The thesis is organised in eight Chapters. Chapters Two and Three include an investigation of the key issues relevant to the current research i.e. daylighting concepts, introduction to the daylight design and performance of atrium buildings. They set the background and general context for the research area.
Chapters Four, Five, Six and Seven consist of the research methodology, analysis and interpretation/discussion of the results of the parametric studies of atrium facades from the physical scale model study and the RADIANCE simulations. Chapter Five includes a comparison of the DF and the ADF results from the different methodological approaches: physical scale model, RADIANCE and the ADF algorithm by Littlefair (2002).
The concluding Chapter Eight outlines key findings from the study and identifies important research areas for the future.
A more detailed presentation of the content of each Chapter is given in the following paragraphs.
Chapter Two starts with an introduction to the key daylighting concepts related to the study. The next section explains the Commission Internationale de l'Eclairage (CIE) Overcast sky which has been used for the experiments undertaken. Following this, an explanation of the DF and the ADF that have been primarily used to assess daylight levels in the atrium buildings for this study is provided. Finally, the Chapter focuses on fenestration to understand its impact on daylight performance of buildings.
Chapter Three provides background information on the research content: the atrium building and its daylight design. The chapter includes an introduction to the daylight linked atrium parameters and covers an extensive literature review of the prediction tools and of the key
The first part of Chapter Four highlights the importance of surfaces and their reflectances on how architecture and the spaces therein are perceived and experienced as elaborately described by Michel (1996). This is followed by detailed information related to the use of physical scale models in day-lighting studies. The final part includes the first parametric experiment which examines the effects of the different reflectance distributions and surface types (diffuse and specular) on the DFs on the atrium floor.
The aim of Chapter Five is to establish the accuracy of the different methods used to obtain the DFs and the ADFs on the atrium floor. To this end a comparative analysis between the physical model study and the RADIANCE simulation is undertaken. The ADF formula proposed by Littlefair (2002) is introduced and the ADF values obtained by the three different methods: physical scale model, algorithm and RADIANCE are also compared.
Chapter Six builds on the experiment undertaken in Chapter Four. It examines the effects of varying distributions of the atrium wall reflectances on the DFs and the ADFs in different atrium well Indices (WI 0.5, 1, and 2). This is undertaken to establish the range of well indices in which reflectance distributions affect the daylight levels. Where possible, data obtained from the RADIANCE models is compared with measured daylight performance data from real buildings available from Fontoynont’s (1999a) book.
Having established the range of well indices within which the atrium reflectance distributions affect the DFs and the ARCs in the previous Chapter, Chapter Seven parametrically assesses the effects of different fenestration distributions on the DFs in the atrium and its adjoining spaces. Atrium facade compositions with a progressive increase in openings from the top to the bottom floor as well as those with even openings on all of the floors except the ground floor (100% opening) are tested and compared. This is undertaken to explore whether particular fenestration ratios and an incremental approach to the fenestration from the atrium roof to its floor improves daylight conditions in the adjoining spaces of an atrium building. This is followed by an analysis and discussion of the results and comparisons with monitored data in real atrium buildings, where possible.
In the concluding Chapter Eight, the findings are summarised and specific conclusions with reference to atrium facade design to improve daylighting in atrium buildings under overcast sky conditions are drawn. Conclusions regarding the use of different daylighting assessment tools are drawn and observations on the daylighting strategies used in practice are also made. The Chapter concludes with an outline of the research contributions of this study and its limitations. Finally, the Chapter identifies research gaps and the opportunities for future research.
2 DAYLIGHT IN BUILDINGS: AN UNDERSTANDING OF THE
CONCEPTS
2.1 INTRODUCTION
This Chapter sets the scene for the ‘daylighting’ component of the thesis through an introduction to the key daylighting concepts and definitions including the direct and indirect sources of light; illuminance and luminance; and a detailed analysis of reflectance, absorptance and transmittance.
The second part of the Chapter describes the characteristics of the Commission Internationale de l'Eclairage (CIE) Overcast sky, and explains the concepts and definitions of Daylight Factor (DF) and Average Daylight Factor (ADF) including the methods of calculation that will be used in the subsequent Chapters.
Finally, the Chapter explores the behaviour of light as a result of fenestration in buildings through a focussed literature review; in particular it discusses the side and top lighting strategies and touches upon the glazing and roofing systems. The conclusion summarizes information related to daylighting in the context of the work which is subsequently undertaken in this thesis.