Air moving in and through building: historical prototypes
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International Workshop on Energy Performance and Environmental 1 Quality of Buildings, July 2006, Milos island, Greece Air moving in and through building: historical prototypes and contempo- rary applications K. Saranti School of Architecture, University of Patras, Greece ABSTRACT This paper attempts to organise examples of building features for air cooling in historical ar- chitecture in categories based on the manner in which the air is channelled in or through the building. Contemporary building applications that bear reference to historical methods have also been searched and presented. This research has shown that historical prototypes and con- temporary applications both can be used to im- prove natural ventilation and cooling of build- ings. 1. INTRODUCTION Modern heating and cooling equipment play a significant role in thermal comfort. Unfortu- nately the extensive use of that equipment has caused not only significant electrical consump- tion but also contamination of the environment. There are plenty examples of vernacular archi- tecture which show that pleasant conditions can also be caused naturally. Such examples are seen in settlings of Iran, Iraq, Saudi Arabia, North Africa, but also in some regions in Greece such as the Cycladic islands. What is to be an- swered is if those examples which compose the historical prototypes can be applied nowadays, if they have already been applied, if they were efficient and if the contemporary applications constitute an evolution of historical prototypes or innovative approaches. On an effort to pro- vide an answer to these questions this paper or- ganises historical and contemporary applica- tions in accordance with the movement of air in or through them. 2. AIR MOVING IN A VERTICAL STRUC- TURAL DEVICE (BADGIR/WIND CATCHER) Badgirs were traditional devices which used to ventilate and cool buildings in hot and arid cli- mate regions (Iran, Iraq, Middle East etc). They were like chimneys, the end of which was prop- erly designed with openings oriented to the di- rection of the prevailing winds of the region. In- ternally, two partitions were placed diagonally across each other down the length of the device. This design, externally and internally, helped to capture and canalize the prevailing winds to the interior of the building for the ventilation and cooling of the building (Fig. 1). The efficiency of badgir as a historical proto- type will be better understood if studied together with similar contemporary constructions. So, as at the old days the constructors and the inhabi- Figure 1: Plan and section of the badger.
Air moving in and through building: historical prototypes
Microsoft Word - Saranti.docInternational Workshop on Energy
Performance and Environmental 1 Quality of Buildings, July 2006,
Milos island, Greece
Air moving in and through building: historical prototypes and
contempo- rary applications
K. Saranti School of Architecture, University of Patras, Greece
ABSTRACT This paper attempts to organise examples of building
features for air cooling in historical ar- chitecture in categories
based on the manner in which the air is channelled in or through
the building. Contemporary building applications that bear
reference to historical methods have also been searched and
presented. This research has shown that historical prototypes and
con- temporary applications both can be used to im- prove natural
ventilation and cooling of build- ings.
1. INTRODUCTION Modern heating and cooling equipment play a
significant role in thermal comfort. Unfortu- nately the extensive
use of that equipment has caused not only significant electrical
consump- tion but also contamination of the environment. There are
plenty examples of vernacular archi- tecture which show that
pleasant conditions can also be caused naturally. Such examples are
seen in settlings of Iran, Iraq, Saudi Arabia, North Africa, but
also in some regions in Greece such as the Cycladic islands. What
is to be an- swered is if those examples which compose the
historical prototypes can be applied nowadays, if they have already
been applied, if they were efficient and if the contemporary
applications constitute an evolution of historical prototypes or
innovative approaches. On an effort to pro- vide an answer to these
questions this paper or- ganises historical and contemporary
applica- tions in accordance with the movement of air in or through
them.
2. AIR MOVING IN A VERTICAL STRUC- TURAL DEVICE (BADGIR/WIND
CATCHER) Badgirs were traditional devices which used to ventilate
and cool buildings in hot and arid cli- mate regions (Iran, Iraq,
Middle East etc). They were like chimneys, the end of which was
prop- erly designed with openings oriented to the di- rection of
the prevailing winds of the region. In- ternally, two partitions
were placed diagonally across each other down the length of the
device. This design, externally and internally, helped to capture
and canalize the prevailing winds to the interior of the building
for the ventilation and cooling of the building (Fig. 1).
The efficiency of badgir as a historical proto- type will be better
understood if studied together with similar contemporary
constructions. So, as at the old days the constructors and the
inhabi-
Figure 1: Plan and section of the badger.
2 International Workshop on Energy Performance and Environmental
Quality of Buildings, July 2006, Milos island, Greece
tants had understood that proper opening with the proper
orientation was required. As a result, there where different types
of badgirs (Paki- stani, Egyptian, Iranian etc) (Fig. 2). Respec-
tively, nowadays, as long as the supply of air is not stable,
researches try to invent the most effi- cient design which would
diminish the air resis- tance developed during the movement of air
in the badgir (Fig. 3).
The placement and the orientation of the badgir was another factor
which was proved fundamental for the cooling of a building. For
this reason, it was often placed over water tanks or fountains so
as to cool the passing air by evaporation (Fig. 4) In the Pavillion
of Bagh-e Khan in Yazd, Iran the air passed through un- derground
tunnels. The lower temperature of the ground compared to the
external, along with the presence of the underground water caused
the reduction of the temperature of the air that en- tered the
building.
Nowadays, fountains and tanks of water have been replaced by
special filters -dampers- which
are damp causing the same results (cooling by evaporation). Another
way of cooling is achieved with the help of sprays (as long as the
construction permits it). In that situation, drops of water flow
down the length of the badgir (the result of cooling depends on
different factors such as the velocity of the air in relation to
the droplets, the humidity etc) (Fig. 6).
3. AIR MOVING IN AN OPEN SPACE SUR- ROUNDED BY A BUILDING (COURT-
YARD) Courtyards are formations that are used by the people since
the time they started living in buildings. Courtyards are known not
only be- cause they worked as climatic regulators but also because
of the private environment they created.
Figure 2: Catching efficiency for different Wind Catcher design
(historical prototypes).
Figure 3: Catching efficiency for different Wind Catcher design
(contemporary applications).
Figure 4: Wind-catcher used in old houses in Cairrene, Egypt. Air
is drawn down and through an interior fountain which cool the air
by evaporation.
Figure 5: Section of the badgir at the Bagh-e Khan, Yazd.
International Workshop on Energy Performance and Environmental 3
Quality of Buildings, July 2006, Milos island, Greece
Relation of air and the courtyard According to Fuller Moore in his
book Envi- ronmental Control Systems, the courtyards function in
three phases during a day, as seen at Figure 7.
Apart from the three thermal phases of the courtyard of Fuller
Moore, G. Z Brown and Mark Dekay in their book Sun, Wind, Light
pro-
pose another categorisation of the courtyards according to the need
for presence of wind or protection from it. In the first case-when
the wind in it is needed- the building that surrounds the courtyard
has to be short and the courtyard itself has to be open and broad.
In the opposite case-when the protection from the wind is needed-
the building that surrounds the court- yard has to be tall and the
courtyard itself has to be close and small compared to the height
of the surrounding building. As we can see at Figure 8, the smaller
the ratio between the height of the surrounding building and the
length of the courtyard in the cross section along the move- ment
of air, the bigger the presence of air.
Furthermore, there are often factors which also contribute in the
conditions in the court- yard, such as the arrangement of the
openings of the building which surrounds it, the location of trees
that are planted, the presence of fountains or water tanks
etc.
4. AIR MOVING THROUGH A PERFO- RATED SURFACE (MASHRABIYAS-
ROWSHANS) Mashrabiyas were traditional architectural pro- totypes
which were used to control natural ven- tilation and lighting. They
were first seen in the west districts of Saudi Arabia and
afterwards in many regions with hot-arid and hot-humid cli-
mate.
Rowshans were according to Hassan Fathy «…wooden lattice screens
composed of small wooden balusters that were circular in section
and arranged at specific regular intervals, often in a decorative
and intricate geometric pat- tern…» (Fig. 9). They were placed at
the finish- ing of an opening, sometimes smaller (row- shans) and
other times bigger, even at the finish- ing of a whole façade
(mashrabiyas) (Fig. 10). Because of their construction, and their
place- ment they contributed in the control of ventila- tion,
lighting, humidity, in the cooling of water and also they ensured
privacy.
With regard to ventilation, these perforated surfaces, because of
their gaps, regulated the ve- locity of the incoming wind and the
amount of it, and at the same time they contributed in the
reduction of the humidity while the external humid air moved
through the surface (especially at night), part of the molecules of
humid were
Figure 6: Contemporary ways of cooling the air by evapo- ration.
Left: dampers, Right: spraying.
Figure 7: Diagrammatic explanation of the three thermal phases of a
courtyard.
Figure 8: Sizing courtyards for ventilation. Average wind speeds as
a percentage of free unobstructed incident wind (%).
4 International Workshop on Energy Performance and Environmental
Quality of Buildings, July 2006, Milos island, Greece
absorbed by the wooden surface. Furthermore, when the external air
was arid and the solar rays fall on that surface, then part of the
humidity was given to the interior of the building.
5. AIR MOVING THROUGH PARALLEL SURFACES (DOUBLE SKIN FACADES) As in
mashrabiyas, in our days a similar appli- cation is encountered
when perforated surfaces are placed parallel to the façade panels.
The re- sulting parallel surfaces (double skin facades) present
many advantages concerning the ther- mal comfort.
The outer skin acts as a screen against high- speed winds, thereby
allowing the natural venti- lation of the building. Sun shading can
be in- stalled in a simple form behind the outer façade layer,
where it is protected from the elements and easily accessible. The
buffer effect created by the corridor space between the two façade
skins and the high resistance to thermal trans- mission provided by
the two layers of glazing help to reduce the effects of insolation
near the surface of the inner façade and increase the sense of
comfort in the rooms (Fig. 12).
6. AIR MOVING THROUGH GAPS IN FULL FACADES (CLAUSTRA) Gapes in full
facades are seen in many buildings in regions with hot-arid climate
for controlling ventilation and lighting (Fig. 13). In Greece and
specifically in the Cycladic islands, they are called “feggites or
marmara” and are often placed high in a wall for assuring a
controlled flow of air in the interior without an intense in-
crease of temperature which would cause a big- ger opening (Fig.
14). The specific position was a result of the prevailing winds of
the region. At the same time, they were placed high in a façade in
order to capture as fresh air as possible. The inhabitants could
control the flow of air in the
Figure 9: Examples of lattice arrangements.
Figure 10: Mashrabiya from a house in Cairo
Figure 11: Mashrabiya of the Jaml-Ad-Dhahabi hiuse, Cairo, showing
increased interstitial spacing at high lev- els.
International Workshop on Energy Performance and Environmental 5
Quality of Buildings, July 2006, Milos island, Greece
interior with interior elements which were placed behind the
opening.
According to the Equation of Continuity, the flow of air through
claustra is realized in a fast way because of the small
intersection of the gap. So in the interior, the air enters in a
small quan- tity but with high velocity.
Another construction in which small open- ings have been
encountered, are the houses for pigeons in the Cycladic islands. In
these con- structions the protection from the high speed winds is
needed, as long as the users are pi- geons. For that reason, the
orientation of the openings, the construction of special
protective
walls and the internal organisation of the pigeon house contribute
to the shaping of the ideal con- ditions of comfort for the
pigeons.
7. CONCLUSIONS This paper has been based on a graduation re- search
conducted at the University of Patras in Greece, under the
supervision of Dr. K.A. Liapi. The research on historical
prototypes has lead to an organization and a presentation of these
his- torical prototypes and some contemporary ap- plications. Their
construction was the result of the experience and the studying of
the character- istics of air by the people at each region.
It needs to be mentioned that the research has shown that air
cooling practices have been proved very efficient particularly when
com- bined. Obviously, such practices were based on the climatic
conditions of the region, local con- struction methods and the way
of living of the inhabitants etc.
Furthermore, responding to the question whether the contemporary
applications consti- tute an evolution of historical practices or
if they are entirely new, it can be stated that what is more
important is that the historical proto- types combined with recent
technological ad- vancements can lead to a more natural and envi-
ronmental-friendly architectural design.
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Figure 12: Double skin façade with ventilation flaps ex-
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Figure 13: Claustra in a parapet wall on the roof of a building in
Oman.
Figure 14: Feggites over doors in buildings in the Cy- cladic
Islands.
Figure 15: Pigeon house in Tinos.
6 International Workshop on Energy Performance and Environmental
Quality of Buildings, July 2006, Milos island, Greece
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