air moving in and through building: historical prototypes
TRANSCRIPT
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.
REFERENCES Brown, G.Z. and M. Dekay, 2001. Sun, Wind & Light,
Figure 12: Double skin façade with ventilation flaps ex- ternally.
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
Architectural design strategies, John Wiley & Sons, Inc.
Melaragno, G.M. Wind in Architectural and Environ- mental Design, Van Nostrand Reinhold Company.
Steele, J., 1988. Hassan Fathy, Architectural Monographs, London: Academy Editions-St. Martin’s Press
Hassan, F., 1986. Natural Energy and Vernacular Archi- tecture, Principles and examples with Reference to Hot Arid Climates, The University of Chicago Press.
Kaizer, T., 1984. Shelter in Saudi Arabia, New York: Academy editions/st. Martin’ s press.
Santamouris. M., 1998. Natural Ventilation in Build- ings/A design Handbook, Editor Francis Allard project coordinator Mat. Santamouris, London: James & James Ltd
Saymour, G.P., 1970. AIR CONDITIONING for building Engineers and Managers, operation and Maintenance by Seymour G Price, New York, Industrial Press Inc
Baruch, G., 1994. Passive and Low Energy Cooling Of Buildings, Van Nostrand Reinhold-An International Thomson Publishing Company.
Santamouris. M., 1998. Passive cooling of buildings edi- tors M. Santamouris, D. Asimakopoulos, London: James & James/European commission, directorate general xvii for energy.
United States department of Energy, 1980. Passive Cool- ing Handbook, Addenda, Sponsored and developed by U.S Department of Energy, Lawrence Berkeley Labo- ratory, the Passive cooling Working Group and the Florida Solar Energy Center.
Bower, J. 1995 Understanding Ventilation, How to de- sign, select, and install residential ventilation systems, The Healthy House Institute.
Fuller, M., Environmental Control Systems, heating cool- ing lighting-, McGraw-Hill International Edition.
Βασιλειδη, ., 1979. Οδοιπορα στις Μορφς και το φος του Ελληνικο Χρου, Γ κδοση Αθνα.
Ελληνικ Παραδοσιακ Αρχιτεκτονικ, Τνος, 1981. Εκδοτικς οκος «ΜΕΛΙΣΣΑ».
Ελληνικ Παραδοσιακ Αρχιτεκτονικ, Σφνος 1981, Εκδοτικς οκος «ΜΕΛΙΣΣΑ».
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.
REFERENCES Brown, G.Z. and M. Dekay, 2001. Sun, Wind & Light,
Figure 12: Double skin façade with ventilation flaps ex- ternally.
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
Architectural design strategies, John Wiley & Sons, Inc.
Melaragno, G.M. Wind in Architectural and Environ- mental Design, Van Nostrand Reinhold Company.
Steele, J., 1988. Hassan Fathy, Architectural Monographs, London: Academy Editions-St. Martin’s Press
Hassan, F., 1986. Natural Energy and Vernacular Archi- tecture, Principles and examples with Reference to Hot Arid Climates, The University of Chicago Press.
Kaizer, T., 1984. Shelter in Saudi Arabia, New York: Academy editions/st. Martin’ s press.
Santamouris. M., 1998. Natural Ventilation in Build- ings/A design Handbook, Editor Francis Allard project coordinator Mat. Santamouris, London: James & James Ltd
Saymour, G.P., 1970. AIR CONDITIONING for building Engineers and Managers, operation and Maintenance by Seymour G Price, New York, Industrial Press Inc
Baruch, G., 1994. Passive and Low Energy Cooling Of Buildings, Van Nostrand Reinhold-An International Thomson Publishing Company.
Santamouris. M., 1998. Passive cooling of buildings edi- tors M. Santamouris, D. Asimakopoulos, London: James & James/European commission, directorate general xvii for energy.
United States department of Energy, 1980. Passive Cool- ing Handbook, Addenda, Sponsored and developed by U.S Department of Energy, Lawrence Berkeley Labo- ratory, the Passive cooling Working Group and the Florida Solar Energy Center.
Bower, J. 1995 Understanding Ventilation, How to de- sign, select, and install residential ventilation systems, The Healthy House Institute.
Fuller, M., Environmental Control Systems, heating cool- ing lighting-, McGraw-Hill International Edition.
Βασιλειδη, ., 1979. Οδοιπορα στις Μορφς και το φος του Ελληνικο Χρου, Γ κδοση Αθνα.
Ελληνικ Παραδοσιακ Αρχιτεκτονικ, Τνος, 1981. Εκδοτικς οκος «ΜΕΛΙΣΣΑ».
Ελληνικ Παραδοσιακ Αρχιτεκτονικ, Σφνος 1981, Εκδοτικς οκος «ΜΕΛΙΣΣΑ».