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Climate and urban planning: The example of the planning code for Vicente Lopez, Buenos Aires
Energy and Buildings, 15.16 (1990/91) 35 - 41
35
Climate and Urban Planning: The Example of the Planning Code for Vicente Lopez, Buenos Aires JOHN MARTIN EVANS and SILVIA de SCHILLER Research Programme "Habitat and Energy", Faculty of Architecture, Design and Urban Planning, University of Buenos Aires, Pabellon 3, Piso 4, Cuidad Universitaria, (1428) Federal Capital, Buenos Aires (Argentina)
ABSTRACT
This paper analyses the existing urban development, the economic context, the legal framework and the climatic requirements that shaped the proposals for the Revised Planning Code of the Municipality of Vicente Lopez in the Greater Buenos Aires Metropolitan Area. Due to the extensive existing urban development, land sub-division and strong real-estate pressures, there are limited opportunities for urban planning decisions which respond to climatic requirements. However, the climate-conscious planning and design measures described in this paper were incorporated in the new code in order to promote better microclimatic and environmental conditions.
INTRODUCTION The Ur b an District of Vicente Lopez, in Buenos Aires Province, was established in 1902 to the north-west of the Federal Capital of Argentina. The District now has a population of approximately 350 000 inhabitants and is situated in the inner ring of the G r e a t e r Buenos Aires Metropolitan Area (total population 10 million). The area of the district shown in Fig. 1 is 37 km 2 with a coastline of 5 km on the River Plate and a maximum distance of 8 km from the coast. In 1987, the municipal authorities appointed a planning team, directed by the authors of this paper, to r e s t r u c t u r e and update the existing Planning Code [1] and establish new zoning provisions. In a previous study [2], the authors developed planning and design recommendations based on environmental and climatic criteria for a projected new city. One of the aims of the study for the new code was to test if similar objectives 0378-7788/91/$3.50
i REGION 7
"t0
Fig. 1. Location of Vicente Lopez and the 10 meteorological stations in the Greater Buenos Aires Metropolitan Region.
could be applied in an urban area where existing development would limit large-scale or comprehensive interventions. In existing built-up areas, climate-conscious planning implies a careful analysis, conserving the features of the urban tissue which produce favourable urban microclimates while avoiding those aspects t h a t lead to a deterioration of environmental conditions. T h r o u g h a series of controls and measures to promote desirable building forms, development can be guided to achieve a better urban microclimate. • This paper indicates the existing conditions and the requirements for future urban design, with special emphasis on the climatic aspects, which were considered while developing the revised Planning Code. This is followed by an analysis of the existing planning and urban development context, the political and legal framework, the real-estate pressures and the participation of professionals and other interested parties in the development of the Code. Finally, features of the proposal and an evaluation of the possibilities to incorporate climate-conscious design and planning mea~ Elsevier Sequoia/Printed in The Netherlands
36
sures in existing urban tissues complete this presentation.
CLIMATE AND URBAN DESIGN REQUIREMENTS
Climate Buenos Aires is situated in the warm temperate zone of Argentina with a latitude of 3 4 S. The main features of the climate are summarized in Table 1. The winters are mild with very occasional frosts due to the low latitude, the urban microclimate and the moderating influence of the River Plate Estuary, which is over 30 km wide in the sector in front of the city. The summers are warm and oppressive with considerable humidity that makes ventilation desirable. On calm hot evenings, an onshore breeze brings welcome relief. The rainfall is plentiful and well distributed throughout the year, with occasional intense storms. The cloud cover is variable with successions of cloudy and clear days in each month, and with an increasing tendency to cloudiness in winter. Occasional very heavy rains have caused widespread flooding and damage. A total of 295.4 mm fell on May 31, 1985, forcing 95 000 people to evacuate their homes, flooding suburban and underground railways and affecting over 15% of the city's electricity supply. Urban development in Vicente Lopez and neighbouring municipalities has accentuated this problem as the rainfall sewer outlet~ i the Federal Capital, built in the 1930s, do n~ provide sufficient capacity for rapid drainage of surface water.
Urban microclimate The National Meteorological Service p u b lishes climate data for 10 stations in the Greater Buenos Aires Metropolitan Region. The four stations whose location is shown in Fig. 1 are considered to indicate the typical variations of urban microclimate in a section perpendicular to the river. It should be noted that the Central Observatory is situated in a park surrounded by development that has a somewhat higher density than that found in Vicente Lopez. An analysis of the data of the four stations is presented in Table 2, which shows the following tendencies: - - h i g h e r average temperatures in the city centre in summer and winter; --lower maximum summer temperatures near the River Plate; --lower temperature swings on the River Plate coast; - - h i g h e r minimum winter temperatures in areas closer to the coast. Figure 2 shows a schematic section of the urban district perpendicular to the river with the approximate distances of the meteorological stations, the ground profile and the location of the principal avenues mentioned in the following text.
Urban design recommendations The following recommendations for urban development in the Vicente Lopez Municipality are the result of climatic analyses: --avoid continuous barriers of high-rise buildings that block on-shore and off-shore breezes; --limit maximum ground coverage by build-
TABLE l Summary of the meteorological data for Buenos Aires* Data
Summer
Winter
Absolute max. temperature (:C) Average max. temperature ( C ) Average temperature ( C ) Average min. temperature ( C ) Absolute min. temperature ( C ) Average relative humidity (%) Rainfall (mm) Wind speed (km/h) Cloud cover (oktars)
37.8 29.4 24.3 19.5 t0.1 63 144 13 3.5
25.4 15.7 11.3 7.7 -1.6 78 72 10 4.5
* Central Observatory, Buenos Aires [3].
Annual
22.5 17.5 13,3 71 1143 11 3.8
37 TABLE 2 Urban microclimate variation in Greater Buenos Aires* Parameters
Number (Fig. 1) and locality of stations
Distance from the River Plate (km) Winter temperature ( C ) Average max. Average Average min. Average daily range Absolute min. (1961-70) Absolute min. (1971 - 80) Summer temperature ("C) Absolute max. Average max. Average Average min. Range Annual averages Relative humidity (%) Hours of sunshine Rainfall (mm) Wind speed (km/h)
1
2
5
4
Aeroparque
Observatory
E1 Palomar
Castellar
0.2
5
18
21
14.9 11.2 8.5 6.4 -4.8 0.0
15.7 11.3 7.7 8.0 -5.2 - 1.6
15.4 10.5 6.4 9.0 -8.0 - 4.0
15.7 10.4 6.3 9.4 -8.0 - 4.4
37.3 28.5 24.1 20.2 8.3
37.2 29.9 24.3 19.0 10.9
37.4 29.7 24.0 18.0 11.7
40.3 29.5 23.7 17.8 11.7
73 3.8 1062 16
71 3.8 1143 11
72 3.6 1003 13
70 4.0 1001 9
* Sources of data are refs. 3 and 4.
3O
Averaqe daily t ~ r a l u r e
l
Highway
swing
o River
Avenue Maipu ivb~u~e~--~
Fig. 2. Schematic section of the Urban District showing climatic variations and urban profile.
ings and pavement in order to create absorbent surfaces to reduce rainfall run-off; --allow spaces between buildings to ensure adequate levels of natural light and ventilation; --control building heights, according to the space between buildings, to allow the penetra-
tion of winter sunlight in neighbouring buildings; --avoid building forms that produce an acceleration of wind and turbulence at pedestrian level; --limit building densities to control the " h e a t island effect" which is especially undesirable in summer.
EXISTING PLANNING AND URBAN DEVELOPMENT
The existing urban development maintains the initial subdivisions carried out at the turn of this century, based on a city block of approximately 100 m x 100 m and a plot with a minimum frontage of 8.66 m or 10 m and varying depths. The first areas to be developed, in the vicinity of the railway stations, have many detached houses in plots of double the minimum width. These residential areas have a high quality environment with extensive planting. Later developments, with smaller blocks (100 m x 50 m) and plots, have higher densities
38
17
0*
DOO ~ C ~ 3 D DO OD DO O~O~i3 D O E] D O C O OO£]DODODOD
~ooooooooo'g
~z~OO0 DO O 0 0 0
River Plate
]n0~)~0[
]00E]l~[
,
i
Fede ra l Capital
r
Fig. 3. The Urban District of Vicente Lopez with the main avenues and areas zoned for high-rise building (black). and limited planting. In the peripheral and low-lying areas, used for mixed residential and industrial development, ground coverage is very high. It often reaches 100% with factories in the deeper plots located in the middle of each block and houses in the smaller plots occupying the corners of the blocks. Along the main roads, which run parallel to the coast (Libertador and Maipu Avenues), high-rise building has been permitted, though the urban profile is ragged and incomplete. The main real-estate pressures and political discussions concern these road frontages (Fig. 3). The municipality lacks the required economic resources needed to intervene in the unification or rationalization of existing subdivisions and guide comprehensive urban redevelopment. The legislative powers for municipal initiatives are available but limited and seldom used. The Planning Code is therefore an important tool to channel private developments.
REAL.ESTATE PRESSURES The high-density development permitted in the 1960s and 70s raised land values in the main avenues. Meanwhile, the provincial planning legislation and the present code which now limit excessive plot ratios have effectively paralysed further building on these frontages during the last decade. There is considerable pressure to allow further high-rise buildings, both from the real-estate sector and representatives of professional bodies. From the point of view of urban design, completion of the ragged urban profile would be desirable. This can only be achieved if maximum densities are increased. However, it is essential to control the permitted building forms to avoid the disadvantages of existing structures and the results of further similar development, namely: - - l a c k of winter sun in urban spaces; - - i n a d e q u a t e natural light in internal patios;
39 --poor ventilation and breeze in neighbouring areas; - - w i n d acceleration at pedestrian level; --ragged, unfinished urban profile with incomplete development. There remains a limited margin to increase building and population densities on these avenues, according to the provincial law. Technical studies and discussions with the interested parties were necessary to define suitable proposals that allow a density increase while safeguarding environmental and urban design requirements.
PARTICIPATION IN THE PLANNINGPROCESS The revision and improvement of the Planning Code must be broadly acceptable for those investing in new buildings and the modification of existing ones, as well as the professionals responsible for proposing new designs to clients, submitting documentation for planning permission and supervising the construction. To achieve this objective, the municipal authorities convened an advisory committee formed with representatives of professional organizations such as estate agents, surveyors, architects, engineers, etc. The planning team and municipal authorities were also represented on this committee. In a regular series of meetings, potential conflicts were discussed and the representatives attempted to achieve a consensus.
INNOVATIONS IN THE NEW PLAN As a result of the technical planning studies on one side, and the discussions in the
committee meetings on the other, the following results were achieved: --avoidance of a continuous barrier of highrise buildings on the two avenues parallel to the coast, in order to improve ventilation of neighbouring areas; --encouragement of relatively high tower buildings on continuous low podiums, to avoid high wind velocities at pedestrian level; --prohibition of the use of enclosed patios to illuminate and ventilate habitable rooms in high-rise blocks; --limitation of building heights in residential areas to ensure adequate winter sun in neighbouring plots; ~ e f i n i t i o n of minimum absorbent surfaces for the rain-water soak-away in all plots; the only exceptions are limited commercial areas where plot coverage is already complete; --increase of maximum building height in large low-rise buildings, providing t h a t no additional blocking of winter sun occurs in neighbouring plots.
High-rise buildings The maximum densities allowed under the existing and proposed Planning Code are shown in Table 3. These increases have been achieved while safeguarding and improving the resulting environmental conditions. Figure 4 shows the building forms permitted under the existing and proposed code, together with the corresponding environmental advantages and disadvantages. During the last 20 years, certain zones have been defined, close to existing railway stations, where high-rise buildings were permitted. In many of these zones, no high-rise buildings have been constructed due to lack of suitable larger plots and insufficient demand.
TABLE 3 Existing and proposed maximumbuilding densities Densities
Existing Code
Proposed Code
Max. ground coverage Building/plot ratio
0.6 2.5
Population density (persons/ha) Building height (metres) (floors)
575
0.6 2.5 (residential) 2.8 (mixed) 1000 (residential) 1140 (mixed) 33.5 11
30 10
40
Zone R1
J
Zone C4 .L
Fig. 5. Control of spaces between buildings to ensure adequate winter sun, natural daylight and ventilation. (a) Typical street sections. (b) Simplified application of the solar envelope concept, used for large isolated buildings.
tres. T h e p r o j e c t i o n of b a l c o n i e s is also limited to e n s u r e a d e q u a t e levels of n a t u r a l daylight and v e n t i l a t i o n .
f, J
Fig. 4. High-rise building forms permitted under the existing Code and the new proposals. (a) The existing Code: --exposed party walls; inadequate ventilation and light in patios; --wind acceleration at low level; --incentives for set-backs; --lack of ventilation in adjacent areas. (b) The new proposals: all rooms open on to external spaces; --wind acceleration at podium level; partial sun and improved daylight in streets; --ventilation of adjacent areas; integration of existing buildings.
This w a s f o r t u n a t e as e x i s t i n g u r b a n services are limited a n d s t r e e t widths are i n a d e q u a t e . T h e s e a r e a s for high-rise buildings h a v e b e e n re-zoned for l o w e r d e v e l o p m e n t in the new proposals. The e x i s t i n g Code allows the c o n s t r u c t i o n of two high-rise blocks in a n a r r o w plot of up to 50 m d e p t h in h i g h - d e n s i t y areas. In the p r o p o s e d Code, b l o c k h e i g h t is limited to four s t o r e y s in this case and the p a t i o b e t w e e n buildings h a s a m i n i m u m w i d t h of e i g h t me-
Solar envelope T h e c o n c e p t of the s o l a r e n v e l o p e i n v o l v e s a series of l i m i t i n g p l a n e s to c o n t r o l building height, e n s u r i n g u n o b s t r u c t e d s u n l i g h t in n e i g h b o u r i n g plots. T h e slope of the planes d e p e n d s on the latitude, t i m e of y e a r c h o s e n and n u m b e r of h o u r s of u n o b s t r u c t e d s u n l i g h t [5]. In the case of the design r e c o m m e n d a t i o n s for a new city [2], it was possible to a p p l y the c o n c e p t of the s o l a r e n v e l o p e a n d o b t a i n acc e p t a b l e building densities. T h e existing Plann i n g Code a n d e s t a b l i s h e d u r b a n d e v e l o p m e n t w i t h i n the M u n i c i p a l i t y of V i c e n t e Lopez, does not f a v o u r the d i r e c t i n c o r p o r a t i o n of the concept. H o w e v e r , it was possible to c o n t r o l building h e i g h t s in r e l a t i o n to s t r e e t widths, u s i n g the limiting p l a n e s of the s o l a r e n v e l o p e (Fig. 5(a)). A simplification of the s o l a r e n v e l o p e concept w a s also applied to l a r g e isolated buildings w i t h o u t p a r t y walls, w h e r e a n a d d i t i o n a l 0.50 m is allowed for e a c h a d d i t i o n a l m e t r e from the site b o u n d a r i e s , as s h o w n in Fig. 5(b). This inclined p l a n e p r e v e n t s a n y addit i o n a l o b s t r u c t i o n of w i n t e r sun in the neighb o u r i n g plots f r o m 09:00 to 15:00.
CONCLUSIONS T h e e x i s t i n g P l a n n i n g Code does n o t include p r e c i s e l y defined m e a s u r e s to e n s u r e a d e q u a t e e n v i r o n m e n t a l s t a n d a r d s , to t a k e adv a n t a g e of t h e f a v o u r a b l e aspects of the u r b a n
41
microclimate or to avoid the impact of undesirable climatic variables. The subdivision and existing buildings also severely limit the possibilities for future development in this built-up area. The characteristics of the subdivisions play an important part in the definition of the environmental quality and the potential for future building. Despite this situation, the studies carried out show that it is still possible to improve the quality of the urban microclimate through measures which control building form. To encourage new building with these desirable urban and climatic features, increased densities are allowed, providing an economic incentive. New proposals must be discussed with representatives of the interested parties to ensure acceptable proposals which will be implemented in practice. However, negotiations will be hard. The planner must have clear objectives and the technical knowledge required to evaluate alternative proposals and their environmental consequences and microclimatic impact.
ACKNOWLEDGEMENTS
The authors wish to acknowledge the contributions of the planning team: Marta Stolkiner, Maria Cristina Fraguglia, Nilda Pierro, Adriana Perez Anaclerio, Marcelo Molinatti and Analia Fernandez, and the support received from the Council and Authorities of the Municipality of Vicente Lopez.
REFERENCES
1 Codigo de Ordenamiento Urbano (Urban Planning Code), Municipalidad de Vicente Lopez, Buenos Aires, 1984. 2 S. de Schiller and J. M. Evans, Healthy buildings for a new city: bioclimatic design guide for Argentina's new capital, Planning, Physics and Climate Technology for Healthier Buildings, Proc. Healthy Buildings '88, Vol. 2, Swedish Council for Building Research, Stockholm, 1988. 3 Estadisticas Meteorol6gicas 1971-1980 (Meteorological Statistics 1971 - 1980), Servicio Meteorol6gico Nacional, Buenos Aires, 1986. 4 Estadistica Climatol6gica 1961. 1970 (Climatic Statistics 1961. 1970), Servicio Meteorol6gico Nacional, Buenos Aires, 1981. 5 Ralph L. Knowles, Sun Rhythm Form, The M.I.T. Press, Cambridge, MA, 1981.
35
Climate and Urban Planning: The Example of the Planning Code for Vicente Lopez, Buenos Aires JOHN MARTIN EVANS and SILVIA de SCHILLER Research Programme "Habitat and Energy", Faculty of Architecture, Design and Urban Planning, University of Buenos Aires, Pabellon 3, Piso 4, Cuidad Universitaria, (1428) Federal Capital, Buenos Aires (Argentina)
ABSTRACT
This paper analyses the existing urban development, the economic context, the legal framework and the climatic requirements that shaped the proposals for the Revised Planning Code of the Municipality of Vicente Lopez in the Greater Buenos Aires Metropolitan Area. Due to the extensive existing urban development, land sub-division and strong real-estate pressures, there are limited opportunities for urban planning decisions which respond to climatic requirements. However, the climate-conscious planning and design measures described in this paper were incorporated in the new code in order to promote better microclimatic and environmental conditions.
INTRODUCTION The Ur b an District of Vicente Lopez, in Buenos Aires Province, was established in 1902 to the north-west of the Federal Capital of Argentina. The District now has a population of approximately 350 000 inhabitants and is situated in the inner ring of the G r e a t e r Buenos Aires Metropolitan Area (total population 10 million). The area of the district shown in Fig. 1 is 37 km 2 with a coastline of 5 km on the River Plate and a maximum distance of 8 km from the coast. In 1987, the municipal authorities appointed a planning team, directed by the authors of this paper, to r e s t r u c t u r e and update the existing Planning Code [1] and establish new zoning provisions. In a previous study [2], the authors developed planning and design recommendations based on environmental and climatic criteria for a projected new city. One of the aims of the study for the new code was to test if similar objectives 0378-7788/91/$3.50
i REGION 7
"t0
Fig. 1. Location of Vicente Lopez and the 10 meteorological stations in the Greater Buenos Aires Metropolitan Region.
could be applied in an urban area where existing development would limit large-scale or comprehensive interventions. In existing built-up areas, climate-conscious planning implies a careful analysis, conserving the features of the urban tissue which produce favourable urban microclimates while avoiding those aspects t h a t lead to a deterioration of environmental conditions. T h r o u g h a series of controls and measures to promote desirable building forms, development can be guided to achieve a better urban microclimate. • This paper indicates the existing conditions and the requirements for future urban design, with special emphasis on the climatic aspects, which were considered while developing the revised Planning Code. This is followed by an analysis of the existing planning and urban development context, the political and legal framework, the real-estate pressures and the participation of professionals and other interested parties in the development of the Code. Finally, features of the proposal and an evaluation of the possibilities to incorporate climate-conscious design and planning mea~ Elsevier Sequoia/Printed in The Netherlands
36
sures in existing urban tissues complete this presentation.
CLIMATE AND URBAN DESIGN REQUIREMENTS
Climate Buenos Aires is situated in the warm temperate zone of Argentina with a latitude of 3 4 S. The main features of the climate are summarized in Table 1. The winters are mild with very occasional frosts due to the low latitude, the urban microclimate and the moderating influence of the River Plate Estuary, which is over 30 km wide in the sector in front of the city. The summers are warm and oppressive with considerable humidity that makes ventilation desirable. On calm hot evenings, an onshore breeze brings welcome relief. The rainfall is plentiful and well distributed throughout the year, with occasional intense storms. The cloud cover is variable with successions of cloudy and clear days in each month, and with an increasing tendency to cloudiness in winter. Occasional very heavy rains have caused widespread flooding and damage. A total of 295.4 mm fell on May 31, 1985, forcing 95 000 people to evacuate their homes, flooding suburban and underground railways and affecting over 15% of the city's electricity supply. Urban development in Vicente Lopez and neighbouring municipalities has accentuated this problem as the rainfall sewer outlet~ i the Federal Capital, built in the 1930s, do n~ provide sufficient capacity for rapid drainage of surface water.
Urban microclimate The National Meteorological Service p u b lishes climate data for 10 stations in the Greater Buenos Aires Metropolitan Region. The four stations whose location is shown in Fig. 1 are considered to indicate the typical variations of urban microclimate in a section perpendicular to the river. It should be noted that the Central Observatory is situated in a park surrounded by development that has a somewhat higher density than that found in Vicente Lopez. An analysis of the data of the four stations is presented in Table 2, which shows the following tendencies: - - h i g h e r average temperatures in the city centre in summer and winter; --lower maximum summer temperatures near the River Plate; --lower temperature swings on the River Plate coast; - - h i g h e r minimum winter temperatures in areas closer to the coast. Figure 2 shows a schematic section of the urban district perpendicular to the river with the approximate distances of the meteorological stations, the ground profile and the location of the principal avenues mentioned in the following text.
Urban design recommendations The following recommendations for urban development in the Vicente Lopez Municipality are the result of climatic analyses: --avoid continuous barriers of high-rise buildings that block on-shore and off-shore breezes; --limit maximum ground coverage by build-
TABLE l Summary of the meteorological data for Buenos Aires* Data
Summer
Winter
Absolute max. temperature (:C) Average max. temperature ( C ) Average temperature ( C ) Average min. temperature ( C ) Absolute min. temperature ( C ) Average relative humidity (%) Rainfall (mm) Wind speed (km/h) Cloud cover (oktars)
37.8 29.4 24.3 19.5 t0.1 63 144 13 3.5
25.4 15.7 11.3 7.7 -1.6 78 72 10 4.5
* Central Observatory, Buenos Aires [3].
Annual
22.5 17.5 13,3 71 1143 11 3.8
37 TABLE 2 Urban microclimate variation in Greater Buenos Aires* Parameters
Number (Fig. 1) and locality of stations
Distance from the River Plate (km) Winter temperature ( C ) Average max. Average Average min. Average daily range Absolute min. (1961-70) Absolute min. (1971 - 80) Summer temperature ("C) Absolute max. Average max. Average Average min. Range Annual averages Relative humidity (%) Hours of sunshine Rainfall (mm) Wind speed (km/h)
1
2
5
4
Aeroparque
Observatory
E1 Palomar
Castellar
0.2
5
18
21
14.9 11.2 8.5 6.4 -4.8 0.0
15.7 11.3 7.7 8.0 -5.2 - 1.6
15.4 10.5 6.4 9.0 -8.0 - 4.0
15.7 10.4 6.3 9.4 -8.0 - 4.4
37.3 28.5 24.1 20.2 8.3
37.2 29.9 24.3 19.0 10.9
37.4 29.7 24.0 18.0 11.7
40.3 29.5 23.7 17.8 11.7
73 3.8 1062 16
71 3.8 1143 11
72 3.6 1003 13
70 4.0 1001 9
* Sources of data are refs. 3 and 4.
3O
Averaqe daily t ~ r a l u r e
l
Highway
swing
o River
Avenue Maipu ivb~u~e~--~
Fig. 2. Schematic section of the Urban District showing climatic variations and urban profile.
ings and pavement in order to create absorbent surfaces to reduce rainfall run-off; --allow spaces between buildings to ensure adequate levels of natural light and ventilation; --control building heights, according to the space between buildings, to allow the penetra-
tion of winter sunlight in neighbouring buildings; --avoid building forms that produce an acceleration of wind and turbulence at pedestrian level; --limit building densities to control the " h e a t island effect" which is especially undesirable in summer.
EXISTING PLANNING AND URBAN DEVELOPMENT
The existing urban development maintains the initial subdivisions carried out at the turn of this century, based on a city block of approximately 100 m x 100 m and a plot with a minimum frontage of 8.66 m or 10 m and varying depths. The first areas to be developed, in the vicinity of the railway stations, have many detached houses in plots of double the minimum width. These residential areas have a high quality environment with extensive planting. Later developments, with smaller blocks (100 m x 50 m) and plots, have higher densities
38
17
0*
DOO ~ C ~ 3 D DO OD DO O~O~i3 D O E] D O C O OO£]DODODOD
~ooooooooo'g
~z~OO0 DO O 0 0 0
River Plate
]n0~)~0[
]00E]l~[
,
i
Fede ra l Capital
r
Fig. 3. The Urban District of Vicente Lopez with the main avenues and areas zoned for high-rise building (black). and limited planting. In the peripheral and low-lying areas, used for mixed residential and industrial development, ground coverage is very high. It often reaches 100% with factories in the deeper plots located in the middle of each block and houses in the smaller plots occupying the corners of the blocks. Along the main roads, which run parallel to the coast (Libertador and Maipu Avenues), high-rise building has been permitted, though the urban profile is ragged and incomplete. The main real-estate pressures and political discussions concern these road frontages (Fig. 3). The municipality lacks the required economic resources needed to intervene in the unification or rationalization of existing subdivisions and guide comprehensive urban redevelopment. The legislative powers for municipal initiatives are available but limited and seldom used. The Planning Code is therefore an important tool to channel private developments.
REAL.ESTATE PRESSURES The high-density development permitted in the 1960s and 70s raised land values in the main avenues. Meanwhile, the provincial planning legislation and the present code which now limit excessive plot ratios have effectively paralysed further building on these frontages during the last decade. There is considerable pressure to allow further high-rise buildings, both from the real-estate sector and representatives of professional bodies. From the point of view of urban design, completion of the ragged urban profile would be desirable. This can only be achieved if maximum densities are increased. However, it is essential to control the permitted building forms to avoid the disadvantages of existing structures and the results of further similar development, namely: - - l a c k of winter sun in urban spaces; - - i n a d e q u a t e natural light in internal patios;
39 --poor ventilation and breeze in neighbouring areas; - - w i n d acceleration at pedestrian level; --ragged, unfinished urban profile with incomplete development. There remains a limited margin to increase building and population densities on these avenues, according to the provincial law. Technical studies and discussions with the interested parties were necessary to define suitable proposals that allow a density increase while safeguarding environmental and urban design requirements.
PARTICIPATION IN THE PLANNINGPROCESS The revision and improvement of the Planning Code must be broadly acceptable for those investing in new buildings and the modification of existing ones, as well as the professionals responsible for proposing new designs to clients, submitting documentation for planning permission and supervising the construction. To achieve this objective, the municipal authorities convened an advisory committee formed with representatives of professional organizations such as estate agents, surveyors, architects, engineers, etc. The planning team and municipal authorities were also represented on this committee. In a regular series of meetings, potential conflicts were discussed and the representatives attempted to achieve a consensus.
INNOVATIONS IN THE NEW PLAN As a result of the technical planning studies on one side, and the discussions in the
committee meetings on the other, the following results were achieved: --avoidance of a continuous barrier of highrise buildings on the two avenues parallel to the coast, in order to improve ventilation of neighbouring areas; --encouragement of relatively high tower buildings on continuous low podiums, to avoid high wind velocities at pedestrian level; --prohibition of the use of enclosed patios to illuminate and ventilate habitable rooms in high-rise blocks; --limitation of building heights in residential areas to ensure adequate winter sun in neighbouring plots; ~ e f i n i t i o n of minimum absorbent surfaces for the rain-water soak-away in all plots; the only exceptions are limited commercial areas where plot coverage is already complete; --increase of maximum building height in large low-rise buildings, providing t h a t no additional blocking of winter sun occurs in neighbouring plots.
High-rise buildings The maximum densities allowed under the existing and proposed Planning Code are shown in Table 3. These increases have been achieved while safeguarding and improving the resulting environmental conditions. Figure 4 shows the building forms permitted under the existing and proposed code, together with the corresponding environmental advantages and disadvantages. During the last 20 years, certain zones have been defined, close to existing railway stations, where high-rise buildings were permitted. In many of these zones, no high-rise buildings have been constructed due to lack of suitable larger plots and insufficient demand.
TABLE 3 Existing and proposed maximumbuilding densities Densities
Existing Code
Proposed Code
Max. ground coverage Building/plot ratio
0.6 2.5
Population density (persons/ha) Building height (metres) (floors)
575
0.6 2.5 (residential) 2.8 (mixed) 1000 (residential) 1140 (mixed) 33.5 11
30 10
40
Zone R1
J
Zone C4 .L
Fig. 5. Control of spaces between buildings to ensure adequate winter sun, natural daylight and ventilation. (a) Typical street sections. (b) Simplified application of the solar envelope concept, used for large isolated buildings.
tres. T h e p r o j e c t i o n of b a l c o n i e s is also limited to e n s u r e a d e q u a t e levels of n a t u r a l daylight and v e n t i l a t i o n .
f, J
Fig. 4. High-rise building forms permitted under the existing Code and the new proposals. (a) The existing Code: --exposed party walls; inadequate ventilation and light in patios; --wind acceleration at low level; --incentives for set-backs; --lack of ventilation in adjacent areas. (b) The new proposals: all rooms open on to external spaces; --wind acceleration at podium level; partial sun and improved daylight in streets; --ventilation of adjacent areas; integration of existing buildings.
This w a s f o r t u n a t e as e x i s t i n g u r b a n services are limited a n d s t r e e t widths are i n a d e q u a t e . T h e s e a r e a s for high-rise buildings h a v e b e e n re-zoned for l o w e r d e v e l o p m e n t in the new proposals. The e x i s t i n g Code allows the c o n s t r u c t i o n of two high-rise blocks in a n a r r o w plot of up to 50 m d e p t h in h i g h - d e n s i t y areas. In the p r o p o s e d Code, b l o c k h e i g h t is limited to four s t o r e y s in this case and the p a t i o b e t w e e n buildings h a s a m i n i m u m w i d t h of e i g h t me-
Solar envelope T h e c o n c e p t of the s o l a r e n v e l o p e i n v o l v e s a series of l i m i t i n g p l a n e s to c o n t r o l building height, e n s u r i n g u n o b s t r u c t e d s u n l i g h t in n e i g h b o u r i n g plots. T h e slope of the planes d e p e n d s on the latitude, t i m e of y e a r c h o s e n and n u m b e r of h o u r s of u n o b s t r u c t e d s u n l i g h t [5]. In the case of the design r e c o m m e n d a t i o n s for a new city [2], it was possible to a p p l y the c o n c e p t of the s o l a r e n v e l o p e a n d o b t a i n acc e p t a b l e building densities. T h e existing Plann i n g Code a n d e s t a b l i s h e d u r b a n d e v e l o p m e n t w i t h i n the M u n i c i p a l i t y of V i c e n t e Lopez, does not f a v o u r the d i r e c t i n c o r p o r a t i o n of the concept. H o w e v e r , it was possible to c o n t r o l building h e i g h t s in r e l a t i o n to s t r e e t widths, u s i n g the limiting p l a n e s of the s o l a r e n v e l o p e (Fig. 5(a)). A simplification of the s o l a r e n v e l o p e concept w a s also applied to l a r g e isolated buildings w i t h o u t p a r t y walls, w h e r e a n a d d i t i o n a l 0.50 m is allowed for e a c h a d d i t i o n a l m e t r e from the site b o u n d a r i e s , as s h o w n in Fig. 5(b). This inclined p l a n e p r e v e n t s a n y addit i o n a l o b s t r u c t i o n of w i n t e r sun in the neighb o u r i n g plots f r o m 09:00 to 15:00.
CONCLUSIONS T h e e x i s t i n g P l a n n i n g Code does n o t include p r e c i s e l y defined m e a s u r e s to e n s u r e a d e q u a t e e n v i r o n m e n t a l s t a n d a r d s , to t a k e adv a n t a g e of t h e f a v o u r a b l e aspects of the u r b a n
41
microclimate or to avoid the impact of undesirable climatic variables. The subdivision and existing buildings also severely limit the possibilities for future development in this built-up area. The characteristics of the subdivisions play an important part in the definition of the environmental quality and the potential for future building. Despite this situation, the studies carried out show that it is still possible to improve the quality of the urban microclimate through measures which control building form. To encourage new building with these desirable urban and climatic features, increased densities are allowed, providing an economic incentive. New proposals must be discussed with representatives of the interested parties to ensure acceptable proposals which will be implemented in practice. However, negotiations will be hard. The planner must have clear objectives and the technical knowledge required to evaluate alternative proposals and their environmental consequences and microclimatic impact.
ACKNOWLEDGEMENTS
The authors wish to acknowledge the contributions of the planning team: Marta Stolkiner, Maria Cristina Fraguglia, Nilda Pierro, Adriana Perez Anaclerio, Marcelo Molinatti and Analia Fernandez, and the support received from the Council and Authorities of the Municipality of Vicente Lopez.
REFERENCES
1 Codigo de Ordenamiento Urbano (Urban Planning Code), Municipalidad de Vicente Lopez, Buenos Aires, 1984. 2 S. de Schiller and J. M. Evans, Healthy buildings for a new city: bioclimatic design guide for Argentina's new capital, Planning, Physics and Climate Technology for Healthier Buildings, Proc. Healthy Buildings '88, Vol. 2, Swedish Council for Building Research, Stockholm, 1988. 3 Estadisticas Meteorol6gicas 1971-1980 (Meteorological Statistics 1971 - 1980), Servicio Meteorol6gico Nacional, Buenos Aires, 1986. 4 Estadistica Climatol6gica 1961. 1970 (Climatic Statistics 1961. 1970), Servicio Meteorol6gico Nacional, Buenos Aires, 1981. 5 Ralph L. Knowles, Sun Rhythm Form, The M.I.T. Press, Cambridge, MA, 1981.