on engineering mathematics, Zeigler et al. (2000) on theory of modelling and simulation or Basmadjian (2003) on the mathematical modelling of physical systems. The application of these principles to buildings and to the assessment of building performance can be found in more specialist works such as Clarke (2001) on energy modelling in building design, Underwood and Yik (2004) on energy modelling methods used in simulation, Hensen and Lamberts (2011) on building performance simulation in design and operation and Mumovic and Santamouris (2009) on their integrated approach to energy, health and operational performance. Architectural performance arguably is covered by Kolarevic and Malkawi (2005) in their work on performative architecture. This is complemented by countless articles in peer-reviewed archived journals such as Building and Environment, Automation in Construction, Energy and Buildings, Advanced Engineering Informatics, Architectural Science Review, the Journal of Building Performance Simulation, Building Research and Information and Design Studies. Building performance is also a day-to-day concern in the construction industry and is of central importance to building legislation.

With the complexity of buildings, the many functions they perform and the multitude of disciplines and sciences involved, there are many different viewpoints and interpretations of performance. The many stakeholders in building, such as architects, contractors, owners and tenants, all view it from a different position. Even in academia, different research interests lead to distinct schools of thought on performance. An example is the work by Preiser and Vischer (2005), who provide a worthwhile contribution on building performance assessment from the point of view of post-occupancy evaluation, yet do not really connect to the aforementioned building performance modelling and simulation domain. This lack of common understanding is problematic as it hinders the integration that is needed across the disciplines involved. It impedes the use of modelling and simulation in the design process or the learning from measurement and user evaluation in practice, since it makes it hard to sell services in these fields to building clients and occupants. The absence of a common understanding also means that building science and scholarship do not have a strong foundation for further progress and that the design and engineering sectors of the building sector are seen to lack credibility.

The discussion about building performance is further complicated by some intrinsic properties of the building sector. Some may consider building to be a straightforward, simple process that makes use of well-tested products and methods like bricks, timber and concrete that have been around for a long time and where lay people can do work themselves after visiting the local builders market or DIY3 centre; however this risks overlooking some serious complexity issues. Architectural diversity, responding to individualist culture, renders most buildings to be different from others and makes the number of prototypes or one-off products extremely large in comparison with other sectors such as the automotive, aerospace and ICT industries (Foliente, 2005a: 95). Typically, buildings are not produced in series; almost all buildings are individual, custom-built projects, and even series of homes built to the same specification at best reach a couple of hundred units. This in turn has implications for the design cost per unit, the production process that can only be optimized to a certain extent and, ultimately, building performance. With small series, the construction sector has only limited prospects for the use of prototypes or the use of the typical Plan-Do-Study-Act4 improvement cycles that are used in other manufacturing industries. Quality control programmes, modularization with standard connectors, construction of components in automated factories and other approaches used in for instance the automotive or electronic system industries are thus not easily transferred to construction as suggested by some authors such as Capehart et al. (2004) or Tuohy and Murphy (2015). Buildings are also complex in that they do not have a single dominant technology. While for instance most automobiles employ a metal structure, building structures can be made from in situ cast concrete, prefabricated concrete, timber or steel or a combination of these; similar observations can be made for the building shell, infill and services. Furthermore the construction industry is typically made up of many small companies who collaborate on an ad hoc basis, with continuous changes in team composition and communication patterns, which are all challenges for the dialogue about building performance. Of all products, buildings also are amongst those that undergo the most profound changes throughout their life; while changing the engine of a car normally is not economically viable, it is common practice to replace the heating system in a building, to retrofit the façade or even to redesign the whole building layout, with profound consequences on the building performance (Eastman, 1999: 27-30). Once buildings exhibit performance faults, these are often hard to rectify;...