WEATHER and climate exercise tremendous influence over
human wellbeing and health. Humans make dwellings for
themselves to escape the vagaries of climatic variations. Sitting
in the relative comfort of our airconclitioned offices and
homes - between a past in which electricity was unimaginable and a future in which it probably will be unaffordable -
we are forced to ask whether the price that we are willing to
pay for our modern lifestyles is too high.
Living well beyond our means today, we have, with total
unconcern, relegated our problems of energy to the back-
ground. It is time we realised that as
humans, it is our responsibility to put a
stop to the exploitation of the irreplenishable - whether energy, environment, flora
and fauna, or archeological sites. Conservation is the watchword today.
The '70s oil crisis forced the international community
to think seriously of conserving energy. According to
calculations, the building industry was the major consumer
of energy; almost Ii3rd of the total energy consumed in the
us was used for heating and cooling the country's buildings, leading to the rediscovery of the sun, wind, water
and biomass as natural methods of controlling temperature. The term "solar passive architecture" was coined
during this period. However, traditional systems cannot compare favourably with modern airconditioners. As their limitations became apparent, people lost interest and architects dismissed them as being "too expensive". The high cost of energy
came to be accepted as another inevitability of day-to-day
existence.
Undoubtedly, our requirements today are greater than
what our foreparents needed 100 years ago. Compared to
airtonditioners, solar passive architecture is expensive and
ineffective in most climates. On the other hand, it can help
reduce the load on an airconditioning system by over 25 per
cent. Every region in the world offers excellent examples of
naturally cooled or heated buildings, be it the igloos of the
Eskimos, or the Mesa Verde native American settlerent in
Colorado, USA.
Humans, when confronted with extreme climates, have
usually exploited any one of the 4 factors which affect their
thermal comfort - the movement of air, temperature, relative
humidity and radiation. For example,
prevailing wind and breezes are
utilised in a dry climate. By properly
orienting and locating a building, the
Hot air cools on
coming in wind can be directed into it using
contact with windcatchers and windtowers, which
cool tower have been the subjects of much experimentation recently.
The exchange of heat between a
bullding and the air surrounding it
Tower is depends, among other things, on the
cool during velocity of the air; the greater the
speed of air, the greater will be the
'heet exchange. Consequently, to
rernove heat from a building, the pencool air etration of wind should be facilitated.
descends It has been observed that the quality
of the surfaces over which a wind
blows before coming in contact with
the building affects its temperature.
Ground Evaporation cools a hot wind when it
level
is passing over a water basin.
Traditional buildings paid con
siderable attention to the pretreat
ment of ventilated air. The use of wet grass mats for filtering
air was common practice (as in the Diwan-i-Khas in Red Fort,
Pancha Mahal in Fatehpur Sikri and Deegh Palace near
Bharatpur). Some traditional buildings in Iran, particularly in
the deserts, make use of interesting devices and concepts. In
addition to thick mud walls, which stabilise interior tempera
tures to an intermediate value between day and night levels,
and the construction of buildings close to each other to reduce
exposure to the sun and heat losses at night, Iranians use baud
geers, or windtowers.
A windtower is made of a large chimney vertically slit in its
upper part by several brick baffles. At night, the tower cools,
thus cooling the air coming in contact with it, which becomes
heavier and descends to the interior of the tower and the
building. On windy ddys, the process is accelerated. The air
enters through the tower, descends and passes through the
building, and exits from the doors that face the central hall and
the basement. The pressure created by the cool air pushes the
hot air out of the building.
Heat absorbed by the tower during the day is transmitted to
the air at night, creating an ascending current when there is
need for further cooling. This current can be employed"to suck
fresh air into the building. On a windy night, the air flows
down the side of the tower which is exposed to the wind and is
warmed by the contact with the masonry, while an upward
current is generated in the leeward section of the tower. By
appropriately opening or closing various sections of the tower
and/or of the building, different portions of the building can
be cooled as and when required.
A windtower's range of applicability has been increased by
using the knowledge that the temperature deep inside the
earth remains nearly constant; daily temperature variations
hardly affect it at a depth of more than I metre, while seasonal variations are dampened by
the earth. The earth's temperature is influenced by the
annual ambient temperature
variations with a time delay of
several months. It has been
seen that in Delhi the temperature of the earth 4-5 in below
ground level remains constant
throughout the year, and is
equal to the main annual
Sol-air temperature (temperature of the earth, which is
around 22'c-23'c).
The earth can be used as a
source or a sink for heat, for heat
exchanger system utilises the earth's stable
temperature and large thermal capacity. The
air that is passed through the pipe
ground level is cooled in summer
in winter. The amount of heat
between the air and the tunne
depends on factors such as the lenj
of the tunnel, the material of the
air velocity, etc.
Some energy-conscious India
have used the concept of the win,
Delhi Energy Development Agen
designed by Rayal Designers, use
tunnel system. Here, a 500 mm-dh
windtower fixed with
50 m long, connects the
a blower to a 300 mm-diameter ring pipe; the connecting
pipes enter the rooms below sill level. Being a relatively new
concept, data on its performance is not available.
Architect Vinod Gupta, well-known for his cmc building in Bombay, has used the windtower to attract cool
southwest winds in a hostel building in Jodhpur. An experimental windtunnel system has also been erected in the
Indian Institute of Technology campus in New Delhi
under the guidance of N K Barisal, professor at the Indian
Institute of Techikology, Delhi.
However, windtowers and windtunnels only assist in lowering the air temperature, without affecting the water vapour
content of the air. Water, which helps in evaporative cooling,
increases the cumulative effect of the system. When cool air
comes in contact with water, some water is evaporated, thus
lowering the temperature of the air and increasing its water
vapour content. A windtunnel system that cools air evaporatively as well is particularly effective.
An Iranian windtower needs to be surrounded closely by
buildings to ensure that the wind does not turn around and
escape through the tower. Also, it works only with individual
units. The windtunnel system is free from these limitations,
although the accumulation of dust and the difficulty of protection from driving rain create problems. The additional
advantage is that the system works during powercuts.
The Irani ;ans also use windtowers for keeping rainwater
fresh in underground roofed tanks, covered by vaults at
ground level. In order to keep the water fresh, custom designed windtowers are built around the tank to carry air
down to the surface of the
water. The system utilises the
seasonal variations of the
desert area and the insulating
characteristics of the ground,
iwhich maintain a constant
temperature throughout the
year. External heat does not
penetrate the lower levels of
the reservoir, and large
Amounts of water remain cool
during the torrid summers.
The concept of the windt6wer had been found to be so
-feasible in Iran that each house
;equhnce was equipped with one,
iouses had several. However, modcts, trained in Western planning
ave contributed to the disintegravhole pattern. Technology needs to
refully in specific environments;
to use an imported technology has
mistaking the means for the goal.
Skyscrapers as well as steel-and-glass struc[nctionality because of climatic factors such as sands
is sand, dust and winds, which
tter with altitude, and the lack of
ditional architecture like stone
ial gardens and semi-underground
ith natural ventilation through
not only provide thermal insulaprotection against sand and dust, but
tion and
also help to generate air currents that moderate temperature.
Cylindrical roofs, vaults and domes diminish the surface area
exposed to the sun and help control temperatures. Even
though the most primitive solution is not always the best, one
must not abandon the wisdom bequeathed by tradition at the
drop of a hat.
---Ratish Nanda is member of the Conservation Society of Delhi.