The concerns over global warming and need for reduction of high emission
of greenhouse gases, demand the utilization of strategies for indoor climate
modification in promoting comfortable indoor environment (Givoni, 1994).
In warm humid tropics overheated building interior are common due to solar
penetration through the buildings envelope and windows (Rajapaksha et
al., 2003) and terrace houses as one of the most common typologies
of residential buildings in Malaysia are also facing these problems. Because
of the high density of the building blocks and the crowded dwellings a
large number of buildings do not fulfill the requirements for thermally
comfortable environment. So far many bioclimatic design strategies have
been proposed in different studies and some of them are also used in practice
(Budaiwi, 2006). One of the common strategies is to include internal courtyard
in the house in order to introduce the out doors in to the heart of the
buildings core as well as optimizing the climatic source. Solar radiation
which received to the courtyard surfaces will affect the thermal performance
of the building especially in areas adjacent to courtyard. The amount
of heat gain through radiation depends on climatic condition, the time
during the year and configuration of the courtyard (Muhaisen and Gadi,
2006). Moreover, thermal performance of courtyard building has been investigated
by many researchers such as; Al-Hemiddi and Megren Al-Saud (2001), Rajapaksha
et al. (2003), Ratti et al. (2003) and Muhaisen (2006).
But normally mentioned studies have evaluated buildings as common bungalows
without the limitation for land size and opening, in different countries
(Japan, UK, Saudi Arabia). This study intended to investigate the influence
and effectiveness of internal courtyard on thermal performance of terrace
houses in Malaysia, in order to take the advantages and offer recommendations.
To this end, ECOTECT software is used to simulate thermal and shading
performance of the case study building. Ecotect is a powerful tool to
simulate the environmental effects on building`s internal condition. Similarly
Al-Sallal (2007), Krüger and Dorigo (2008), Kharrufa and Adil (2008)
and Alexandri and Jones (2008) have used this software to evaluate the
required design configurations in their studies.
The study area is located in Kuala Lumpur, which is situated at latitude
3° 7` above the equator and longitude 101° 33`. Being close to
the equator, the hot and humid conditions are emphasized with heavy rain
fall and sunshine throughout the year.
||Case study building, plans (a, b) and section (c)
It has a yearly mean temperature of about 27°C and relative humidity
(RH) of 70 to 90% throughout the year (Sabarinah and Hyde, 2002). Moreover,
the monthly mean of maximum temperatures values ranged from 33.5°C
on March and April to 31.9°C on December, while monthly mean of minimum
temperatures values ranged from 23.1°C on January to 24.3°C on
May (Malaysian Metrological Service, 2007).
THERMAL MODELING TOOL
There are different computer tools for building thermal modeling with different
simulation methods. ECOTECT is a complete building design and environmental
analysis tool that covers the broad range of simulation and analysis functions,
when it is required to truly understand how a building design will operate and
perform (Marsh, 2003). It couples an intuitive 3D modeling interface with extensive
solar, thermal, lighting, acoustic and cost analysis functions. ECOTECT is one
of the few tools in which performance analysis is simple, accurate and most
importantly, visually responsive. For analyzing the output ECOTECT use a wide
range of informative graphing methods which can be saved as Metafiles, Bitmaps
or animations. Tables of data can also be easily exported to; RADIANCE, POV
Ray, VRML, AutoCAD DXF, EnergyPlus, AIOLOS, HTB2, CheNATH, ESP-r, ASCII Mod
files and XML.
A case study terrace house has been considered for modeling and evaluation
of thermal condition (Fig. 1). The two stories of the
house consist of:
||Ground level: This level is for family area of
the house. The thermal zones were divided in to 5 zones: (1) the kitchen,
(2) dining area, (3) living area, (4) utility, (5) the front yard
which considered as out side zone.
||First level: This level is for bedrooms and bathrooms of
the house and the created zones are for: (1) Master Bed room, (2)
Bed room 1, (3) Bed room 2, (4) The staircase, (5) The Roof. The main
bath room has been considered in the staircase zone and the other
one in the master bedroom zone.
Materials: For Ecotect model materials for the building are either
chosen from Ecotect library or created from user library (Table
1). The property values for these materials are calculated from Ecotect
material property. The materials of the house are considered as follows:
First investigation for thermal performance of the house as it exists
was conducted for three different months of the year (March, Jun and December)
||Material description for the case study building
||Case study terrace house after introducing the courtyard
In the next step after investigating common typologies of terrace houses
with courtyard, a rectangular shape courtyard with 2.2H2.5 m dimension,
has been introduced in the house. Figure 2 shows the
case study terrace house model after including the courtyard in the family
area (Mode B). As could be seen, the court yard zone is adjacent to the
living and dining zones.
The evaluation of thermal performance for the adjoining zones was repeated
after introducing the courtyard.
RESULTS AND DISCUSSION
In mode A results showed that noon hours are normally critical times
as higher internal temperatures are experienced during these hours according
to the sun`s beams angle and penetration in to the house.
According to temperature variations of the living area in mode B, introducing
the internal courtyard in the house has distinctly affected the thermal
conditions in this area. Figure 3 shows the comparison
between temperature variations of living area for mode A and B. The temperature
has decreased (less than 1°C) all the times after including the courtyard
||Temperature difference between mode A and B in March
||Conduction gains difference of mode A and B for living
It is clear that after introducing the internal courtyard in this area
the overall UA value has increased because ofthe added windows (high U-value)
to the walls adjacent to the courtyard, which will cause the temperature
decrease. Figure 4 also displays the difference between
hourly conduction heat gains of the living area in Mode A and B.
It is perceivable that although the conduction gains -including the window-have
increased in mode B around noon hours, since the living zone is naturally
ventilated; increasing ventilation and heat loss in morning hours will
help for temperature decrease (Fig. 5). As could be seen
conduction gains in living area has also decreased at morning hours in
mode B, which shows the heat releasing through the windows at these hours.
||Heat gain and loss through ventilation for mode A and
||Temperature difference between mode A and B for living
area in Jun
||Temperature difference between mode A and B for dining
area in Jun
Figure 6 shows the temperature difference of Mode A
and B in Jun. there is evidence that the temperature has decreased.
According to hourly heat gains analysis after introducing the courtyard
the inter-zonal heat gains of the living area have increased so, in order
to have a more accurate analysis thermal performance of dining area which
is the adjacent zone to living area and courtyard has been considered.
Figure 7 shows the temperature difference for dining
area in mode A and B in Jun. As could be seen internal temperature in
dining zone has increased all the times during the day and night after
introducing the courtyard.
||Solar gains difference of dining area for mode A and
B in Jun
||Temperature difference between mode A and B in December
for living area
Figure 8 shows the difference of solar gains in dining
area for mode A and B. It is perceivable that dining area will receive
much more solar heat after introducing the courtyard, from the window
adjacent to the courtyard and since this zone does not have enough openings
to release the heat, afterwards it will share its heat with its adjacent
zones (living area) and cause the increase in inter-zonal heat gains of
the living area.
The results for temperature variations of living area in December shows
that the temperature has decreased in compare with Mode A again, while
the temperature of the dining area has increased the same as two other
months (March and Jun) (Fig. 9).
So it has been perceived that introducing the internal courtyard will
somehow enhance the thermal condition of the living area by increasing
natural ventilation and internal heat release through its windows. But
as it will increase the solar heat gains of the dining area and since
this zone does not have enough opening to release the heat, the temperature
will increase in this zone and make it hotter. In return dining area will
try to share this heat with living zone so will reduce the cooling effects
of the courtyard in this area.
Shaded courtyard: In the next step a shading roof was considered
for the courtyard in order to examine its effects on heat absorption of
the fabrics and thermal conditions of the zones adjusted to it.
||Temperature difference for living area with different
height for courtyard roof
||Courtyard with roof
||Solar gains difference for courtyard with and without
the shading roof
trying different heights for the shading roof (250, 500 and 1000 m) the
height of 500 mm seemed more suitable for shading the courtyard area as
well as letting the indoor hot air to be discharged into the sky. Figure
10 shows the temperature difference of the living area after testing
different height for the shading roof. As could be seen living area will
experienced lowest internal temperature when the roof has the height of
500 mm (Fig. 11).
According to thermal analysis, adding the shading roof for the courtyard
will decrease the solar heat gains in this area (Fig. 12)
which will accordingly cause the improvement in thermal condition of the
||Temperature difference for living area with shaded and
unshaded courtyard in Jun
||Temperature difference of the living area after changing
the material of the party walls with courtyard
Figure 13 displays the temperature difference of the
living area for mode B and courtyard with shading roof in Jun. As could
be seen added shading roof for the courtyard will change the thermal condition
of the adjacent zones especially around noon and afternoon hours. The
decrease in solar heat gains of the adjacent walls after including the
roof for courtyard, could be the main reason.
Material: Next step is to analyze the thermal performance of the
living area when the material of the walls surrounded the courtyard has
been changed. Instead of common materials (brick and plaster: 110 mm brick
with 10 mm plaster either side) with U-value of 2.62 w/m2k,
materials with lower U-Value (1.15 w/m2k) were chosen (aeratedConcBlkPlaster:
10 mm aerated plus, 220 mm concrete block with 10 mm plaster inside).
Results shows changes in temperature variation of the living area, as
Fig. 14 displays the temperature has decreased around
noon hours which is considered as critical times, while in the morning
and afternoon hours little increase in temperature is perceivable. Although
the temperature still has its acceptable range (27 to 27.5°C). The
reason is because of the increase in the width of the wall for second
material which increased the effects of thermal mass. As this area is
normally being used during the day hours it could be acceptable, while
for the zones such as bedrooms which are used during night hours, lighter
materials are preferable because of their short time lag which let the
heat to disperse quickly to the outdoors and decrease the indoor temperature.
Including an internal courtyard in the terrace houses of tropical climate
has significant effects on the thermal performance of indoor spaces specially
the areas adjacent to the courtyard. The results obtained from computational
analysis (Ecotect) revealed the potential thermal impacts of courtyard
for passive cooling in double story terrace houses located in tropical
climate. It has been explored that, since the zones adjacent to courtyard
with suitable openings in two sides will be able to release the heat through
natural ventilation, they will experience better thermal condition after
introducing the courtyard. Whereas in the areas with openings just to
the courtyard the penetrated heat through solar radiation will make the
zone hotter. This extra heat tries to be released in the adjoining areas
and increase their internal temperature. So considering the internal relations
of the areas in courtyard housing seemed necessary. Also in order to lessen
the influences of solar radiation which will penetrate in the house through
the internal courtyard, suitable shading devices as well as suitable materials
for its walls are suggested. More detailed studies on appropriate materials
for different areas adjacent to the courtyard, in terrace houses of tropical
climate seemed requisite.