Conference PaperPDF Available

Office Buildings Daylighting Design in Hot Arid Regions: Forms, Codes and Occupants’ Point of View

Authors:
343
International Engineering Conference on Hot Arid Regions (IECHAR 2010)
Al-Ahsa, KSA, March 1-2, 2010
AbstractIn hot and arid regions, contemporary designers need
more daylighting related information in order to achieve an
environmental friendly and energy efficient architecture design.
This paper presents the results of a Post Occupancy Evaluation
research undertaken in an office building in the city of Biskra,
Algeria. This POE aims to fill this lack by providing practical
information. The field work took place during summer in the
building of La Caisse Nationale des Assurances Sociales (a major
state insurance company). Firstly, the study results presents the
different shape and photometric ratios revealed by the field survey
and discuss them according to the prevailing norms and design
guidelines recommended for buildings under clear sunny skies.
Secondly, it exposes the occupants‘ perception and behavior and
their relationships to the shapes, photometric values and relevant
standards for the hot arid context.
KeywordsArchitectural daylighting, hot arid regions, Luminous
ambience, office design.
1. INTRODUCTION
ot and arid regions are characterized by year round
clear sunny sky. Such potential should be an enormous
advantage in order to achieve an environmental friendly and
energy efficient architectural design. However, the situation
is another and this makes the hot arid regions presenting a
suitable context for daylighting investigations. In effect,
contemporary designers from these regions are against a
lack of present-day architectural references that let to an
adequate daylighting design avoiding overheating and glare
problems. Besides, the vernacular apertures aiming to admit
daylight and control sunlight are irrelevant when
considering the actual users‘ needs. In addition, the
academic research work leading with daylighting has been
and is always mainly focused on the overcast sky region
case. Moreover, it has been proved that the physical
standards for daylighting are culturally variable and couldn‘t
be considered as absolute daylighting design parameters in
any regional context.
Hence, a global approach is needed to encompass the
complexity of architectural daylighting design in hot arid
Manuscript received December 31, 2009.
A. Belakehal is with the Laboratoire de Conception et de Modélisation des
Formes et des Ambiances (LACOMOFA), Dept. of Architecture, M.
Khider University, 07000 Biskra , Algeria (phone : +213 772 944 222; fax:
+213 33 746 273; e-mail: belakehal@ gmail.com).
A. Bennadji is with the Scott Sutherland School for Architecture and the
Built Environment, Robert Gordon University, Aberdeen, AB10 7GD, UK
(e-mail: a.bennadji@rgu. ac.uk).
K. Tabet Aoul, Department of architecture, University of Science and
Technology, 31000 Oran, Algeria (e-mail: katabet@yahoo.fr).
regions. This approach should take into account the
quantitative parameters as well as the qualitative ones.
Whilst these latter are human related ones, the former is
dealing principally with physical aspects. For, this study
adopted the notion of ambience as a main theoretical frame
[1] - [2].
2. LUMINOUS AMBIENCE
Daylighting is defined as the practice of admitting natural
light into a building in a way which reduces the use of
electric lighting. Differently, the notion of luminous
ambience provides a new way to investigate the
relationships between natural light and architecture. In fact,
it introduces the human dimension within this association.
The research works on the ambience in the architectural
field go beyond the definition of this notion as a situation
associating people and the environment where they are
localized. They stress on the sensorial aspects emerging
from a certain physical stimulus that are taken for signals
(sound, light, smell…) whilst they were previously thought
as primary human needs [3]. Because this signal would be
insignificant if it is not perceived, a focus is made on the
users-receptors’ behavior. Architecture and the built
environment are indeed more seen as an inhabited place than
a visual form.
It has also been revealed that inside an architectural space
the ambiance is multiple that is to say it is not related to a
single signal. This makes characterizing the notion of
ambience as inescapably complex. Additionally, the context
has been attested as an influent parameter in the
characterization of an ambience. The context could act as: i)
a physical interior environment with specific formal and
spatial properties, ii) a physical exterior environment
creating particular stimuli, and/or iii) by means of users
dependently of their cultural, social and climatic context.
Researchers pay also a particular attention to the built
environment (urban as well as architectural spaces). A
formal characterization is used because the architectural
space remains the study object.
In a previous research work the development of a
conceptual model for the luminous ambience has been
carried out as an extension of what has been named a the
basic model for the notion of ambience[4]. This called
integrated model for the luminous ambience consists on
hypothetic relationships between [5]: i) the luminous
environment, ii) the architectural space, iii) the context, and
iv) the user. The components of this model are of very
different matters. Thus, they need an appropriate global
approach and a set of research techniques in order to
Office Buildings Daylighting Design in Hot Arid
Regions - Forms, Codes and Occupants‘ Point of
View
A. Belakehal, A. Bennadji and K. Aoul
H
344
overcome the emerging difficulties.
3. RESEARCH METHOD AND TECHNIQUES
In this study, the diagnostic level post-occupancy evaluation
method is presented as the most appropriate method to
globally approach a complex phenomenon like the luminous
ambience is [6]. Its suitability remains largely from: i) its
focalisation on the architectural space as perceived by its
users (an environmental psychological place centred
method), and ii) its ability to enclose several different
research techniques. Hence, four of these latter are selected
in order to collect the various needed data: i) the
questionnaire, ii) the behavioural map, iii) the architectural
survey, and iv) the photometric measurements. Because of
the complexity of these data and their different natures, the
analytical methods of their outcomes require a particular
attention. Statistical analysis linear methods for qualitative
data (multiple correspondences analysis) are those chosen
because most information is qualitative (nominal or ordinal).
The data resulting from the luminous environment indicators
(photometric characterization) basically quantitative are
converted to qualitative (ordinal) ones. This is a suitable
manner to associate them to the other collected data in order
to interpret them as a whole.
4. CASE STUDY
A field investigation took place in a contemporary office
building located in the urban setting of the city of Biskra. It
aims to apply the proposed occupant based conceptual
model of the luminous ambience. Offices present the kind of
buildings where good daylighting conditions are an
inescapable issue for the users‘ comfort. Biskra city is
located in the northern part of the Algerian Sahara which is
characterized by a semi arid hot climate and a clear sunny
sky almost year around. The office building houses a major
state insurance company (Caisse Nationale de l‘Assurance
Sociale). The building is five storeys high organized around
an uncovered courtyard and with four facades (Fig. 1). The
majority of offices are of a small size. Open plan offices are
few but exist in every floor.
Fig. 1 A view of the Caisse Nationale de l‘Assurance Sociale
Building
A questionnaire was administrated, face to face, to thirty
nine occupants (20% of the total number of occupants) in
twenty four offices (42% of the total number of offices).
Further, the occupants‘ behavior was observed, particularly
their reaction to daylight and sunlight. Along, a photometric
characterization of the luminous environment was done for
every questioned occupant. This characterization is made in
respect to an improved protocol of measurements developed
for this research work [7]. Also, an architectural survey was
made for every office concerned by the investigation.
5. OPENINGS MORPHOLOGICAL CHARACTERISTICS
The first results of the study concern the openings
morphological characteristics and include: i) the window
size, proportion and location, ii) the window area to the
façade wall area ratio, iii) the window area to room area
ratio, and iv) the window head height to room depth ratio.
These results are related to the offices occupied by the
interviewed workers. The morphological characteristics are
studied at the initial condition as the architect designed
them. That is to say, the various occultation introduced by
the workers, by means of movable solar protections, are not
taken into account at this level of the results presentation.
The openings size is of two kinds: i) small windows looking
as holes in the wall, and ii) larger openings with various
sizes. According to Baker et al classification [8], the shapes
of this second openings category vary from vertical to
intermediate. No horizontal openings exist in the CNAS
office building. The smallest openings have mostly a square
shaping. 41% of the interviewed occupants are working in
offices with an opening located at the middle of the façade
wall whilst 59% of them have their opening near the wall
corners.
The window area to the façade wall area ratio (WWR)
varies from 4% to 55% in the investigated offices. More
than a half (59%) of the interviewed occupants works in
offices where the WWR represents less than the quarter
(25%) of the façade wall. Nearly the quarter of them (23%)
are in offices with a WWR equal to 25%. A small number,
but not less significant, of occupants (15,4%) are in offices
with a WWR between the 25% and 50%. Very few workers
(2,6%) occupy offices with a WWR superior to 50%.
The window area to the room area ratio (WRR) varies
from a minimum of 7% to a maximum slightly superior to
60%. The third (33%) and more than a third (38,4%) of the
interviewed workers occupy offices where the WRR is
varying respectively from 20% to 30% and from 30% to
40%.
The window head height to the room depth ratio (WDR)
maximum and minimum values are respectively 1,03 and
4,60. Slightly more than the three quarters of the
interviewed employees are working in offices where the
WDR is under the value of 2 whilst for 15,4% of them the
WDR is between 2 and 3.
6. PHOTOMETRIC CHARACTERIZATION OF THE LUMINOUS
ENVIRONMENT
The second part of the research results focuses on the
luminous environment characterization by means of a set of
photometric measures. These latter are taken at the office
worker eyes level for both micro-visual field and macro-
visual field. The former is the field seen by the office
worker when achieving his task (looking at the task area).
345
The latter is the one viewed when he raises his head and
looks frontward. The illuminance value at the task level is
the measure used in order to characterize the micro-visual
field. The maximal luminance value is adopted for the
macro-visual field one.
The illuminance values measured at the task level for the
surveyed office workers vary from a minimum value of 18
lux to a maximum one of 1078 lux. For 30,5% and 46,1% of
the office workers the illuminance value is, respectively,
ranging from 100 lux to300 lux and from 300 lux to 500 lux.
A few of them are working under illuminance values
inferior than 100 lux (10%) or superior than 1000 lux (2,6%)
(Fig. 2).
Fig. 2 The measured horizontal illuminance values
The maximal luminance value received by an interviewed
occupant from his macro-visual field is 4995 cd/m2 whilst
the minimal one is 7 cd/m2 (Fig. 3). An important number of
the surveyed occupants (71,8%) receive luminance values
under 500 cd/m2. Few of them are in front of surfaces
reflecting luminance values of 500 cd/m2 to 1000 cd/m2
(7,7%) and 1500 cd/m2 to 2000 cd/m2 (10%).
Fig.3 An example of a picture showing the values of the
measured luminance in the macro-visual field
7. COMPARISON WITH CODES AND DESIGN GUIDELINES
Building design standards could be performing
established by ergonomics and building physicians such as
illuminance and luminance ratio values. They could be also
prescriptive preferred by architects and known by rules of
thumbs. However, the Algerian building regulation did not
include any daylighting standards for public buildings.
Because of the lack of such information, it was decided that
the results of the study will be discussed in comparison with
current academic daylighting design guidelines. A more
attention is paid to those specific to hot arid /clear sunny sky
regions.
The result of a previous research work on window size in
hot and arid climate reveals the influence of window shape
and size on sunlight penetration [9]. It attests that vertical
windows are efficient only for the south-east and south-west
oriented facades. For a similar wall depth (36 cm), it is
recommended the use of windows with a width inferior to
75 cm. From the daylighting point of view, another study
focusing on daylighting design in buildings under a clear
sky shows that the variation of the window shape from
extreme vertical to extreme horizontal did not affect
significantly the illuminance values at the horizontal level
particularly at more than 2m from the window [10].
However, it is the window area which contributes strongly
to the variation of the illuminance levels at the deepest
zones of a room. In addition, the vertical narrow opening
located at the walls corners is very suitable in regions when
clear sunny sky prevails. This should allow a better
protection against glare effects [11]. In respect to these
findings and to the orientation of the studied building
facades, it will be clear that the large vertical windows
create some sun penetration problems. These latter should in
turn affect the luminous ambience inside the offices.
Moreover, their location within the façade wall is not
effective for the glare protection.
For Biskra city, the Mahoney tables give a WWR varying
from 15% to 25% [12]. This ratio is respected in the offices
occupied by 82,1% by the interviewed workers. Three
values are recommended for the WGR: i) from 10% to 12%
[13], ii) 8% to reduce to 6% for the case of extreme desert
regions [14], and iii) a minimum of 6% [15]. Only one,
among all the investigated offices, has a WGR which is
respectful of the recommended ratio for similar climatic
regions. Recently, the efficient daylighted zone has been
extended from 1,5 to 2 for the case of a sidelighting room
[16]. According to this value, the window head height to the
room depth ratio of the studied offices shows that 75% of
their occupants are working within the efficient daylighted
zone.
The recommended illuminance values for the micro-
visual field (at the task level) in an office are between 200
lux and 600 lux [17]. For the case of the macro-visual field,
Baker et al [8] assert that a luminance value superior to 500
cd/m2 has to be considered as glaring when the room is
daylighted. The same value is confirmed by a different
author for the case of the luminance reflected from a big size
zone like a window or a wall [18]. In addition, he specified
that for the luminance of sky perceived through the window
a value of 2000 cd/m2 is inconvenient. The measured values
at the work stations reveal that those exceeding 2000 cd/m2
represent only 7,8% of them. Also, they show that among
39 analyzed macro-visual fields, only two includes values
superior to 500 cd/m2.
8. THE OCCUPANTS POINT OF VIEW
The interviewed occupants have been asked about the
luminous environment of their offices. The windows
y = 39 * 1 00 * n orma l (x, 3 41.43 6, 20 9.847 )
Ecl airem ent l umi neux horiz ontal mersuré (lux)
Nombre d'Obs
10.3%
20.5%
10.3%
28.2%
17.9%
5.1% 5.1%
2.6%
0
1
2
3
4
5
6
7
8
9
10
11
12
<= 0 (0,100]
(100,200]
(200,300]
(300,400]
(400,500]
(500,600]
(600,700]
(700,800]
(800,900]
(900,1000]
(1000,1100]
> 11 00
346
occultation by means of movable solar protections (curtains)
has been also analyzed which led to new ratios.
About the luminous environment on their desks (micro-
visual field), a pilot study reveals that the suitable question
form within concern to this matter should be related to their
eyes fatigue where they are performing their tasks. Slightly
above the third of the interviewed occupants (35%) said that
it was not fatiguing at all, 20,5% not fatiguing, 10,3%
neutral, 20,5% somewhat fatiguing and 12,8% too fatiguing.
The luminous environment at the macro-visual field is
qualified by 74,4% of the interviewed occupants as suitable,
23,1% as too clear and only 2,6% as too dark. The zone
where are located the desks is described as a clear one by
most of the occupants (94,4%) whilst solely a few of them
perceived it as gloomy (5,1%). The statistical data analysis
does not reveal any significant relationships between the
measured values and the occupants‘ answers as it is usual in
experimental research work settings. This may be due to the
fact that a field studies emphasizes more variables than the
experimental ones and a linear relationship should not be
easy to carry out.
The pilot study shows that the office workers adjust the
heavy curtains in function of the time of the day. Thus, a
survey of this action has been done at the same time of the
photometric measuring (Fig. 4).
Fig. 4 A view of an office showing the effect of the use (above)
or not (down) of the curtains on the luminous environment
The results of the survey are presented in the form of
two values: i) the occultation percentage and ii) the WRR
after occultation of the window. The first value represents
the area of the occulted area of the window as a percentage
of the whole (initial) window area. Slightly above the quart
(28,2%) of the occupants occult less than 20% of their
window whilst 23,1 %, 20,5%, 15,4% and 12,8% occult
respectively 20% to 40%, 40% to 60%, 60% to 80% and
above to 80%. The WRR for an important number of the
office workers (74,6%) became not exceeding 25% (Fig. 5)
whilst this ratio value (from 20% to 30%) exists for the
offices where work only 38,4% occupants.
Fig. 5 The various categories (in percentage of the interviewed
users) of the occulted window area to the room area ratio (WRR)
9. CONCLUSION
Whilst daylighting is more and more perceived and
proved to be an efficient strategy for a sustainable design,
the hot arid regions seems to not being ready to take
advantage of the great benefit it posses that is daylight. This
research work shows that Algeria as a country form this area
of the world has not any building regulation or any
recommendation related to daylight for public buildings.
This study tries to look at this topic by means of a theory
and an approach involving the users‘ perceptions and
behaviors.
The results reveal that the building design was not
respectful of the daylight related guidelines for building in
the hot arid regions. This could inform about the knowledge
of the architects about daylighting design which in turn
invites to explore this area within the architectural practice
and training. This became particularly more and more
pressing at the time when sustainable design is one of the
keys to preserve earth life.
The study outcomes show also that the users adapt their
luminous to their needs and their comfort levels by simple
means such as curtains. However they did not give precise
relationships in order to fond performing and/or prescriptive
daylighting design related building codes. For, it could be
suggested undertaking more experimental research in this
topic for the case of building under a clear sunny sky.
REFERENCES
[1] P. Amphoux (Ed.) La Notion d‘Ambiance. Une Mutation de la Pensée
Urbaine et de la Pratique Architecturale. Paris : Plan Urbanisme,
Construction, Architecture, 1998.
Rapport surface fenêtre occultée / surface au sol
<= .121, 30.8 %
> .483, 2.6 %
(.241,.362], 23.1 %
(.121,.241], 43.6 %
347
[2] J-F. Augoyard, ―Eléments pour une théorie des ambiances
architecturales et urbaines,‖ Les Cahiers de la Recherche
Architecturale, n° 42/43, pp.13-23, 3rd trimester. 1998.
[3] G. Broadbent, Design in Architecture. Architecture and Human
Sciences. Great Britain : David Fulton Publishers Ltd., 1988.
[4] Belakehal, ―Etude des Aspects Qualitatifs de l‘Eclairage Naturel dans
les Espaces Architecturaux. Cas des milieux Arides à Climat Chaud et
Sec, Doctorate Degree Thesis, Dept. Architecture, M. Khider
University, Biskra, Algeria, 2007.
[5] Belakehal et al, ―Towards an occupant based conceptual model. Case
of the natural luminous ambience,‖ in Proc. 2009 PLEA Conference,
Quebec City, 2009, (10pages).
[6] J. C. Vischer, Environmental Quality in Offices. New York: Van
Nostrand Reinhold, 1989.
A. Belakehal et al, An evaluation method for daylighting quality in
buildings under clear sunny skies,‖ In Proc. 3rd EPUK Conference,
Aberdeen, 2003, pp.70-79.
[7] N. Baker et al, Daylighting in Architecture. A European Reference
Book. London: James and James, 1993.
[8] M. Al-Jawadi and A. J. T. Al-Noah, ―The best window proportions in
housing design fro latitude 33° N,‖ In Proc. International Conference
on Housing, Miami, Vol. 2, pp. 753-758, 1979.
[9] M. S. Millet et al, ―Graphic daylighting design method: including clear
sky conditions,‖ In Proc. National passive Solar Conference, Boulder,
pp.1183-1191, 1980.
[10] Konya, Design Primer for Hot Climates. London: The Architectural
Press Ltd, 1980.
[11] K. Tabet Aoul, Bioclimatic potentialities of contemporary housing
estates. Architecture, energy and comfort in Algeria. Lund Centre for
Habitat Studies, Lund University, (10 pages), 1999. Available :
www.hdm.lth.se/aee/paper/ 1999/01_AEE1999.pdf
[12] M. Evans, Housing, Climate and Comfort. London: The Architectural
Press Ltd, 1980.
[13] S. Saini, Building in Hot Dry Climates. New York: John Wiley and
Sons, 1980.
[14] Y. Etzion, Openings in hot climates wind, sun and shading,‖. In
Proc. International Workshop on Climatically Responsive Energy
Efficient Architceture, Delhi, pp.1-21, 1995.
[15] N. Baker and K. Steemers, Daylight Design of Buildings. London:
James and James, 2002.
[16] M. Fontoynont (Ed.), Daylight Performance of Buildings. London:
James and James, 1999.
[17] V. Berruto, Métrologie de la Qualité Visuelle des Ambiances
Lumineuses. Application à l‘Eclairage des Bureaux. Doctorate Degree
Thesis,, University of Savoie, France, 1996.
Azeddine BELAKEHAL studied architecture at the Biskra University in
Algeria. He graduated in 1991 and continued to work as an architect-
principal in a technical public office. In 1996, he gained his Masters
Degree, specialising in ‗Architecture within Arid Regions‘, presented his
Doctorate Degree in 2007: The Qualitative Aspects of Architectural
Daylighting Design while being employed as an assistant-professor at the
Department of Architecture at Biskra University, Algeria. In October 2009,
Azeddine receive the diploma of ability for supervising reseqrch works
from the University of Biskra. BELAKEHAL has consulted on a number of
urban planning project studies carried out by governmental agencies for
new human settlements in the Algerian desert. He has a particular passion
for environmental design issues pertaining to architecture and has been
commissioned for several research projects by national and international
organizations. Azeddine has served as Jury member on several projects and
has been widely published in a number of well known architecture and
research journals as well as participated in several national scientific events
and international specialized conferences and congress.
Kheira A. Tabet-Aoul (PhD, LEED AP) graduated as an architect (1986)
from the school of Architecture, University and Science and Technology of
Oran (Algeria). In 1991 a PhD was completed in Building Science from the
School of Architecture, Sheffield University (UK). She is a LEED (
Leadership in Environmental Design)Accredited Professional (2008) and
Green Advantage Certified for Commercial practitioners (2008).
Sustainability in the built environment is the area of expertise. She is
presently a senior consultant on sustainability (Nevada, USA). She has
taught architecture and sustainability for over 15 years as well as
supervised Master and PhD's. She has over 50 papers published in refereed
International, National Journals and Proceedings of Conferences.
Daylighting, sustainability in arid zones and the human performance in
sustainable environments have been the main areas of research. Pr Tabet-
Aoul is a member of the US Green Building Council and the Nevada
Chapter (US), The Scientific and Technical Research Center on Arid Zones
(Algeria); The Center of Renewable Energies Development (Algeria); and
the Fullbright Association (US) since receiving the J. William Fullbright
Award.
He started his professional experience at the French ministry of finance
in 1992 while doing his PhD, he moved then to Loughborough University
for a post doctoral position, where he worked on the development of
software for energy saving in collaboration with ARUP and Amec the two
construction leading companies in the UK. He is currently based in
Scotland lecturing at Robert Gordon University in Aberdeen. He is also a
member of the Innovation, DEsign And Sustainability Research Institute
(IDEAS).
His research interest goes to the Energy Conservation in buildings with an
emphasis on existing building as part of retrofitting approach where he
believe we still have a lot to offer in this field as part of sustainable
approach. As a leader for an MSc course in "property Development" he
included the sustainability component in the course to make sure
developers includes it in their development equation.
He published several papers and his PhD thesis was published as a book
twice to reach a wider audience.
ResearchGate has not been able to resolve any citations for this publication.
Conference Paper
Full-text available
Dealing with thoughts based on the ambience notion, the present research work makes for a contribution consisting on the development of an occupant based model for the natural luminous ambience. One of the ambience notion virtues is the supply of the architectural research with specific to architecture theoretical bases whilst preserving its links to other fields with an environmental spirit. This notion provides new components for the study of the environmental physical stimuli within the built spaces that is the requirement of the plurisensoriality. Hence, the proposed conceptual model will be beyond the conventional ones because it associates the context particularities, the luminous environment and the architectural space to the user. An office building from an east- southern Algerian city under a clear sunny has been chosen as a case study to apply this conceptual model. The field research work proves the feasibility of the model and indicates the hierarchy of the hypothesized relationships but also reveals the unsuitability of some statistical analysis methods.
Book
Full-text available
This book is a guide to the conservation and control of energy use in buildings for national energy planners and researchers, architects, engineers, building owners, and managers. Historical information on energy use in buildings and a new framework for classifying the roles and concerns of all groups involved in building energy performance are presented. It also permits access to detailed information for those with particular interests: strategies and techniques of energy management, successful conservation programs, energy prediction methods and factors affecting energy consumption, and the underlying principles of building energy performance standards. Results of field surveys on large numbers of commercial and institutional buildings, indexes of building energy performance and relevant data, and Sl and l-P units supplement this guide. CONTENTS: Energy and Building -- Evolving Concerns. Building Energy Performance -- A New Framework. National Concerns -Institutional Roles and Energy Standards. Owner Concerns. Designer Concerns -- Capital Energy Requirements. Designer Concerns -- Systems Energy Consumption. User Concerns -- Energy Management and Analysis. Building Energy Performance -- Future Concerns. Index.
Article
Useful, cost-effective, and encouraging information about building in industrially impoverished parts of the world is presented. Specific examples of projects, and many simple illustrations, and photographs are included.
Conference Paper
The Graphic Daylighting Design Method (GDDM) developed by Millet and Bedrick for overcast sky conditions is being extended to include a clear sky daylighting prediction capability, which will allow the method to be used in conjunction with passive solar design techniques. The core of the method for each of the two design conditions is a set of patterns, or footprints, which portray illumination distribution over the workplane for a variety of window configurations. Like the overcast sky design method, this clear sky method is useful for the designer at the schematic design stage, because it allows rapid evaluation of many different window configurations at a time before the building design is finalized. Both the clear and overcast design methods are useful aids for the teaching of daylighting, because they incorporate visual representations of what is occurring in a room in terms of level of illumination, distribution of light on the workplane, and movement of light across the workplane throughout the day. The effects of clear sky variables on light quantities and light distribution on the workplane are described, and the development and use of the clear sky footprint are explained.