A New Generation of Thermal Energy Benchmarks for University Buildings

In 2008, the Chartered Institution of Building Services Engineers (CIBSE TM46 UC) presented an annual-fixed thermal energy benchmark of 240 kWh/m2/yr for university campus (UC) buildings as an attempt to reduce energy consumption in public buildings. However, the CIBSE TM46 UC benchmark fails to consider the difference between energy demand in warm and cold months, as the thermal performance of buildings largely depends on the ambient temperature. This paper presents a new generation of monthly thermal energy benchmarks (MTEBs) using two computational methods including mixed-use model and converter model, which consider the variations of thermal demand throughout a year. MTEBs were generated using five basic variables, including mixed activities in the typical college buildings, university campus revised benchmark (UCrb), typical operation of heating systems, activities impact, and heating degree days. The results showed that MTEBs vary from 24 kWh/m2/yr in January to one and nearly zero kWh/m2/yr in June and July, respectively. Based on the detailed assessments, a typical college building was defined in terms of the percentage of its component activities. Compared with the 100% estimation error of the TM46 UC benchmark, the maximum 21% error of the developed methodologies is a significant achievement. The R-squared value of 99% confirms the reliability of the new generation of benchmarks

A comparative study of benchmarking approaches for non-domestic buildings: Part 1 – Top-down approach

Benchmarking plays an important role in improving energy efficiency of non-domestic buildings. A review of energy benchmarks that underpin the UK’s Display Energy Certificate (DEC) scheme have prompted necessities to explore the benefits and limitations of using various methods to derive energy benchmarks. The existing methods were reviewed and grouped into top-down and bottom-up approaches based on the granularity of the data used. In the study, two top-down methods, descriptive statistics and artificial neural networks (ANN), were explored for the purpose of benchmarking energy performances of schools. The results were used to understand the benefits of using these benchmarks for assessing energy efficiency of buildings and the limitations that affect the robustness of the derived benchmarks. Compared to the bottom-up approach, top-down approaches were found to be beneficial in gaining insight into how peers perform. The relative rather than absolute feedback on energy efficiency meant that peer pressure was a motivator for improvement. On the other hand, there were limitations with regard to the extent to which the energy efficiency of a building could be accurately assessed using the top-down benchmarks. Moreover, difficulties in acquiring adequate data were identified as a key limitation to using the top-down approach for benchmarking non-domestic buildings. The study suggested that there are benefits in rolling out of DECs to private sector buildings and that there is a need to explore more complex methods to provide more accurate indication of energy efficiency in non-domestic buildings

Realising operational energy performance in non-domestic buildings: Lessons learnt from initiatives applied in Cambridge

© 2017 by the authors. The gap between the intended and actual energy performance of buildings is increasingly well documented in the non-domestic building sector. Recognition of this issue has led to the availability of a large range of initiatives that seek to ensure energy efficient building operation. This article reviews the practical implementation of three such initiatives in a case study building at the University of Cambridge. The notionally high-performance office/laboratory building implemented two voluntary design frameworks during building planning and construction: the voluntary rating scheme BREEAM and a bespoke Soft Landings framework called the CambridgeWork Plan. The building additionally meets the energy reporting criteria for the EU Energy Performance of Buildings Directive (EPBD), a legislative requirement for many publicly owned buildings in the UK. The relative impact of these three approaches for optimising building energy performance is reviewed through a mixed methods approach of building occupant and operator interviews, document analysis and energy performance review. The building's core functions were revealed to consume 140% more energy than the building logbook estimate for the same needs. This difference, referred to widely as the energy performance gap, is larger than the majority of reported UK university buildings in the energy reporting database CarbonBuzz. The three implemented initiatives are demonstrated to be inadequate for reducing the energy performance gap in the case study, thus a number of alternative energy efficiency approaches are additionally reviewed. Common to the three approaches used in the case study is a lack of verification of actual building performance despite ambitious sustainability targets, due to a heavy focus on the design-stage and few follow-up mechanisms. The paper demonstrates the potential of energy efficiency initiatives that are focussed on operational performance as a core criterion (such as the Living Building Challenge) together with those that ensure the creation of realistic energy estimates at the design stage (such as the Chartered Institution of Building Services Engineers (CIBSE) Technical Memorandum 54)

Managing the risk of the energy performance gap in non-domestic buildings

Energy use in buildings accounts for one-third of the overall global energy consumption and total building floor area continues to increase each year as new developments are constructed and delivered. If stringent climate goals are to be met, these buildings will need to consume less energy and emit less carbon. However, design intentions for energy efficient buildings are not always met in practice. This performance gap between calculated and measured energy use in buildings threatens the progress necessary to meet these energy targets. The aim of this paper is to identify the factors that contribute to the performance gap and propose solutions for reducing the gap in practice. A quantitative and qualitative analysis of two research programmes completed in the past few years was utilized for an in-depth look at the performance of around 50 non-domestic buildings in the United Kingdom. While no direct links were found between any one variable and the performance gap, several correlations exist between contributing factors indicating a complex, entangled web of interrelated problems. The multitude of the variables involved presents a formidable challenge in finding practical solutions. However, the results indicate that the combination of the ventilation strategy of a building and the building services control strategy during partial occupancy is a key determinant of the performance gap. A more straightforward procurement approach with clearly delineated targets and responsibilities, along with advanced and seasonal commissioning instituted at the beginning of a project and implemented after building completion can also be very effective in reducing the gap. Finally, mandatory requirements or an appropriate system of incentives for monitoring and disclosure of performance data can help identify many of the underlying issues affecting performance in-use and untangle some of the web of complex issues across the building sector

A review of existing building benchmarks and the development of a set of reference office buildings for England and Wales

The modern built environment has become more complex in terms of building types, environmental systems and use profiles. This complexity causes difficulties in terms of optimising buildings energy design. In this circumstance, introducing a set of prototype reference buildings, or so called benchmark buildings, that are able to represent all or majority parts of the UK building stock may be useful for the examination of the impact of national energy policies on building energy consumption. This study proposes a set of reference office buildings for England and Wales based on the information collected from the Non-Domestic Building Stock (NDBS) project and an intensive review of the existing building benchmarks. The proposed building benchmark comprises 10 prototypical reference buildings, which in relation to built form and size, represent 95% of office buildings in England and Wales. This building benchmark provides a platform for those involved in building energy simulations to evaluate energy-efficiency measures and for policy-makers to assess the influence of different building energy policies

Improving Environmental Sustainability in Reuse of Some of England’s Churches: Challenges and Options for Sustainable Practices

Considering the spontaneous growth in retrofitting practices, existing buildings, particularly those of historical significance are being transformed using a wide range of interventions. However, the pervasiveness of these interventions constitutes a serious challenge to retrofitting heritage buildings. The aim of this paper is to investigate current retrofitting strategies and interventions in heritage buildings. The purpose is to assess current performance through the viewpoint of energy efficiency. The paper adopted pragmatic analytic and comparative approach and methodology to investigating retrofitting interventions in the reuse of England listed churches. A top down approach method of data collection was employed to collect energy use data from monthly utility bills and meter printer outs from selected buildings. Findings show that in terms of energy performance, the majority of the surveyed buildings are currently under-performing. Recommendations for low energy use interventions for operational management of retrofitting projects were proposed. It concluded that the low operational energy use should be a key priority for effectiveness in any proposed retrofitting intervention on heritage building projects

Assessing the trends of energy use of public non-domestic buildings in England and Wales

Accessing sufficient data for understanding how energy is used in non-domestic buildings is deemed to be a challenge in many countries. In the UK, such a challenge has led to limited understanding of long-term changes in energy use of buildings. This study aims to develop a deeper understanding of the trends in energy use across the public sector non-domestic buildings in England. Display energy certificate (DEC) data which relate to 59,740 public sector non-domestic buildings in England and Wales were analysed. Statistical analyses were carried out to understand both the latest patterns of energy use and how they have changed between 2010 and 2016. The patterns of energy use of various public-sector buildings were found to have gradually changed over the seven-year period. An imminent release of a revised dataset was deemed necessary for understanding the performance of buildings to support the aspirations set out in the clean growth strategy. The study pointed to a need for regularly gathering and sharing data for understanding the changes in the patterns of energy use of the stock. Developing a framework that can facilitate this would enable various stakeholders make informed decisions for improving energy efficiency of the UK’s non-domestic buildings. Practical application: Statistics on electrical and fossil-thermal energy use intensity provide up-to-date reference points for assessing operational energy efficiency of public sector buildings. Principles for developing a framework are provided to support various stakeholders make informed decisions on for example setting design targets or making capital investments

Bridging the gap between energy and comfort: Post-occupancy evaluation of two higher-education buildings in Sheffield

Recent technical guidance has suggested that comfort and energy efficiency should not be seen as mutually exclusive [CIBSE, “TM54: Evaluating operational energy performance of buildings at the design stage”, 2013]. Currently, however, there is a lack of comprehensive understanding of energy use during building operation and how it influences user comfort. Through comparison of the complex relationships between energy, thermal comfort, and environmental strategy in two flexible highereducation buildings in Sheffield, this paper demonstrates how designers can utilise aspects of active and passive design to deliver more comfortable, lower-energy workspaces. Analysis of the authors’ post-occupancy evaluation of each case study examines what lessons might be learnt and applied to other institutional buildings in order to save energy without compromising occupant comfort. The findings illustrate how perceptions of comfort can be improved by increasing the degree of environmental control occupants have without necessarily increasing energy consumption. The paper highlights the significance of occupancy patterns to a complete understanding of energy efficiency and comfort, and speculates that the prediction and assessment of energy per occupant may have an important future role to play in bridging the gap between energy performance and comfort

Building Schools for the Future: Lessons Learned From Performance Evaluations of Five Secondary Schools and Academies in England

Building performance evaluations (BPE) of five secondary schools and academies constructed under the Building Schools for the Future (BSF) programme in England found that CO2 emissions associated with operational energy performance in all these buildings is higher than the median of the secondary schools. Whilst the new regulatory requirements for building fabric performance have led to some improvements in heating energy when compared against good practice and typical benchmarks, there is still significant discrepancy between heating energy use and the design expectations. Electricity use in these buildings is also 37–191% more than the median school and significantly worse than the design expectations. These results point to the importance of post-occupancy building fine-tuning and measurement and verification of performance in-use with respect to design projections to narrow the performance gap. It is also necessary to set out clear operational performance targets and protect energy efficiency measures from value engineering throughout building procurement and in operation to achieve good level of performance. Finally, it is suggested to adopt a holistic view of energy, environmental quality, and educational performance to have a better understanding of schools' performance and potential conflicts between energy efficiency measures and indoor environmental quality (IEQ)