Journal of Advanced Research in Construction and Urban Architecture
Volume 5, Issue 3&4 - 2020, Pg. No. 14-19
Peer Reviewed Journal
Review Article
Design Determinants and Building
Physiognomies for Low Energy Architecture
in Hot and Arid Regions of India
Mohammad Arif Kamal
Architecture Section, Aligarh Muslim University, Aligarh, Uttar Pradesh, India.
I N F O
A B S T R A C T
E-mail Id:
architectarif@gmail.com
Orcid Id:
https://orcid.org/0000-0001-8302-8794
How to cite this article:
Kamal MA. Design Determinants and Building
Physiognomies for Low Energy Architecture in
Hot and Arid Regions of India. J Adv Res Const
Urban Arch 2020; 5(3&4): 14-19.
Buildings consume a lot of operational energy primarily due to its
cooling requirements. Increasing consumption of energy has led to
global warming resulting in ozone layer depletion. The key to conserving
energy in buildings is to design buildings according to climate. Since most
of the population in India is concentrated in hot arid and composite
climate region, a substantial amount of energy can be conserved using
proper climatic design. The design factors which affect the design of
a residential building in hot arid climate include features like compact
form, orientation, high thermal mass, shading the building, use of
internal courtyards, small openings, evaporative cooling, use of reflective
surfaces etc. These important building design determinants and their
significance in climatic control and conserving energy in residential
buildings in hot and arid regions have been discussed.
Date of Submission: 2020-10-18
Date of Acceptance: 2020-11-23
Keywords:
Climatic Design, Strategy, Low Energy, Residential
Buildings, Hot and Arid Climate
Introduction
There has been a lot of reliance on energy-consuming
technology in cooling and ventilation system to achieve
thermal comfort in buildings, especially in the hot and
dry region. The total amount of energy used in buildings
during operation constitutes a significant part of the total
amount of energy used in a country.1 Housing forms the
most common building type throughout the world. Over
15% of all savings in developing countries is invested in
residential construction. The buildings use one-third of all
energy consumed in India and two-third of all electricity. In
India, the building sector represents about 33% of energy
consumption with the commercial and residential sector
accounting for 8% and 25% respectively.2
Increasing consumption of energy has led to environmental
pollution resulting in global warming and ozone layer
depletion and subsequently having climate change. Since
most of the population is concentrated in the hot and arid
region of India and the housing sector comprising the major
percentage of the building industry, a substantial amount of
energy can be conserved. In this paper, an attempt has been
made to assess three important climatic design strategies
namely shading, thermal mass and courtyard and their
significance in climatic control and conserving energy in
residential buildings in hot and arid regions.
Characteristics of Hot and Arid Climate
Hot and arid climate normally occurs between latitudes
15° and 35° North and South of the equator. In hot dry
climates, there is temperature inversion with large variation
between day and night temperatures. Mean maximum
air temperature for summer months is between 43-48°C
and the minimum is between 27-30°C while in winters
mean maximum air temperature is between 24-30°C and
the minimum is between 17-22°C. The Precipitation is
Journal of Advanced Research in Construction and Urban Architecture (ISSN: 2456-9925)
Copyright (c) 2020: Advanced Research Publications
Kamal MA
J. Adv. Res. Const. Urban Arch. 2020; 5(3&4)
15
slightly low throughout the year from 300-600 mm per
annum with a maximum during the monsoon months. The
sky conditions are normally clear with few clouds with a
luminance of 1700-2500 cd/m2. Solar radiation is direct and
strong during the day, but the absence of clouds permit
the easy release of heat stored during the day time in the
form of long wave radiation towards the night sky. Winds
are usually local often caused by temperature inversion
due to hot ground and cooler upper air resulting in local
whirlwinds. Vegetation is sparse and difficult to maintain
because of the lack of rain and low humidity. Figure 1,
shows the various climatic zones in India and solar path
diagram for the Latitude of 26°N.3
respectively. Building orientation affects the indoor climate
in two respects by its regulation of the influence of two
distinct climate factors:
•
•
Solar radiation and its heating effect on walls and rooms
facing different directions.
Ventilation problems associated with the relation
between the direction of the prevailing winds and
the orientation of the building.
The solar radiation received by a building element
is dependent upon its orientation. The solar radiation
intercepted by the building can be greatly reduced by
choosing a proper building form and by orienting it with
due regard to solar geometry. For an isolated building with
each of the four walls and the roof of equal area, the relative
heat load due to direct solar radiation is given in Table 1. The
amount of solar radiation received on the south-oriented
facade is higher in comparison with other facades in the
northern hemisphere. In addition to the direct radiation,
the building receives diffuse and reflected radiation also.
The measured value of solar radiation shows that during
the summer months in India the diffused radiation is about
one-third of the total radiation and during monsoons, it is
more than half of the total radiation. Irrespective of their
orientation walls receive equal amounts of diffuse radiation
while the roof receives about twice as much.
Table 1.Direct Solar Heat Load on Different Building
Surfaces for Latitudes 17°C To 31°C North and South
Seasons
Roof
Walls
North
South
Figure 1.Various climatic zones of India and solar path
diagram for Latitude 26°N
Summer
48-51% 6-13%
(21st June)
0-2%
Climatic Design Strategies for Residential
Buildings in Hot and Arid Region
Winter
28-34%
(22nd Dec.)
Physiological uncomfortable conditions in arid climates are
mainly caused by the extreme heat and dryness and to a
lesser extent by sand and dust storms. Human thermal
comfort is usually found when the mean skin temperature
is maintained by various means below 33.9°C and above
31.1°C.3 The design factors which affect the design of a
residential building in hot arid climate include features like
compact form, orientation, high thermal mass, shading
the building, use of internal courtyards, small openings,
evaporative cooling, use of reflective surfaces etc. These
important building design determinants for hot and dry
climate have been analysed in this paper.
Orientation of the Buildings
Building orientation is a significant design consideration,
mainly about solar radiation and wind. The orientation
of building means the amount of solar radiation received
on the longer/ shorter axis in summers and winters
0%
East
West
19-20% 19-20%
35-44% 14-15% 14-15%
The Planform Strategy
The planform of a building plays an important role in
ventilation, heat loss and heat gain in the hot and dry
climate. The plan form of a building affects the airflow
around and through it. It could either aid or hinder natural
ventilation. The physical obstacles in the path of the airflow
create pressure differences. This causes a new airflow
pattern. The air tends to flow from high pressure to lowpressure areas. Knowing the direction of air movement, the
plan form can be determined also to create high pressure
and low-pressure areas. Building openings connecting the
high-pressure areas to low-pressure areas would cause
effective natural ventilation. The perimeter to area ratio
of the building is also an important indicator of heat loss
and gain. A large Perimeter to Area (PIA) ratio means that
a small area is being bounded by a large perimeter. A
small P/A ratio means that the same area would be bound by
ISSN: 2456-9925
Kamal MA
J. Adv. Res. Const. Urban Arch. 2020; 5(3&4)
a much smaller perimeter. Greater the P/A ratio the greater
the radiative heat gain during the day and the greater the
heat loss at night. Similarly, the smaller the P/A ratio, the
lesser will the heat gain be during the day and the lesser the
loss at night (Figure 2). Thus, the P/A ratio is an important
factor in controlling heat gain and loss.
Figure 2.Building shape should be of minimum
surface area
Building Form and Surface to Volume Ratio
The volume of space inside a building that needs to be
heated or cooled and its relationship with the area of
the envelope enclosing the volume affect the thermal
performance of the building in the hot and dry climate.
This parameter, known as the S/V (surface-to-volume) ratio
is determined by the building form. The surface area to
volume (S/V) ratio (the three-dimensional extrapolation of
the P/A ratio) is an important factor determining heat loss
and gain. The greater the surface area the more the heat
gain/loss through it. So small S/V ratios imply minimum
heat gain and minimum heat loss (Figure 3). For any given
building volume, the more compact the shapes, the less
wasteful it is in gaining/losing heat. Hence in hot and dry
regions and cold climates, buildings arc compact in for with
a low S/V ratio to reduce heat gain and losses, respectively.
Also, the building determines the airflow pattern around
the building directly affecting its ventilation. The depth of
a building also determines the requirements for artificial
lighting, greater the depth higher the need for artificial light.
16
Effectiveness of Thermal Mass
In hot and dry climates with a large diurnal range, it is
advantageous to use massive building elements. Buildings
with large thermal mass, such as thick-wall stone or
brick structures, damp the diurnal and annual swings in
temperature. The effect of massive construction is to lower
the maximum internal daytime temperature and to raise
the minimum nighttime temperature while in lightweight
construction; the internal temperatures follow closely the
pattern of outdoor temperatures. The importance of heat
storage increases with larger swings in outdoor temperature.
Heat dissipation is then achieved overnight by exposing the
building structure to the cooler night-time outdoor air. The
classical use of thermal mass includes adobe or rammed
earth houses. Its function is highly dependent on marked
diurnal temperature variations. The wall predominantly acts
to retard heat flow from the exterior to the interior during
the day. The high volumetric heat capacity and thickness
prevents heat from reaching the inner surface (Figure 4).
When temperatures fall at night, the walls re-radiate the
heat back into the night sky. In this application, such walls
need to be massive to prevent the ingress of heat into the
interior (Figure 5).
Figure 4.Roof material types for insulation and
increasing the thermal mass
Figure 5.Temperature differential should be created
to achieve time lag
Figure 3.The surface area to volume (S/V) ratio for
different shape types
ISSN: 2456-9925
Hasan Fathy conducted tests on experimental buildings
located at Cairo Building Research Centre, using different
materials. The materials used were mud-brick walls and
roof 50 cm thick and prefabricated concrete panel walls
and roof 10 cm thickness. The thermal performance of the
Kamal MA
J. Adv. Res. Const. Urban Arch. 2020; 5(3&4)
17
two buildings over a 24-hour cycle was monitored. The air
temperature fluctuation inside the mud-brick model did
not exceed 2°C during the 24 hours, varying from 21-23°C
which is within the comfort zone. On the other hand,
the maximum air temperature inside the prefabricated
model reached 36°C, or 13°C higher than the mud-brick
model and 9°C higher than the outdoor air temperature.
The indoor temperature of the prefabricated concrete
room is higher than the thermal comfort level most of the
day.4 Moore reported the temperatures in and around an
adobe building. He observed that when average inside
and outside temperatures are about equal, maximum
interior temperature occurred at about 22:00 hours (about
8 hours after the outside peak). Furthermore, the outside
temperature swing was about 24°C while the interior swing
was about 6°C.5 The effect of thermal mass on interior
temperature is shown in Figure 6.
time lag
energy
swing reduction
day
night
day
day
night
day
(b) Effect of Thermal Mass
(a) Perfectly Conductive Wall
Figure 6.Effect of thermal mass on interior temperature
Table 2.Time lag values of different materials7
Material
Thickness
U-values
Time lag (Hours)
Brick
4
8
12
0.61
0.41
0.31
2–2.5
5–2.5
8–2.5
Concrete
4
8
12
0.85
0.67
0.55
2–2.5
5
8
Insulating
Fiber Board
2
4
0.61
0.09
0.7
0.3
Wood
½
1
2
0.68
0.47
0.30
0.2
0.4
1
Hence the buildings with large thermal mass with light
coloured walls and reflective surfaces are suitable for
climates which require heating in winter and cooling in
summer and can reduce the energy needed considerably,
Other than these passive cooling devices are also used
to reduce the internal temperatures these are mainly of
two types – Radiation cooling and cooling by evaporation.
Active climate control using solar energy in the building is
by use of Air conditioners, Water heaters, Solar Collectors
and Lighting powered by solar power by using Photovoltaic
cells. These can be integrated into the building design on the
roof and south and west walls and can reduce the energy
demand by 2/3rd in a residential building in the hot arid
climate.6 The time lag and U value of different materials
is shown in Table 2.
Relevance of Shading of the Building
The most effective method to cool a building in summer
is to keep the heat from building up in the first place.
The primary source of heat buildup (i.e., gain) is sunlight
absorbed by the building through the roof, walls, and
windows. Specific methods to prevent heat gain include
reflecting heat (i.e., sunlight) away from the building,
blocking the heat, removing built-up heat, and reducing
or eliminating heat-generating sources in the building. The
most important passive cooling strategy, regardless of mass,
is shading. Shading is like putting a hat on the building.
Shading is a simple method to block the sun before it can
get into the building.
Kumar, Garg and Kaushik evaluated the performance of
solar passive cooling techniques such as solar shading,
insulation of building components and air exchange rate.
In their study, they found that a decrease in the indoor
temperature by about 2.5-4.5°C is noticed for solar shading.
The analysis suggested that solar shading is quite useful to
the development of the passive cooling system to maintain
indoor room air temperature lower than the conventional
building without shade.8 Decisions on where and when to
include shading can greatly affect the comfort level inside
a closed space. Shading from the effects of direct solar
radiation can be achieved in many ways:
•
•
•
•
•
Shade provided by the effect of recesses in the external
envelope of the building
Shade provided by static or moveable external blinds
or louvers
Transient shading provided by the orientation of the
building on one or more of its external walls
Permanent or transient shading provided by the
surrounding buildings, screens or vegetation.
Shading of roofs by rolling reflective canvass, earthen
pots, plant cover, vegetation etc.
Although shading of the whole building is beneficial, shading
of the window is crucial. The total solar load consists of
three components; direct, diffuse and reflected radiation
To prevent passive solar heating, when it is not wanted,
a window must always be shaded from the direct solar
component and often so from the diffuse and reflected
components. There are many forms of shading: shutters,
blinds, heavy curtains, trees, other buildings. These can be
used skillfully to keep the heat either inside the building,
outside it or either of these two ways according to the
season.
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Kamal MA
J. Adv. Res. Const. Urban Arch. 2020; 5(3&4)
18
Shading by Overhangs, Louvers and Awnings
Well-designed sun control and shading devices, either as
parts of a building or separately placed from a building
facade, can dramatically reduce building peak heat gain
and cooling requirements and improve the natural lighting
quality of building interiors Figure 7. The design of effective
shading devices will depend on the solar orientation of
a particular building facade. For example, simply fixed
overhangs are very effective at shading south-facing
windows in the summer when sun angles are high. However,
the same horizontal device is ineffective at blocking low
afternoon sun from entering west-facing windows during
peak heat gain periods in the summer. The shading devices
can be classified as given below:
Movable opaque: Roller blind curtains, awnings etc. reduce
solar gains but impede air movement and cut the view.
Louvers: They are adjustable or can be fixed. To a certain
extent impede air movement and provide shade to the
building from the solar radiation.
Fixed: Overhangs provide protection to the wall and opening
against sun and rain.
LIGHT STRUCTURE
TERRACE
LIGHT STRUCTURE
ROOM
COURT
COURTYARD
ROOM
ROOM
HOUSE 1
ROOM
HOUSE 2
STREET
Figure 8.Thermal effect and air movement due
to courtyard
The functioning of the courtyard during the 24-hour cycle
can be subdivided into three phases. In the first phase, cool
night air descends into the courtyard and the surrounding
rooms. The structure, as well as the furniture, are cooled
and remain so until late afternoon. During the second phase,
at midday, the sun strokes the courtyard floor directly.
Some of the warm air begins to rise and also leaks out of
the surrounding rooms. This induces convective currents,
which may provide further comfort. At this phase, the
courtyard acts as a chimney and the outside air is at its
peak temperature. The massive walls do not allow the
external heat to penetrate immediately. The penetration
is delayed and depends on the time lag of the walls. During
the last phase, by late afternoon, the courtyard floor and the
interior rooms become warmer. Most of the trapped cool
air spills out by sunset. After sunset, the air temperature
falls rapidly as the courtyard begins to radiate rapidly to
the clear night sky. Cool night air begins to descend into
the courtyard, completing the cycle.10
Figure 7.Different types of shading devices
The Value of Courtyard
Courtyard planning is a very suitable built form in a hot and
arid climate. Hence they are found in They are generally
centrally located and are completely opened to the clear
sky or partially shaded with overhangs in some of the cases
Figure 8. This also provides shaded spaces which result in
reducing heat gain. The centrally placed courtyard provides
light to all the spaces and also provides air movement
due to induced ventilation through the openings on the
walls facing the courtyard Figure 9. For example, in hothumid seasons, large courtyards provide good ventilation,
especially when opening on to another courtyard or street
such that cross ventilation is promoted. On the other hand,
small courtyards provide more protection against hot, dusty
winds in summers, especially in the hot and arid climate.9
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Figure 9.Provision of courtyard in traditional
architecture in hot dry climate
Effect of Surface Material Characteristics and
Colour
Light colours tend to reduce building heat gain in summer.
Accordingly, light-coloured walls of heavy mass will have
the lowest ETD (equivalent temperature differential) values.
The table below lists typical building finishes and ground
coverings in order of increasing heat reflectivity. Of the total
Kamal MA
J. Adv. Res. Const. Urban Arch. 2020; 5(3&4)
19
radiation incident on an opaque surface, a part is reflected
and a part is absorbed. The reflectivity of the surface is that
part of the total incident radiation, which is reflected while
absorptivity of the surface, is that part of the total radiation,
which is absorbed. Both these properties are wavelength
dependent. In general, it can be said that polished metallic
surfaces are good reflectors at all wave-lengths while light
coloured painted surfaces are good reflectors for solar
radiation but not for thermal radiation.
Emissivity, which defines the radiation emission properties
of a surface at a particular wavelength, is the emissive
power of the surface as compared to the emissive power
of a perfect radiator or black body. For a given wavelength
the surface emissivity equals the absorptivity. However, in
practice, absorptivity is of interest only at wavelengths of
“solar radiation while emissivity is to be measured for farinfra-red wave-length radiation that is emitted by terrestrial
objects. For most materials, these two are not same. The
colour of a surface is a good indicator of absorptivity but not
of emissivity, which depends only upon surface structure.
Whitewash and oxidized Aluminium foil have nearly equal
absorptivity (0.12 and 0.15 respectively) but their emissivity
is very different (0.90 and 0.12 respectively). Table 3, shows
the effect of colour and reflectivity of surfaces of different
materials.11
Table 3.Effect of Colour and Reflectivity for different
material surfaces
S. No.
Materials
% of Total incident
heat reflected
1.
Tar and gravel,
asphalt
7
2.
Slate, dark soil
15
3.
Grass, dry
30
4.
Copper foil:
Tarnished
New
36
75
5.
Paint:
Light gray
Red
Aluminium
Light green
Light cream
White
25
26
46
50
65
75
6.
Whitewash, fresh
snow cover
80
7.
Aluminium foil
95
Conclusion
With the ever-growing global concern for the use of energy
and resources, architects have a greater responsibility
to design environmentally sustainable buildings. With
climate change, we are obliged to come back to systems
and techniques which save energy and which don’t need
much capital. By implementing energy reduction measures,
we can reduce electricity demand and climate-altering
emissions. There are many simple ways in which, without
recourse to new technologies and systems, buildings are
much less wasteful than the overlit, overheated, overcooled,
under-insulated glass prisms that are today’s commercial
norm. However in modern times due to the availability of
electrical power to run active cooling systems, focus on the
use of these techniques had been forgotten. The techniques
discussed in this paper minimize the climatic harshness in
the hot and arid climate and cool the building effectively
and hence dramatically affect building energy performance.
Incorporation of these design determinants would certainly
reduce our dependency on artificial means for thermal
comfort and minimize the environmental problems due
to excessive consumption of energy and other natural
resources and will evolve a built form, which will be more
climate-responsive, more energy-efficient, more sustainable
and more environmentally friendly buildings of tomorrow.
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