A
BSTRACT
Daylight in the tropics is voluminous and offers a good
potential for illumination in building interior. This paper
investigates daylighting, through a square roof-aperture,
in an adjoining space of an atrium building. A series of
physical experiments using a 1:25 scale model of ten-
storey atrium building was conducted to measure the
interior daylight illuminance and its distribution in the
model under real tropical skies. A software based its
daylight calculation on ray-tracing method for beam light
transmission and flux transfer method for diffuse light
transmission was run to compare its calculations with the
measurements. The software was also run to evaluate the
daylighting performance of the atrium model. The results
show that light well configuration, space depth from the
well, and the sun position influence highly on interior
daylight in atrium space in tropical climate. A correlation
between the daylight penetration depth from the light
well edge was also presented as a function of the well
index.
Keywords
:
Daylighting, Atrium, Illuminance, Well index,
Tropics
I
NTRODUCTION
Atrium is a large open space with multiple stories high
and glazed roof over the top. It is an architectural design
aiming to introduce natural daylight from the glazed roof
for interior illumination (Toplighting). Atrium does not
only conserve electricity from lighting but also provide a
better interior environment.
Daylighting in atrium building has been investigated
extensively in high latitude regions. Liu et al. conducted
experiments to measure the daylight level in atrium’s
adjoining space using a scale model. Daylight factor
(DF), expressed mathematically as a ratio of the interior
daylight level (E
i
) to its corresponding exterior global
daylight illuminance (E
vg
), was used as the index to
describe the daylight level and its distribution in the
atrium.
E
i
DF =
E
vg
(1)
On this work, geometry of the light well was expressed
in term of well index (WI) that can be expressed as in Eq.
(2):
Corresponding Author:
H×(W + L)
WI =
2×W×L
, (2)
where H is height of the light well. W and L are width
and length of the light well, respectively. This index
relates vertical surface to horizontal surface areas of the
light well. The smaller is the value of WI, then the
shallower is the atrium building. High WI value thus
refers to a tall atrium building. A relationship between
the daylight distribution and atrium’s geometric shape
index was finally developed [1].
Szerman developed a monogram for a calculation of
the mean value of DF in an adjoining space [2]. The
calculation requires the fundamental design parameters
i.e. space position, atrium width, section-to-aspect ratio
SAR (height/depth), atrium wall and floor reflectance and
glazing type.
Kim and Boyer proposed also a relationship between
the shape of the atrium and DF at the center of an open
atrium [3]. The result illustrated that the vertical daylight
levels on the well wall and the room properties (size and
surface reflectances) contribute an important effect on the
daylight level in the adjoining space.
A study of Aizlewood demonstrated that the well
geometries and surface reflectances are very important
parameters which have a direct effect on the vertical
daylight levels at the atrium wall [4].
All the works mentioned above conducted experiments
to measure daylight illuminance and distribution using
scale model and artificial sky simulator. Another group
of the works made use of computer simulation to predict
daylight distribution in atrium building. This method
could give a more rapid evaluation of the design choices
[5], saving time and budget provided that the software is
supported by validation studies. Radiance [6] is a light
simulation software has been in widespread use in the
research. The software could give calculation results that
agree well with the measurements from experiments, thus
confirming its scientific validity [7-9]. Radiance has
become the most popular package for daylight modeling
in the built environment.
Sharples [10] and Du [11] indicated that many of the
researches investigating daylight in atria have tended to
focus upon illuminance levels on the atrium well floor.
This paper aims to present results of a study of
daylighting in atrium building in Thailand. The study
was made to be different from above studies by
conducting the scale model experiment outdoor under
real tropical sky. A computer software using ray-tracing
An experimental and simulation study of daylighting in
atrium building in the tropics
Siwaporn Meka
1
, Pipat Chaiwiwatworakul
1
, and Surapong Chirarattananon
1
1
The Joint Graduate School of Energy and Environment, King Mongkut’s University of Technology Thonburi, Bangkok
(
Thailand
)
2013 International Conference on Alternative Energy in Developing Countries and Emerging Economies
- 568 -
