Effectiveness of air-well type courtyards on moderating
thermal environments in tropical Chinese Shophouse
Author
Gamage, Wajishani, Lau, Stephen, Qin, Hao, Gou, Zhonghua
Published
2017
Journal Title
Architectural Science Review
DOI
https://doi.org/10.1080/00038628.2017.1383230
Copyright Statement
© 2017 Taylor & Francis. This is an Accepted Manuscript of an article published by
Taylor & Francis in Architectural Science Review on 25 Oct 2017, available online: http://
www.tandfonline.com/10.1080/00038628.2017.1383230
Downloaded from
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ARCHITECTURAL SCIENCE REVIEW, 2017
https://doi.org/10.1080/00038628.2017.1383230
Effectiveness of air-well type courtyards on moderating thermal environments in
tropical Chinese Shophouse
Wajishani Gamage
a
, Stephen Lau
b
,HaoQin
c
and Zhonghua Gou
d
a
Department of Architecture, University of Moratuwa, Moratuwa, Sri Lanka;
b
Department of Architecture, National University of Singapore, Singapore,
Singapore;
c
The Oval Partnership Architecture Ltd, Hong Kong, Hong Kong;
d
School of Environment, Griffith University, Southport, Australia Q1
ABSTRACT
In Southeast Asia with tropical climates, Chinese Shophouse (CSH) as a type of vernacular architecture is
usually equipped with small intermediate air-well type courtyards, also known as ‘Tianjin’, to moderate the
indoor thermal environment. This paper investigates the effectiveness of air-well type courtyards as passive
design strategies on moderating indoor thermal environments in two CSHs located in Malacca, Malaysia.
The study used a field survey and a CFD simulation. Statistical analyses of indoor air temperature and heat
index (HI) measured at different locations of the CSHs show that intermediate spaces next to the air-wells
had significantly lower air temperature and HI. Cross ventilation through the openings on the walls and
air-wells resulted in a significantly lower normalized mean age of air and higher air velocity. The air-well is a
suitable passive design strategy to reduce overheating during daytime and to increase cooling of building
structure during night-time. The air-well courtyards should be arranged in alignment with the prevailing
wind to maximize the cross ventilation and passive cooling.
ARTICLE HISTORY
Received 16 May 2017
Accepted 17 September 2017
KEYWORDS
Thermal environment;
air-well courtyard; Chinese
Shophouses; passive cooling;
energy efficiency
Introduction
In tropical climates cooling and dehumidification accounts for a
major portion of energy consumptions in buildings (Kubota and
Toe 2008). Traditionally natural ventilation has been widely used
in tropical vernacular architecture to regulate the indoor ther-
mal environments (Givoni 1998). The main climatic concern for
buildings in tropics is high temperature, humidity and solar radi-
ation (Olgyay 2015). The core temperature of the human body is
maintained at a particular set point through various physiolog-
ical processes managed by the hypothalamus (Bluyssen 2013).
Under warm conditions vasodilation increases blood flow to the
skin which results in sweating; if ambient humidity is also high,
discomfort occurs due to skin wetness. Therefore, in hot humid
climates increasing ventilation helps enhance sweat evapora-
tion by removing saturated ambient air. Higher air velocities also
provide a psychological cooling effect to occupants and reduce
the discomfort caused by the subjective feeling of skin wetness.
Therefore, tropical vernacular architecture adapts scatter build-
ing layouts to increase wind induced ventilation (Olgyay 2015).
The depth of a building has a significant impact on the effec-
tiveness of natural ventilation. For single-sided ventilation, the
effective depth for natural ventilation is approximately twice
the floor to ceiling height and for cross ventilation the effective
depth is up to five times the floor to ceiling height (CIBSE 2005).
These passive design principles advocate a narrow floor plan for
naturally ventilated buildings.
The Chinese Shophouse (CSH) is a popular vernacular hous-
ing form found in the old cores of tropical port cities in Southeast
Asia (Figure 1). The main design characteristic of a shophouse is
a narrow frontage, deep rears, five-foot-wide covered walkway
CONTACT Zhonghua Gou gouzhonghua@gmail.com, z.gou@griffith.edu.au School of Environment, Griffith University, Southport, Australia
at the front and small internal courtyards. The width is approxi-
mately 4–6 m while the length could be around 30–36 m(Hassan
and Yahaya 2012). The primary ventilation openings of a CSH
are located at front and rear walls (Wang and Jia 2016). Natu-
ral ventilation in this deep and compact house type is assisted
by a small courtyard type termed as ‘Tianjin’ also known as ‘air-
well’ or ‘sky-well’ (Hassan and Yahaya 2012). These air-wells are
used between the functional spaces. Their verticality exceeds
their horizontal dimension to avoid excessive solar radiation. The
area percentage of an air-well on the footprint of a CSH is approx-
imately 5–7% (Knapp and Ong 2013). The functional spaces of
a CSH are symmetrically organized with an axis across several
air-wells and divided vaguely by non-structural partitions or air-
wells. In contrast to the accepted passive design principles in
tropical climates, CSHs are typically arranged in a dense row
layout (Firley and Stahl 2009) (Figure 1) (Figure 2).
The air-well type courtyard found in the Southeast Asian CSHs
has been identified as a fine component of vernacular architec-
ture which extracts passive techniques to moderate the indoor
thermal environment (Zakaria, Kubota, and Toe 2015). The pas-
sive performance of an indoor courtyard in a tropical climate is
primarily dependent on shading and ventilation (Hoseini et al.
2014). In hot humid climates, increased ventilation attributed to
indoor courtyards can enhance sweat evaporation and physio-
logical cooling of the building occupants. Increasing nocturnal
air exchange accelerates the cooling of high thermal mass struc-
ture of a building. This will consequently result in lower indoor air
temperatures during afternoon peak hours (Givoni 1998). Ven-
tilation and infiltration during night and morning hours is the
most favourable strategy to increase structural cooling of high
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2 W. GAMAGE ET AL.
Figure 1. A typical Chinse Shophouse in Penang, Malaysia (by courtesy of Wang and Jia 2016).
Figure 2. Street layout of Chinse Shophouses in Singapore (adapted from Firley
Q13
and Stahl 2009).
thermal mass materials in tropical climates (Sadafi et al. 2011).
Air-well type courtyards used in CSHs that have a height to width
ratio greater than 0.65 may be considered sheltered from the
direct impact of prevailing winds perpendicular to its axis (Jayas-
inghe and Attalage 1999). Therefore, these types of courtyards
may not be able to fully harness the passive cooling attributes
related to wind induced ventilation in the tropics. However, per-
vious research demonstrated that the use of multiple connected
air-wells with staggered form, i.e. courtyards situated between
buildings of different heights, was able to improve cross ventila-
tion and to increase indoor air velocity of intermediate spaces in
the CSH with deep plan (Kubota et al. 2017).
Ventilation could also result from the stack effect. Stack effect
is the movement of air due to the difference of indoor and
outdoor air density as a result of temperature and moisture
differences (Khanal and Lei 2011). In architecture, stack effect
could come from the variation of temperature in courtyards and
the outdoors. As outdoor air temperature tends to be lower
than indoors at night-time, higher temperatures in courtyards
than the outdoors can enhance the stack effect at night-time
(Rajapaksha, Nagai, and Okumiya 2003 ). Toe and Kubota (2015)
demonstrated the stack effect in air-well type courtyards in the
CSH (Figure 3). At night-time, cooled air from the air-well open-
ing flow into the building and cool the internal high thermal
mass structure. During daytime, shading from direct and dif-
fused radiation in the air-wells help to retain the cool air at
lower level for a longer time period. Less-heated air at lower
levels of the air-well prevented vertical air exchange with hot
outdoor air. This results in lower indoor air temperature during
daytime peak hours. In tropical climates as larger and shallower
courtyards result in more heat gain and higher indoor air tem-
peratures of adjacent spaces during the afternoon peak hours,
deeper and more elongated courtyards with higher shading per-
centage is preferable (Martinelli and Matzarakis 2017). In these
regions, the shading of the courtyard is mainly dependent on
its depth rather than its elongation (Muhaisen 2006). A com-
parison study of thermal environments in 16 air-well c ourtyards
in Malacca reveals that daily maximum air temperature in the
air-well is mainly influenced by its openness and depth (Kubota
et al. 2017). Closed and deep air-wells with higher shading were
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ARCHITECTURAL SCIENCE REVIEW 3
Figure 3. Conceptual illustrations of passive cooling by air-well type courtyard: (a) daytime and (b) night (adapted from Toe and Kubota 2015).
able to maintain lower indoor air temperatures during daytime
peak hours.
The air-well type courtyards used in the Southeast Asian CSHs
compliments its long narrow form. These air-wells have some
features which are climatically appropriate for the hot humid
regions, as well as some features which may hinder the optimum
thermal comfort performance of an indoor courtyard in this cli-
mate. Research is needed to understand the effectiveness of the
air-well type courtyard on moderating indoor thermal environ-
ment in these tropical CSHs. This study uses a filed investigation
to explore variations of indoor thermal environment attributed
to air-well courtyards in CSHs. Furthermore, a CFD (Computer
Fluid Dynamics) simulation is used to investigate the impact
of prevailing wind on passive cooling potential of the air-well
courtyards.
Methodology
The city of Malacca and selected shophouses
Malacca is a tropical city located at 2°11
45
N, 102°14
25
E.
According to the city’s weather record, climate variables, such as
temperature and relative humidity, do not show large monthly
variations (Toe and Kubota 2015). However, many variables
exhibit prominent diurnal variations from hour to hour, indicat-
ing the strong influence of solar radiation on the local climate.
The seasonal climatic change is dominated by the monsoons.
Malacca was once a small and remote fishing village and
began to develop as a port city in the fourteenth century. Many
CSHs which date back to the seventeenth and eighteenth cen-
tury can be found within the core zone of this historic city. Sev-
eral categories of CSHs’ are found in Malacca, and their spatial
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4 W. GAMAGE ET AL.
Figure 4. Ground floor layout plan of CSH: (a) CSH in Malacca (adapted from Tan 1988), (b) CSH in Singapore (adapted from Davison and Tettoni 2011), and (c) CSH in
Penang (adapted from Omar and Syed-Fadzil 2011).
Figure 5. House 1 and 2: (a) Location; (b) front exterior view (Source: Google Earth, imagery dated on 18 January 2015).
planning, form and architectural design are comparable (Tan
1988). The CSH found in Malacca typically has two or more halls
with intermediate air-wells and a fenced backyard (Davison and
Tettoni 2011). These CSHs’ like others found in the old cores of
tropical port cities such as Singapore, Penang and Batavia have
simple elongated plans, multiple air-wells and narrow corridors
(Omar and Syed-Fadzil 2011) (Figure 4).
Two CSHs are selected for this survey; they are located at
54–56 Jalan Tun Tan Cheng Lock in the core of the city. The
two houses are adjoined by a party wall (Figure 5). House 1 has
two air-well type courtyards and a large backyard. House 2 has
one air-well type courtyard and a backyard. The two houses are
inter-connected on both levels. The two houses are located in
a cluster of CSHs with similar configuration (Figure 6). It is a
densely built up neighbourhood, with a gross building cover-
age ratio of 76%. There are no high-rise buildings surrounding
the site. The prevailing wind is in parallel to the building ori-
entation. Therefore, the influence of the incoming wind from
the surrounding environment was considered relatively insignif-
icant. The two shophouses were donated to the Department of
Architecture, National University of Singapore to function as a
Centre for Asian Architectural and Urban Heritage in Malacca.
They have been well preserved to emulate the original spatial
planning, form and architectural design of a typical CSH found
in most tropical port cities in Southeast Asia.
Figure 6. Site condition and prevailing wind (drawn by the authors).
Field measurement
The field measurement was conducted in April 2016. The mea-
sured period can be considered as a representative of a fair
weather day in Malacca. For the purpose of this study, afair
weather day in a month is used as a representation of aver-
age conditions in terms of air temperature in Malacca city. Fair
weather days include clear and intermediate sky conditions with