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Assessing the operational performance of educational buildings against design expectations - a case study approach

Burman, E; (2016) Assessing the operational performance of educational buildings against design expectations - a case study approach. Doctoral thesis , UCL (University College London). Green open access

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Abstract

Overwhelming evidence shows the average global temperature is rising and climate change is happening. The severity of the potential consequences and the significance of early action to limit environmental damage have led to urgent calls for a concerted action from governments across the globe to adopt appropriate policies for climate change mitigation and adaptation. Energy consumption of buildings accounts for around 40% of total final energy use of the EU Member States and contributes to the anthropogenic CO₂ emissions that cause climate change. Therefore, improving energy efficiency of new and existing building stock is an indispensable component of climate change policy in the EU. The urge for reducing energy consumption is also driven by other factors such as energy security and fuel poverty. The European Union has set out an ambitious target for 2050 to reduce its Greenhouse Gas (GHG) emissions by 80-95% below 1990 levels. There are also interim targets for 2020 for 20% cut in GHG emissions from 1990 levels, and 20% improvement in energy efficiency over 1990 levels. The Energy Performance of Buildings Directive (EPBD) and its recast underpin most of the energy regulations implemented in the EU Member States to improve energy efficiency of the existing and new buildings. However, there are concerns about the effectiveness of the existing regulatory frameworks in achieving the energy saving targets set out both at the European and national levels. Building performance evaluations carried out on new buildings and major refurbishments often point to shortcomings in building procurement and failure to achieve the design targets. This shortfall in operational performance is called the performance gap. The performance gap may point to shortcomings in various performance metrics, but is often expressed as a shortfall in energy performance or carbon dioxide emissions associated with building energy use. To gain a better understanding of the nature of the performance gap and its root causes, this Engineering Doctorate programme adopted a case study approach to assess the operational performance of five educational buildings, constructed under the Building Schools for the Future (BSF) programme in England, against design expectations. It is suggested that educational buildings, broadly speaking, have similar activity and objective systems and therefore are suitable for comparative analysis. The building performance evaluation framework used for the case studies entails detailed review of operational energy performance against the industry benchmarks and energy performance calculations performed at design stages. Those aspects of the indoor environmental quality that are directly related to energy performance were also monitored and assessed to ensure energy efficiency measures do not compromise occupants’ comfort and well-being. These measurements were complemented by Building Use Studies to seek the feedback of schools’ staff about building performance and obtain a holistic view of performance in-use. Finally, a forensic review of design and as-built documentations along with the feedback received from building designers and contractors were used to identify the root causes for performance issues uncovered in the case studies. The findings show a marked reduction in fossil-thermal fuel use of most new-build schools against the benchmarks derived from the existing building stock thanks to improvements in building fabric and air tightness standards. However, electricity use of all case studies was significantly higher than benchmarks. Although ever-increasing use of ICT equipment in modern educational buildings can partly explain this surge in electricity use, significant improvement opportunities were identified for the control of building services. It was revealed that around half the electricity used in these buildings was consumed outside the core occupancy hours. The fossil-thermal fuel use of schools can also be further improved by using the existing zoning arrangements for heating systems to isolate the unoccupied spaces during out-of-hours and half-term operation. Assessment of the indoor environmental quality and building users’ feedback points to conflicts between various environmental strategies related to thermal comfort, ventilation, acoustics, and energy performance. These conflicts must be addressed to achieve the right balance between comfort and energy efficiency. Teachers expressed concerns about the effectiveness of open-plan learning resources specified for new schools. In addition to the pedagogical issues that may occur if teachers are not engaged in spatial planning of teaching spaces, the increasing tendency to open-plan design brings challenges for energy efficiency and building control that are not fully acknowledged during design and in operation. The outcomes of the regulatory energy performance calculations that are often used in the discourse about the performance gap cannot be directly used as yardsticks for performance in-use. This type of performance gap is called ‘the regulatory performance gap’ in this dissertation. It is demonstrated that, when these outcomes are adjusted to allow for equipment and miscellaneous non-regulated loads and are subject to the same carbon emission conversion factors used for operational ratings, they are close to the 10th or 25th percentile of the national building stock and can be used as good practice benchmarks for building performance that take into account key building characteristics such as shape, fabric and building services’ specification. However, these adjusted calculations cannot be used as baselines for energy performance as they are carried out under standardised operating conditions that do not necessarily represent real operation. It is recommended to move towards assessment of expected performance in-use following protocols such as CIBSE TM54 or ASHRAE 90.1 to have a better understanding of the extent of the performance gap. The performance gap determined by comparing the measured performance with the expected performance, often projected at design stages, is called ‘the static performance gap’ in this dissertation. While it is often more reliable than the regulatory performance gap, it is rooted in a static notion of building performance and does not take into account the longitudinal changes in building context. The performance gap that quantifies the effect of shortcomings in building design, construction and operation could be determined when the calculated and measured performance both represent actual operating conditions. This is called ‘the dynamic performance gap’ in this dissertation. The word ‘dynamic’ in this context means the computer model initially used to project building performance is updated to reflect the changes in building context. An appropriate measurement and verification framework is required to account for differences between modelled and actual operating conditions post-occupancy and separate the effect of human behaviour from technical issues that must be addressed to optimise operational performance. It is demonstrated how such a measurement and verification framework can work under the existing building regulations to define the energy performance gap with precision. This can help identify and address the performance gap in early stages of post-occupancy. The policy implications of this framework are explored. It is suggested that this framework can also facilitate the effective implementation of energy performance contracting which is supported by the new EU Directives, such as the Energy Efficiency Directive, and is a key step in narrowing the performance gap in new and existing buildings. Finally, this dissertation calls for measurement, verification and disclosure of performance data in the school estate, and more widely the public sector, to achieve better value for money. This may in turn also drive disclosure of performance data and further improvements in the private sector.

Type: Thesis (Doctoral)
Title: Assessing the operational performance of educational buildings against design expectations - a case study approach
Event: UCL (University College London)
Open access status: An open access version is available from UCL Discovery
Language: English
Keywords: Schools, Building Performance Evaluation, Energy Performance Gap, Indoor Environmental Quality, Building Use Studies, Measurement and Verification
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of the Built Environment
URI: http://discovery.ucl.ac.uk/id/eprint/1482161
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