sri lanka

Journal of Architectural and Planning Research 12:1 (Spring, 1995) 58

ENERGY-EFFICIENT URBAN DESIGN GUIDELINES FOR WARM-HUMID CITIES: STRATEGIES FOR COLOMBO,

SRI LANKA

Rohinton Emmanuel

INTRODUCTION

Energy consumptio world bank study rl consumption in 19~ to grow at least for

Although many fac that urbanization in income has resulte space conditioning ~

The pattern of enerj

in the warm-humid pact on the end COl healthier enviromne It is in this context wann-humid cities. the most efficient 0 space cooling.

The paper is in t, developed elsewber plications to a wan selected for this pu existing urban guidt

INFLUENCE OF 1

The patterns of ene: energy needs. A c( and a d~veloping cc consume a considen

This paper develops a set of energy-efficient urban design guidelines for an equatorial tropical city (Colombo, Sri Lanka), on the basis of a survey of energy-conserving urban design guidelines developed and applied principally in temperate regions. A total of twenty-two urban design guidelines currently enforced in various U.S. cities and six from the U.K are analyzed. These address one or more of the following urban energy requirements.o space-conditioning~ transportation and embodied energy needs. Problems related to excessive energy use in Colombo, Sri Lanka, are then identified by critically analyzing the "Colombo Development Plan n which legally binds all its urban development. Key factors analyzed are: floor area ratio, plot size, building height, open space, waterfront development, and landscaping. Finally, a hypothetical proposal is made for Colombo. It includes eight design guidelines (amendments to existing legislation as well as new) for the reduction of cooling needs and three for the reduction of transportation needs. These are presented within two broad policy options: prevention of parceling of urban land, use of existing railroad as a Mass Rapid Transportation system.

Copyright © 1995, Locke Science Publishing Company, Inco Chicago, IL, USA All Rights Reserved

Urban design has c ing/lighting. The d role to .play in urba strategies developed ing of new strategic and socioeconomic :

A literature survey mented was therefo regions. The maill American Planning regional, and state 1 identify communitie I


~INES

FOR

'~OLOMBO,

INTRODUCTION

.RILANKA

Energy consumption in the developing world has grown tremendously over the past years. A world bank study reports that the developing world which accounted for 20% of the total global consumption in 1970, increased its share to 33% in 1988 (Imran, 1990). This trend is expected to grow at least for the frrst three decades of the next century.

Emmanuel

Although many factors are cited as causes for the increase in consumption, it is generally agreed that urbanization in the region is the prime cause, particularly so in those areas where increasing income has resulted in greater demand for transportation and home appliances - especially space conditioning devices.

lton

~quatorial tropical .design guidelines two urban design analyzed. These oace-conditioning~ y use in Colombo, ment 1J [an" which 'a ratio, plot size, lly, a hypothetical (ments to existing r the reduction of ns: prevention of n system.

Jlishing Company, Inco All Rights Reserved

The pattern of energy consumption in moderate-income developing countries (most of which fall in the warm-humid belt) suggests that urban design related decisions can have a significant im pact on the end consumption of commercial energy. Such a reduction will inevitably lead to a healthier environment and ease the problem of pollution and congestion to a considerable degree. It is in this context that the present study formulates energy-efficient urban design guidelines for wami~humid cities. The hypothesis is that guidelines can be devised to conserve energy, and that the most efficient of them are related to two urban energy needs in the region: transportation and space cooling. The paper is in two parts: a survey of existing energy-conscious urban design guidelines developed elsewhere (primarily in the U.S.) in order to develop concepts; and hypothetical ap plications to a warm-humid city, so as to illustrate their applicability. Colombo, Sri Lanka, is selected for this purpose and strategies are formulated on the basis of a critical analysis of its existing urban guidelines that regulates the city form. INFLUENCE OF IJRBAN DESIGN ON URBAN ENERGY NEEDS

The patterns of energy use differs among nations, yet certain commonalities exist in their urban energy needs. A comparison of energy use patterns between a developed country like the U.S. and a d~veloping country like Sri Lanka shows that transportation and activities within buildings consume a considerable share of energy (Table 1). The magnitudes however are different. Urban design has an influence on energy needs for city transportation and space condition ing/lighting. The data in Table 1 can therefore be said to indicate that urban design has a vital role to .play in urban energy need reduction, irrespective of the socioeconomic context. Hence strategies developed in one climatic/economic context can be used to influence the conceptualiz ing of new strategies elsewhere. These of course need to be modified according to the climatic and socioeconomic needs of the different situations. A literature survey of the various energy efficient urban design strategies currently being imple mented was therefore made in the hope of deriving principles of application for warm, humid regions. The main source of information in this endeavor was a survey carried out by the American Planning Association (APA) in the fall of 1979. This survey covered over 1400 local, regional, and state planning agencies in the U.S., and involved an extensive literature review to identify communities that had adopted development regulations designed to save energy. Twen-


TABLE 1. Patterns of commercial energy consumption.

ACTIVITY

TABLE 2. Some

ENERGY CONSUMPTION (% of total country needs) U.S. U.K Sri Lanka

Industries

41.2

32.0

9.9

Transportation

21.0

18.0

16.4

Building Energy Needs

28.0

48.0

67.0

7.7

2.0

6.7

Agriculture/Others

Source: Erley & Mossena, 1980; Gardener, 1984 (quoted by Matthews, 1987); Amerasinghe, 1989.

ty-two separate examples enacted by thirteen cities and communities in the U.S. were identified (Erley and Mossena, 1980).

Reduction of Cooling Energy Needs One of the severe problems with the urban energy consumption lies with the very fonn of the city. Development, which is usually piece-meal, is left to grow in a haphazard manner and there are no overall fonn determinants for most cities. An energy-conscious city form will help direct individual buildings and sites to be properly oriented, shaded or exposed as the need be, ensure ventilation, etc. Ralph Knowles' (1974) conceptual fonn for Owen's valley in California is an example of such an attempt Although no examples for an energy-conscious city fonn for the warm-humid region was found, some small scale strategies towards this end do exist. For example, a total of eleven examples were found by the previously mentioned study specifically related to the reduction of space conditioning needs. They relate to one of the following urban design issues: • Orientation (site & building layout)

e Zoning

• External shading

• - Landscaping requirements.

Table 2 gives a description and the date of adoption of nine of these regulations enacted by seven communities. (The other two strategies not listed here are for temperate regions) Of those listed above, strategy #5 cannot be employed in wann humid climates because. the underground temperatures in these regions are above 78° F which is beyond comfort range (Labs, 1989:201). Silnilarly, the hedge and fence siting requirement by the city of Davis, California (#7) does not apply to warm-humid climates since this is a requirement in climates which also have a heating need. Hence the applicable cooling-need reduction strategies will be as follows:

Number

u.s. de~

County Port Arthur, .

2

Sacramento,

3

Dade County

4

Boulder, Cole

5

Douglas Cou

6

King County,

7

Davis, Califo

8

Davis, Califo

9

Davis, Califo

Source: Adapted from Erle

• Landscaping re

Reduction of Transpj The way urban activ tween them. The gn need for transportatio the energy spent on tJ as Correa says, "ease of clogging" (Correa,

At the same time, til{ other words, density. while height increase~

• Site & Building orientation for avoidance of sun

Indian Standards for 1 = 475 ft2 plot

• Site & Building orientation for encouraging air movement

5-story walk-up apart

• Shading device requirements for open spaces

20-story apartment bl'

Journal of Architectural and Planning Research 12: 1 (Spring, 1995) 61

TABLE 2. Some U.S. design guidelines for the reduction of energy needs for space-conditioning.

County

Description

Date of Enactment

Port Arthur, Texas

Sub-division regulation that requires passive solar orientation of sites to reduce solar ex posure of buildings and windows in summer (See Figure 1)

Sept. 1979

2

Sacramento, California

Street and lot orientation encouraging buildings to be oriented for passive heating and cooling. (Figure 2)

1977

3

Dade County, Florida

Site plan review criteria incorporating require ments for energy efficient orientation

1975

4

Boulder, Colorado

Incentives to encourage energy efficient site layout

Aug. 1977

Douglas County, Kansas

Permission to build "earth sheltered" buildings

Mar. 1979

Number

~.

U.s. were identified

5 r

Ie very fonn of the rd manner and there ann will help direct the need be, ensure , in California is an i region was found, of eleven examples reduction of space

6

King County, Washington Permission to develop "townhouse" type dwellings of high density

7

Davis, California

Flexible siting of hedges and fences so as not to 1979 interfere with heat collection

8

Davis, California

Permission to use shading devices even within open spaces

1979

9

Davis, California

50% landscaping requirement for parking lots

1979

Dec. 1979

Source: Adapted from Erley & Mossena, 1980, pp. 8-15.

• Landscaping requirements for heat-gain reduction.

Reduction of Transportation Energy Needs

enacted by regions)

1S

~

The way urban activities are organized, influences the way energy is spent in commuting be tween them. The greater the diversity of activities at a given place, lesser therefore will be the need for transportation. The solution lies in providing the right mix of activities that will reduce the energy spent on transportation. The goal is not to smooth traffic, rather to reduce them. FOf, as Correa says, "ease of transportation is not an end in itself. Journeys always multiply to a point of clogging (Correa, 1989:73). tt

imates because. the omfort range (Labs, tf Davis, California ;limates which also rill be as follows:

At the same time, the efficiency of urb3I1 activities depends on the number of people served. In other words, density. And density is not necessarily proportional to height. Correa shows that while height increases twenty fold, density increase is only four-fold (Correa, 1989:39). Indian Standards for ground floor housing = 475 ft2 plot

= 50 families per Acre

5-story walk-up apartment density = 100 families per Acre 20-story apartment block

= 200 families per Acre


N

Allowable

Range

Allowoble

range of Site oiler

I I

S

Optimum Orientation

FIGURE 1. Solar building orientation. Source: David & Mossena, 1980, pp. 8-9.

Several theoretical attempts at defining low-rise, high-density development were found (Correa, 1989; Soon, 1989; etc.). Most strategies related to residential or mixed use development. Correa drew from his experience in planning a new extension to Bombay, India (Correa, 1989). In this model, he proposed a housing density of 638 per Acre or 63 households/4300 ft2 or 7 households/690 ft2 . This model is single-storied development, but town-house development with greater densities is also possible (Lim, 1980). However, higher density dwellings are not always warranted. The use of alternative sources of energy sometimes makes higher densities unaccep table. For example, a density of 20 families/acre, is the upper limit, if bio-mass is to be used as a source of energy (Correa, 1989:106). Another strategy for dealing with density is to restrict plot sizes. In the Indian context, Correa (1989) suggested a medium size of 540-1080 ft2 in his new Bombay proposals and found that

FIGUR

acceptable for both tb urban design guideline those proposed by Cor

Journal of Architectural and Planning Research 12:1 (Spring~ 1995) 63

Building

Line

Li e of Or entation

N ----- .........

Rear Space

-------'------'---- Lin e

N Allowoble ronge of Site orientotion

IdeolOrientation

8-9.

vere found

(Corre~

~velopment.

ldia (Correa, 1989). holds/4300 ft2 or 7 e development with lings are not always r densities unaccep ss is to be used as a lian context, Correa

,sals and found that

FIGURE 2. Determining lot orientation. Source: Erley & Mossena, 1980, p. 10

acceptable for both the poor and the affluent sections of the society. Of the energy conscious urban design guidelines surveyed both in the U.S and the U.K., none came to as high densities as those proposed by Correa and others for third world cities.


..

=-~

--

~ TABLE 3. Some U.S, url

-~

Bus 'Route

Community Boulder, Colorado

MRT Inter-change

Windsor, Connecticut

Inter-change Davis, California Source: Erley & Massena,

In addition to the at needs, and transporu energy requirements the fonn of reducir Washington; and Da'

As traffic grows, a secondary bus route can be installed, opening up a whole new section of the hinterland.

Bus Route

MRT

Bus ROLJ'te

FIGURE 3. Mass transportation loops. Source: Corea, 1989, p. 70.

The most directly energy conscious approach encountered by the survey at the urban scale was Correa's proposal for New Bombay which had a system of mass transportation loops that permits smooth movement while preserving the self-contained nature of individual clusters (Figure 3). However, many authors, including Correa agree that the most energy-efficient mode of transpor tation is bicycle, closely followed by public transportation (Illich, 1974; Matthews, 1985; Owens, 1986, 1987; Correa, 1989; etc.). As such the most energy efficient urban transportation strategy will be the encouragement of the use of bicycle. The problem of riding bicycles in warm-humid cities is posed by the high air temperature coupled with high relative hUlnidity and traffic conges tion. To encourage use of bicycles, therefore, shaded pathways exclusively designated for bicycles can be provided. In addition to the overall strategies mentioned above, several neighborhood and intra-urban scale strategies were also encountered. These relate to one of the following: • Incentives for energy-efficient site development • Greater diversity • Multi-use land development.

Outstanding Issues If the design guidelil that buildings and n( site orientation than design choices. In the warm-humid i difficult to set desi~ topography that are , ing needs must be fll sena, 1980:30).

Landscaping regulati, concise table of infol qualities (area of sha( Similarly, guidelines simplify the process, shading at different 0 Conceding that these employ the principle~· study. CASE STUDY:

DEVELOPMENTF

Before the principles to the city of Colom


TABLE 3. Some U.S. urban guidelines for the reduction of transportation needs.

Community

Guideline

Date of Enactment

Boulder, Colorado

New development to be located near existing facilities

Aug. 1977

Windsor, Connecticut

Encourage conversion of one- or twofamily houses into multi-family buildings

1976

Davis, California

Encourage home occupations

April 1979

e Source: Erley & Mossena, 1980, pp. 8-20

In addition to the above-mentioned aspects of energy conservation (city form, density, cooling needs, and transportation needs) the APA study also found regulations that reduce the embodied energy requirements (i.e. energy spent in the construction of urban elements). These usually take the form of reducing street widths. Three examples (Windsor, Connecticut; King County, Waspington; and Davis, California) were reported by the above study. Route

Route

Outstanding Issues If the design guidelines are to be effective in tenus of reducing cooling needs, they must ensure that buildings and not just sites are oriented properly. At the urban scale, it is easier to control site orientation than building orientation without infringing too much upon individual designers' design choices. In the warm-humid zone, ventilation plays an important part in thermal comfort. However, it is difficult to set design guidelines for ventilation, as it depends on micro-climatic factors like topography that are very site specific. In order to be effective, regulations for reduction of cool ing needs must be flexible, like trade-offs between orientation, window size, etc. (Erley & Mos sena, 1980:30).

the urban scale was loops that pennits clusters (Figure 3). nt mode of transpor thews, 1985; Owens, ansportation strategy feles in warm-humid y and traffic conges lvel y designated for ~n

md intra-urban scale

Landscaping regulations need to be specific about types of trees, etc. It is necessary to develop a concise table of information specifying common warm-humid zone trees and their environmental qualities (area of shading, resistance to wind flow, etc). Similarly, guidelines related to shading need complex formulae for calculation. In order to simplify the process, it is necessary to develop shadow tables that specify the amount of required shading at different orientation for a given location. Conceding that these and other unanswered issues exist, it is still possible for us to attempt to employ the principles enumerated thus far to a warm, humid city which is the main focus of the study.

CASE STUDY: COLOMBO, SRI LANKA DEVELOPMENT PLAN

ANALYSIS OF THE COLOMBO

Before the principles and strategies for energy-conscious urban design guidelines can be applied to the city of Colombo, it is necessary to identify the problems with the existing development

Joumal of Architectural and Planning Research 12:1 (Spring, 1995)

model. Present developments in Colombo are governed by a legal document called City Of Colombo Development Plan, pub lished by the Urban Development Authority of Sri Lanka, empowered by an Act of Par

liament (Law No. 41 of 1978) to plan, regu

late, and implement development in urban areas of Sri Lanka. This publication out

lines the development regulations applicable

to the city of Colombo. The following

analysis is intended to highlight the

deficiencies in Colombo's city planning in terms of energy use. Textual references are to the above document.

66

TABLE 4. Specific cha

N

l' /

Planning Unit Fort Kochchikade Maradana Kollupitiya

"

\

\

Mattakuliya

I

I I

,

Kotahena

I

\

\

General Characteristics of the City

The physical structure of Colombo is similar to many of the colonial port cities. The fort was the focal point around which were established residential areas of white settlers and residences of local inhabitants some distance from it. In the course of time, the fort became the financial and government center and PettalI (an outlying area adjacent to the old Fort) a center for retail and wholesale trade serving the needs of a growing city and entire Sri Lanka. In dustries were established close to this area where the railway was also located. New developments were guided by the com munication routes and the terrain (Vol 1:8).

-, ,-,\,

M",i"

,

..

- - I(",,{fie.

, ,

, I

' '

/

/

A'+c.,..i~?

~ -r,.."".({ic. f.-Jodes

----J~b-d;v';sio"s

Grandpass Dematagoda Borella Cinnamon Gardens

/ ~

I

Bambalapitiya

:

A

\_/,,./

Wellawatte

Narahenpita Kirillapone Total Area FIGURE 4. City of Colombo, traffic arteries, natural features, etc.

Colombo is hemmed by marshes on the east, Kelani Ganga, the most voluminous river in Sri Lanka on the Northeast, and the Indian Ocean on the West. The development pattern has been an elongated north-south linear model along the major highway to southern Sri Lanka (Figure 4). While the central part of the city houses parks and spacious bungalows, the edges, particularly eastern and south-eastern parts, are dominated by shanties and slums. Specific Characteristics of the City Subdivisions

The city of Colombo is divided into fourteen planning units, covering a total extent of 9224 acres (14.4 sq. miles). The specific characteristics of each subdivisions are as follows.

Source: Adapted from C(

Land Use Pattern

Colombo is predon

Surprisingly, the sec

The CBD, comprise

daytime population

(in 1981) was 585,~

eastern fringe. Ho\\

state agencies are cu

Energy-Consuming

Population and Residential Density

• Colombo is a The city of Colombo had an overall population of 585,776 in 1981 (last year of official census). This worked out to a gross density of 157 persons/Ha (64 persons per acre). However, a much higher residential density prevails in all the planning divisions.

Journal of Architectural and Planning Research 12:1 (Spring~ 1995) 67

TABLE 4. Specific characteristics of Colombo~s sub-divisions.

N

l'

,

--

M~it'\

T"Affi~

Arfe..rif!.$

~ ~ -r..~tric.. t-.lodes /

----J