The Impacts of Contributory Factors in the Gap between Predicted and Actual Office Building Energy Use

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Ten years ago, the primary author developed the Building Energy-Efficient Hive (BEEHive) concept in order to demonstrate in theory that environmental design – which is aimed at addressing environmental parameters – can support the design and operation of energy-efficient office buildings. This was a result of his analysis of the spheroid form’s efficiency in nature, and his development of a spheroid-like energy-efficient office built form that encloses and shades the most volume of office space with the least surface area possible. The BEEHive concept also incorporates several other aspects of the environmental design philosophy, including: site considerations (location and weather, microclimate, site layout and orientation); built form (shape, thermal response, insulation and windows/glazing); ventilation strategy; daylighting strategy; and services strategy (plants and controls, fuels and metering). Furthermore, several notable environmental design advocates and practitioners have made significant contributions in order to improve building performance. However, in practice environmental design has had limited success in the attainment of balance and optimisation in all aspects of energy use; hence there is typically a gap between predicted and actual office building energy use. This study has established the impacts of contributory factors in the gap between predicted and actual office building energy use, and it is a part of the primary author’s doctor of philosophy (Ph.D) research. It involved a combination of literature reviews, multiple case study research and comparative studies in order to build theory, and it established the reasons for the gap, as well as the best ways to bridge it for improved office building environmental design and energy performance. Analysis of the literature revealed two types of gaps, and these are a gap increase and a gap decrease, which are among the impacts attributable to contributory factors in the gap between predicted and actual office building energy use such as: the nature of environmental design measures implemented; weather variation and microclimates; unavailability of reliable building energy use data; limitations of building energy simulation software; level of hours of operation; and level and nature of occupancy. Amongst these, the key contributors to gap increases are increases in hours of operation and occupancy, and weather variation and microclimates. Their respective major impacts are discrepancy between predicted and actual hours of operation and increased energy use, increased heat output and uncertainties, and variable heating and cooling requirements. The key contributors to gap decreases are environmental design measures such as the use of: natural ventilation strategies; daylighting strategies; solar photovoltaic systems; and spheroid-like built forms. Their respective major impacts are: the production of more energy than an office building uses; and energy uses that are below, for instance, Energy Consumption Guide 19 typical and good practice energy use for office type 4, and relevant ASHRAE (American Society of Heating, Refrigerating and Air Conditioning Engineers) standards. This study has contributed to ideas for the development of a Building Management System for Bridging the Gap, otherwise known as ‘BMS-Optimum’, which is comprised of optimum conditions and considerations such as: optimum environmental design principles; optimum weather and microclimate considerations; accessibility to reliable office building energy use data; optimum building energy and environmental assessment; optimum hours of operation; and optimum level and nature of occupancy. Future work will include further development of BMS-Optimum, using methods such as: multiple case study research supported by building energy use audits, observations, questionnaire surveys, interviews, benchmarking and comparative studies; building energy simulations within multiple scenarios, parameters and variables, and supported by benchmarking and comparative studies; and peer reviews and focus group sessions. These will also help establish and validate a Framework for Improved Environmental Design and Energy Performance (FEDEP).