Robert Lowe

It is a truism that whole energy system models underpin the development of policies for energy system decarbonisation. However, recent reviews have thrown doubt on the appropriateness of such models for addressing the multiple goals for future energy systems, in the face of emergent real-world complexity and the evolution of stakeholder’s priorities. Without an understanding of the changing priorities of policy makers and expectations of stakeholders for future systems, system objectives and constraints are likely to be ill-defined, and there is a risk that models may be inadvertently instrumentalised. Adopting a system architecture perspective, the authors have undertaken a three-year programme of research to explore strategies for decarbonising heat in the UK, with interaction with and elicitation of needs from stakeholders at its heart. This paper presents the procedure, methods, and results of an exercise in which experts from stakeholder organisations across the energy system were interviewed. Analysis of interview data reveals two broad approaches to heat decarbonisation which can be defined as either adaptive or transformative. Specific insights gained from these interviews enabled our modelling teams to refocus their work for exploration with a wider circle of stakeholders. Results suggests that this iterative approach to formalising model-policy interaction could improve the transparency and legitimacy of modelling and enhance its impact on policy making.

It is a truism that whole energy system models underpin the development of policies for energy system decarbonisation. But recent reviews have thrown doubt on the appropriateness of such models for addressing the multiple goals for future energy systems, in the face of emergent real-world complexity and the evolution of stakeholder’s priorities. Without an understanding of the changing priorities of policy makers and expectations of stakeholders for future systems, system objectives and constraints are likely to be ill-defined, and there is a risk that models may be inadvertently instrumentalised. Adopting a system architecture perspective, the authors have undertaken a three-year programme of research to explore strategies for decarbonising heat in the UK, with interaction with and elicitation of needs from stakeholders at its heart. This paper presents the procedure, methods, and results of an exercise in which experts from stakeholder organisations across the energy system were interviewed. Analysis of interview data reveals two broad approaches to heat decarbonisation which can be broadly defined as either adaptive or transformative. Specific insights gained from these interviews enabled our modelling teams to refocus their work for exploration with a wider circle of stakeholders. Results suggests that this iterative approach to formalising model-policy interaction could improve the transparency and legitimacy of modelling and enhance its impact on policy making.

Energy models have been widely applied to the analysis of energy system decarbonisation to assess the options and costs of a transition to a low carbon supply. However, questions persist as to whether they are able to effectively represent and assess heat decarbonisation pathways for the buildings sector. A range of limitations have been identified, including a poor spatio-temporal resolution, limited representation of behaviour, and restricted representation of the full technical option set. This paper undertakes a review of existing energy models for heat decarbonisation in the UK, applying the novel perspective of energy system architecture (ESA). A set of ESA-related features are identified (including evolvability, flexibility, robustness, and feasibility), and models are reviewed against these features. The review finds that a range of models exist that have strengths across different features of ESA, suggesting that multiple modelling approaches are needed in order to adequately address the heat decarbonisation challenge. However, opportunities to improve existing models and develop new approaches also exist, and a research agenda is therefore proposed.

Purpose: Compulsory airtightness testing was introduced for new dwellings in England and Wales in 2006 and in Scotland in 2010 to ensure that they are constructed according to design air permeability targets. These targets are set to limit heat loss through air infiltration. Previous work examining the large Air Tightness Testing and Measurement Association (ATTMA) data set of UK airtightness test data suggested that, in a proportion of dwellings, the targets were being met by post-completion sealing as opposed to airtight construction, but did not quantify the prevalence of this practice. The paper aims to discuss this issue. Design/methodology/approach: In this paper, the distribution of as-built airtightness and the proportion of dwellings undergoing post-completion sealing are estimated from the ATTMA data set covering 2015–2016. This is carried out by Bayesian statistical modelling, using the data set of recorded test results and a modelled representation of the testing process. Findings: This analysis finds the mode of the as-built distribution of air permeability as 4.38 ± 0.01 m³/m²h. It predicts that 39 per cent of dwellings aiming for one of the five most common design targets have sealing interventions at the point of pressure testing to meet their target. The as-built distribution of the ATTMA data is compared to airtightness test data obtained from just before compulsory testing was introduced, showing an improvement in the modal air permeability of 3.6 m³/m²h since testing became mandatory. Originality/value: This paper has investigated the available data beyond simply what is reported, to estimate what the real levels of airtightness in the UK new build stock may be.

This paper brings together a rapid evidence assessment of impacts of elevated CO ₂ concentrations on human cognition with IPCC projections of atmospheric CO ₂ concentration by the end of the present century, and an analysis of potential consequences of increased atmospheric CO ₂ concentrations for ventilation systems in buildings and other enclosed spaces. Whilst only limited research has been done on the effect of CO ₂ on cognition (as opposed to air quality in general), half of the studies reviewed indicate that human cognitive performance declines with increasing CO ₂ concentrations. Hence, given the likelihood of increasing atmospheric CO ₂ concentration by the end of the 21st century, direct impacts of anthropogenic CO ₂ emissions on human cognitive performance may be unavoidable. Attempts to minimise these direct impacts are likely to result in significant indirect impacts on the engineering of ventilation systems and associated energy use in all enclosed spaces including buildings and transport systems. Practical application: This paper concerns what may well be one of the most important long-term drivers of the design, management, operation and regulation of ventilation systems over the remainder of the 21st century. It will be relevant to professionals, particularly at senior levels in the building industry.

Evidence of a fabric performance gap has underlined the need for measurements of in situ building performance. Steady state co-heating tests have been used since the 1980s to measure whole building heat transfer coefficients, but are often cited as impractical due to their 2–4 week test duration and limited testing season. Despite this, the required conditions for testing and test duration have never been fully assessed. Analysis of field tests show that in 12 of 16 cases, a heat loss estimate to within 10% of the result achieved across a full test period can be achieved within just 72 h. These results are supported by simulated tests upon a wider range of dwellings and across wider environmental conditions. However, systematic errors may still exist, even in cases of convergence and cases with significant uncertainties may never converge. Simulated examples of traditional dwellings and those built in line with current building regulation limits may be tested for more than half the year. However, even when simulated with reduced uncertainties, dwellings with low heat loss and high solar gains, such Passivhaus dwellings and apartments, could be successfully tested for just 22% and 12% of a year respectively, demonstrating the limitations of the co-heating method in assessing such dwellings.

Raymond J. Cole’s body of work, spanning sustainable design, system complexity and human agency, has encouraged researchers to reconceptualize the notions of comfort and building performance. However, methods for predicting energy use and assessing environmental performance have remained predominantly within a reductionist approach common to physics and engineering. The recognition that building performance is characterized by interactive adaptivity and co-evolution of the physical with the social has not been matched by the generation of new methods. Although social practice theories that articulate the socio-technical nature of the built environment have been increasingly appropriated to understand occupants’ role in performance, the challenge of studying buildings as complex socio-technical systems remains. This methodological paper discusses the application of the case study method (CSM) to the study of 10 retrofit projects selected from the Retrofit for the Future (RfF) Programme in UK between 2011 and 2012. Guided by Greene’s framework for methodological discourse, the epistemic regime is articulated under four headings: philosophical assumptions, investigative logics, guidelines for practice and contribution to system perspective. The discussion of these domains highlights the fecundity of CSM in providing a more nuanced understanding of the interaction between social and technical systems in performance.

European National Calculation Methods (NCM), such as the UK Standard Assessment Procedure (SAP), are used to make standardised and simplified assessments of building energy performance. These NCMs contain simplifications to aid ease of use and comparability of resulting Energy Performance Certificates (EPC). By comparing SAP with a modern, dynamic modelling system, this study quantifies internal temperatures and thereby heating energy consumption. Results show that for the considered test house SAP results correspond closely to a dynamic model using an idealistic heating system, with perfect control and instant responsiveness. However, the introduction of a dynamic, physically realistic gas fired boiler and water based heating system to the model results in a consistent increase in internal temperature (0.5 °C) and energy demand (by ca. 1000 kWh/a). Variation of further parameters within the dynamic model, controls and heat source size, are presented and compared to SAP results and assumptions. The inclusion of more realistic dynamics in building energy modelling for NCMs may provide a better basis for effective decision making with respect to a wide range of heating systems.

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

From publicly available data, two simple models are developed to help identify the trajectory of total delivered energy to UK households and provide benchmarks for the UK domestic sector. Both models can help to inform policy-makers and the public whether delivered energy in the domestic sector is on track and whether the reductions correspond with the expected impact of a more efficient domestic sector. The annual delivered energy, price, and temperature (ADEPT) model uses multiple linear regression to fit consumption data since 1970 (R ² = 0.76). Findings indicate that with typical recent heating season temperatures of 7°C and at 2005 energy prices, average household delivered energy is estimated at 21.7 MWh (95% confidence interval = 20.8, 22.6). For every 1°C increase in heating season temperature, average household delivered energy drops by approximately 1 MWh/year. Energy price elasticity is estimated at –0.2, so that a 50% rise in energy prices corresponds to an approximate 10% decline in energy demand. To fit quarterly delivered energy data since 1998, a seasonal temperature energy price (STEP) model is also developed using polynomial multiple regression (R ² > 0.99). At 2005 energy prices, the average household has a minimum power demand of 1.2 kW (including approximately 0.4 kW electricity) at about 16°C, which rises as external temperatures drop to 5°C, where it begins to plateau at approximately 3.8 kW. The average heat loss coefficient is estimated at 240–320 W/°C. Both models find no evidence to date to indicate that changes in delivered energy are beyond those expected due to variations in external temperature and energy price. The seasonal model also provides benchmarks for delivered energy as a response to external temperature and energy price that will be useful for a comparison of building performance evaluations with the national stock, without requiring data for a whole year. Deux modèles simples sont développés à partir des données publiquement accessibles afin d'aider à identifier la trajectoire de l'énergie totale fournie aux foyers britanniques et de fournir des données de référence pour le secteur résidentiel britannique. Ces deux modèles peuvent aider les responsables politiques comme le public à savoir si l'énergie fournie dans le secteur résidentiel évolue dans le bon sens et si les réductions correspondent aux effets attendus d'un secteur résidentiel plus performant. Le modèle ADEPT qui prend en compte l'énergie annuelle fournie, le prix et la température utilise une régression linéaire multiple permettant un ajustement des données de la consommation depuis 1970 (R ² = 0.76). Les résultats indiquent que pour des températures types récentes en période de chauffe de 7°C et aux prix 2005 de l'énergie, l'énergie résidentielle moyenne fournie est estimée à 21,7 MWh (intervalle de confiance de 95% = 20,8, 22,6). Pour chaque augmentation de 1°C de la température en période de chauffe, l'énergie résidentielle moyenne fournie baisse d'environ 1 MWh/an. L'élasticité du prix de l'énergie est estimée à - 0,2, de sorte qu'une hausse de 50% des prix de l'énergie correspond à une baisse d'environ 10% de la demande énergétique. Pour permettre un ajustement des données trimestrielles relatives à l'énergie fournie depuis 1998, un modèle des prix de l'énergie en fonction de la température saisonnière (STEP) est également développé en utilisant une régression multiple polynomiale (R ² > 0.99). Aux prix 2005 de l'énergie, le foyer moyen a une demande énergétique minimale de 1,2 kW (dont environ 0,4 kW d'électricité) à environ 16°C, qui augmente au fur et à mesure que les températures extérieures descendent jusqu'à 5°C, température à laquelle la demande commence à se stabiliser autour de 3,8 kW. Le coefficient moyen de perte de chaleur est estimé à 240-320 W/°C. Les deux modèles n'ont constaté à ce jour aucun élément probant pouvant indiquer que les évolutions de l'énergie fournie dépassent celles prévues, dues aux variations de la température extérieure et du prix de l'énergie. Ce modèle saisonnier fournit également des données de référence concernant l'énergie fournie en réponse à la température extérieure et au prix de l'énergie, données qui seront utiles pour comparer les évaluations des performances des bâtiments avec celles du parc bâti national, sans qu'il soit nécessaire de disposer de données pour une année entière. Mots clés: parc bâti parc bâti résidentiel demande énergétique rendement énergétique performance énergétique logement modèles