A brief history is provided of models of energy use in the UK building stock, with the focus on the non-domestic sector. This history leads to an account of the development, since 2009, of the 3DStock method for modelling complete building stocks, both domestic and non-domestic. The paper explains how 3DStock models are built and the data sources used. Special emphasis is placed on the relationship of premises (the floorspace occupied by organisations) to buildings. Energy use may be metered at the level of premises, buildings or groups of buildings. Representing the patterns in which premises relate to buildings is therefore crucial to the modelling process, and in particular to the precise measurement of energy intensities. Applications of 3DStock models in building science and policy tools are reviewed, including the London Building Stock Model (LBSM), delivered to the Greater London Authority (GLA) in 2020. This 'digital twin' can be used for the monitoring, simulation and analysis of the building stock. Implications for research and policy are discussed, particularly for energy epidemiology, density, high-rise buildings, retrofit potential, energy-use intensity and benchmarking. Data are in place to extend 3DStock modelling to the whole of England and Wales. Policy and practice relevance The models can be used to assess energy demand in large numbers of buildings in relation to a range of variables, including built form, age, construction and activities. Poorly performing buildings can be identified, and the potential for retrofit-including renewable technology installations-evaluated using the same variables plus information contained in Energy Performance Certificates (EPCs). Policies for addressing fuel poverty can be evaluated by making links to confidential socioeconomic data on occupants. In conjunction with a dynamic building energy-simulation tool, scenarios can be investigated for retrofit, the potential for renewables and issues in demand-side management. Additional uses are in the precise measurements of density and of the three-dimensional character of the urban fabric. There could be applications in public health, the modelling of indoor and outdoor air pollution, and the tracking of material flows. 3DStock models might also be integrated with digital twins of infrastructure systems and networks.

The call for action to transform the built environment and address the threats of climate change has been clearly made. However, to support the development, implementation and on-going evaluation of energy demand policy, a strong evidence base is needed to identify associations and establish underlying causes behind outcomes and variations in end-use energy demand within the population. A new approach to end-use energy demand research is presented which is founded on the interdisciplinary health sciences research framework of epidemiology, along with the establishment of a research centre. A case is made that through an ‘energy epidemiology’ approach a strong, population-level, empirically based research foundation can be advanced. Energy epidemiology is a whole-system approach that focuses on empirical research and provides a methodological framework for building physicists, engineers, sociologists and economists to engage in interdisciplinary work. The adaptation of the epidemiological approach to end-use energy demand studies will provide the means to observe and describe the trends and patterns of energy demand, to undertake and contextualize interventional studies, and to establish strong associations between factors that lead to an energy demand-related outcome or event. Such an approach would strengthen the evidence base to inform policy decisions and evaluate past intervention programmes or regulatory actions. Il a été clairement lancé un appel pour mettre en place des mesures propres à transformer le cadre bâti et à faire face aux menaces du changement climatique. Néanmoins, pour soutenir l'élaboration, la mise en œuvre et l'évaluation en continu de la politique relative à la demande énergétique, il est nécessaire de disposer d'une solide base de données factuelle pour identifier les associations et établir les causes sous-jacentes des résultats et des variations de la demande énergétique des utilisateurs finals au sein de la population. Il est présenté une nouvelle approche pour l'étude de la demande énergétique des utilisateurs finals, qui est fondée sur le cadre interdisciplinaire de l'épidémiologie utilisé pour les recherches dans les sciences de la santé, ainsi que sur l'établissement d'un centre de recherche. Il est fait valoir que, par une approche basée sur une « épidémiologie de l'énergie », il est possible de faire progresser la fondation d'une recherche empirique solide au niveau de la population. L'épidémiologie de l'énergie est une approche systémique globale qui est axée sur la recherche empirique et fournit un cadre méthodologique aux physiciens, ingénieurs, sociologues et économistes du bâtiment afin qu'ils participent à des travaux interdisciplinaires. L'adaptation de l'approche épidémiologique aux études relatives à la demande énergétique des utilisateurs finals donnera les moyens d'observer et de décrire les tendances et les schémas de la demande énergétique, d'entreprendre et de contextualiser des études interventionnelles, et d'établir les associations fortes entre les facteurs qui conduisent à un résultat ou à un événement lié à la demande énergétique. Une telle approche renforcerait la base de données factuelle afin d'éclairer les décisions en matière de politique et d'évaluer les programmes d'intervention passés ou les mesures réglementaires prises. Mots clés: bâtiments, cadre bâti, demande énergétique, épidémiologie, base factuelle, interdisciplinaire, politique publique, recherche

This paper describes the development of a detailed plan to get the social housing stock of the Borough of Islington in London, UK, to net zero carbon emissions. This stock is very diverse in form, age and construction, and includes houses, flats and maisonettes. A total of 4500 buildings containing some 33,300 dwellings were modelled using the 3DStock method. Six packages of measures combining fabric improvements, heat pumps and photovoltaic installations were evaluated for each dwelling individually, in terms of costs, the impacts on gas and electricity use, and predicted cuts in carbon emissions. The rollout of measures between 2020 and 2030 was modelled with a specially developed scenario tool, allowing the user to set different criteria and priorities. Fabric measures on their own were shown to achieve only a 13% cut in gas use on average. Heat pumps are the key to displacing gas use. With all measures combined and taking account of the predicted decarbonisation of the electricity supply, it is only possible to achieve an overall 70% cut in emissions by 2030. Policy relevance The development of a detailed practical plan of action is described: an applied case study with the close engagement of the local authority—not a theoretical desk exercise. Each dwelling in Islington’s housing stock was examined and measured separately. The modelling did not rely on ‘archetypes’ as in many such studies. Realistic retrofit options were analysed in each case, using current cost data from practitioners. The same approach could be applied directly to other London boroughs, and for local authorities outside the capital, although different costs and other local factors would apply. For readers outside the UK, the methodology and tools could serve as exemplars. The findings about the respective contributions of heat pumps, solar photovoltaics and fabric measures, and the effects of different priorities in the rollout of retrofits, have relevance for policymaking more generally at local and national levels.