Daylighting and shading for thermal comfort in Malaysian buildings.
A study on the potential of daylighting as a source of indoor lighting in Malaysian
buildings is described. Not much work has been done on daylighting in Malaysia, due
to several factors. Firstly, local daylight data is unavailable and secondly, research in
daylighting design is relatively new. This work is therefore aimed at providing a solid
foundation in daylighting knowledge and to contribute towards the development of
deSign tools and strategies for buildings in a hot, humid climate, in particular
Malaysia. The work began with a survey of traditional and modern buildings to
identify old and new daylighting techniques. From the daylighting point of view,
recently built buildings in general, are not designed for the tropics. The bioclimatic
approach was used to identify the passive strategies to keep Malaysian buildings
thermally comfortable for the occupants. The Model Year Climate accurate hourly
data for 8 climate parameters were produced by statistical analyses from a database
of 21 years of meteorological data. A field study to determine the thermal comfort
conditions of young persons in a normal working environment was also carried as
part of the bioclimatic analyses. From the results of the three studies, a strategy was
formulated to create a low-energy yet thermally comfortable building environment for
the hot-humid region by integrating daylighting in the building design through the size
of window openings and types of shading devices.
The prevailing sky type in the Klang Valley was determined using solar irradiation
and cloud cover data. The sky type was identified, and confirmed by four
identification techniques, as predominantly intermediate. As daylight and solar
irradiation share similar physical properties, hourly daylight data were modelled using
solar irradiation data and luminous efficacy values. An artificial sky was designed
and constructed to conduct daylighting experiments using architectural scale models.
The correlation coefficient of the luminance produced by the sky simulator as
compared to the intermediate sky luminance model was 0.996. This study focussed
on sidelighting, which is the most common daylighting strategy in Malaysia. The
daylighting performance of several window opening sizes ranging from 10% up to
40% window-to-wall ratio and several types of shading devices were investigated
using the Daylight Factor Method. A suitable architectural scale model of a basic
room with one removable wall, on which the fenestration systems were attached,
was used for the investigations. The optimum window opening size was found to be
25% where daylight is enhanced and energy consumption for cooling load is
reduced. The best shading device tested for buildings in the Malaysian climate was
found to be a sloped shading device integrated with a horizontal light shelf. This
device has the capability to reduce excess lighting while maintaining the required
daylight levels in a normal working environment as recommended by the Malaysia
Guidelines for Energy Efficiency in Buildings.
The results of the daylighting performance of the fenestrations were used together
with modelled exterior illuminance data to produce several daylighting design tools.
Graphical tools produced to aid architects include iso-OF charts, isolux charts or
daylight footprints while look-up tables and nomographs were produced for
engineers. The NORMA algorithm was used to calculate the cooling loads of a
simple building to demonstrate the possible energy savings as a result of applying
the above daylighting strategies. It was found that at least 10% of energy could be
saved by integrating daylighting in Malaysian buildings while maintaining acceptable
indoor thermal comfort criteria for young Malaysians.