LESSONS LEARNED from the BEDZED DEVELOPMENT Janet
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TOWARDS ZERO ENERGY BUILDINGS: LESSONS LEARNED FROM THE BEDZED DEVELOPMENT Janet Young The Bartlett School of Graduate Studies University College London A thesis submitted for the degree of Doctor of Philosophy University College London September 2015 1 Declaration I, Janet YOUNG, confirm that the work presented in this thesis is my own. Where information has been derived from other sources, I confirm that this has been indicated in the thesis. 2 Abstract In order for the UK to meet carbon reduction targets and increased demand for housing from a growing population, houses need to be built that use less energy. Designers have responded by designing low energy buildings but little research has been undertaken on the actual performance of such buildings in use. This study compares the performance in use of 24 dwellings at the Beddington Zero Energy Development (BedZED) designed as a zero energy development. A unique feature is that, for the first time in energy monitoring studies, measurement of dwelling performance in use was undertaken both in the newly built dwellings and dwellings occupied previously by the study's participants. The results show that the dwellings achieved their design temperature during the heating season and that occupants were generally satisfied with winter comfort levels. Energy usage was lower in the new properties than previous dwellings and lower than comparable new dwellings at the time, broadly achieving the Passivhaus standard. The dwellings achieved a good standard of airtightness although there were some reports of condensation. Internal temperatures in the summer months showed a potential to overheat during hot spells and occupants were less satisfied with summer comfort. It is considered that this was partly because occupants were not familiar with how to cool their homes. The study reviewed Energy Performance Certificates issued for BedZED properties sold/rented and found them to be inconsistent and inaccurate. This has implications for the marketability of future low energy homes if not addressed by industry. It also found inconsistency in the application of measurement systems in the various models used. 3 Acknowledgements There are many people and organisations that have helped me complete the research and writing of this thesis. I am particularly grateful to my supervisor at UCL, Tadj Oreszczyn, who has supported and guided me through this long endeavour. Also to Alex Summerfield who assisted with the classification and organisation of my data and Payel Das who advised on statistical analysis techniques. I am grateful to Sung Hong and Dejan Mumovic for completing an on-site survey on one of the case study properties. There are also many people who had the vision for the original BedZED development and helped build it. In particular, these include Dickon Robinson, Development Director at Peabody Trust, Pooran Desai and Nicole Lazarus of Bioregional, architect Bill Dunster and energy engineer Chris Twinn. Nic Wedlake and Tessa Barraclough of Peabody provided information about BedZED’s energy use and gave their time to explain it. I am grateful to Ian Orme and Sarah Gubbins of Rickaby Thompson Associates who installed data loggers, downloaded monitoring data for two phases of the study and conducted the occupancy surveys. The residents of BedZED, who agreed to participate in this study, gave access to their homes for a long period and also provided useful insights which assisted with the interpretation of data. Elaine Cloutman-Green provided the necessary drive and motivation to encourage me to finish writing when I was close to giving up. Most of all, I am grateful to David Harbud who has stoically supported me through the many years it has taken to complete this thesis and without whom I would never have finished. 4 Table of Contents Chapter 1 Introduction ................................................................................. 18 1.1 Research Context ............................................................................. 18 1.2 Research Aim, Hypothesis and Research Questions ........................ 19 1.3 Research Significance ...................................................................... 20 1.4 Thesis Structure ................................................................................ 21 Chapter 2 Literature Review ........................................................................ 25 2.1 Introduction ....................................................................................... 25 2.2 Scientific context ............................................................................... 26 2.3 Policy context .................................................................................... 27 2.4 Demand for Energy ........................................................................... 28 2.5 Building Regulations ......................................................................... 35 2.6 Modelling and Measurement systems ............................................... 36 2.7 Human Factors.................................................................................. 43 2.8 Passive Design, Low Energy and Zero Energy houses .................... 54 2.9 Passivhaus ........................................................................................ 57 2.10 Performance Gap .............................................................................. 61 2.11 BedZED in the literature .................................................................... 62 2.12 Conclusions ...................................................................................... 62 Chapter 3 Comparative Low Energy Case Studies ...................................... 64 3.1 Introduction ....................................................................................... 64 3.2 Pennyland ......................................................................................... 65 3.3 Linford ............................................................................................... 67 3.4 Milton Keynes Energy Park ............................................................... 68 3.5 Brixton Super-Insulated Houses ........................................................ 70 3.6 Retrofit Studies : York Energy Demonstration Project and the Warm Front Programme .............................................................................. 71 3.7 Carbon Reduction in Buildings (CaRB) ............................................. 72 3.8 Comparative Case Studies Conclusions ........................................... 73 Chapter 4 BedZED Case Study ................................................................... 74 4.1 Introduction ....................................................................................... 74 4.2 BedZED Development Team ............................................................ 74 4.3 BedZED Timelines ............................................................................ 75 4.4 BedZED Location .............................................................................. 75 5 4.5 BedZED Scheme .............................................................................. 77 4.6 BedZED Design Aims ....................................................................... 77 4.7 Land Use ........................................................................................... 77 4.8 Passive Design Principles ................................................................. 78 4.9 Building Physics ................................................................................ 85 4.10 Zero Energy ...................................................................................... 86 4.11 BedZED Energy Strategy .................................................................. 87 4.12 BedZED SAP Calculation .................................................................. 89 4.13 Designed Energy Usage ................................................................... 90 4.14 Whole Life Energy Use ..................................................................... 93 4.15 Mechanical and Electrical Systems ................................................... 94 4.16 CHP Design ...................................................................................... 97 4.17 Sizing the CHP plant ......................................................................... 99 4.18 Daylighting Design .......................................................................... 102 4.19 Ventilation Design ........................................................................... 103 4.20 Heating Design................................................................................ 105 4.21 Other BedZED studies .................................................................... 108 4.22 Before BedZED ............................................................................... 110 4.23 Case Study Conclusions ................................................................. 112 Chapter 5 Summer Overheating ................................................................ 114 5.1 Introduction ..................................................................................... 114 5.2 Weather Trends .............................................................................. 114 5.3 Definition of Hot Spells .................................................................... 115 5.4 Summer Comfort ............................................................................. 115 5.5 Impact of Hot Spells on Health .......................................................