The Use of Passive Cooling Strategies in Dubai, Moving Towards Sustainability

8/14/2019 The Use of Passive Cooling Strategies in Dubai, Moving Towards Sustainability

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Ecocity World Summit 2008 Proceedings

THE USE OF PASSIVE COOLING STRATEGIES IN DUBAI

MOVING TOWARDS SUSTAINABILITY

MAHMOUD A. HAGGAG, UAE UNIVERSITY

[email protected]

ABSTRACT

Hot and humid climates, such as those in Dubai, generate unique challenges to architects and engineers,

seeking for passive cooling approaches to reduce energy consumption in buildings. They are collaborating

to design new buildings that are energy efficient, environmentally friendly, and architecturally glossy.

Passive cooling techniques are highly energy efficient and can be considered as a good alternative to

mechanical cooling systems. The cost and energy effectiveness of these techniques are worth considering

not only by builders but also by buildings' occupants. Sustainable buildings that are passively designed

take advantage of natural energy flows to maintain thermal comfort, reduce cooling costs, and reduce

greenhouse gases that contribute to global warming.

Despite the fact that Dubai is one of the hottest cities in the Gulf region, the use of glazed facades in

modern buildings has gained increasing popularity throughout the city. Builders, owners, and occupantslike the idea of good views, a pleasant indoor environment, and building's prestige. These strategies

usually come with an increased operational cost due to the higher solar gain which increases the air-

conditioning cost. In many parts of the world, the design of passive cooling systems has been used to

overcome this major disadvantage of using glazed facades. Passive cooling design is already recognized

in the traditional architectural fabric of old Dubai (Bastikia and Shindagha districts). It is also applied to a

few modern buildings within the new urban development such as Madinat Jumeirah.

This paper attempts to reduce energy consumptions in buildings by adopting passive cooling strategies in

the modern building process in Dubai. Based on the lessons of experiences which can be learned from the

traditional architectural ideologies, three passive cooling strategies are investigated in the study: natural

ventilation, thermal mass and shading strategies.

Keywords: sustainable development; passive cooling; energy efficient; Dubai.

INTRODUCTION

Dubai has undergone a reorientation from federal city to international node in the global network. The

architectural ideologies of Dubai have moved from a traditional pattern to modern development. The

traditional fabric reflects architectural and planning ideologies of the pre-modern era. This pattern,

responding to the hot climate, was characterized by high-density buildings, narrow shaded alleys,

courtyards, small windows, and wind-towers. The alleys tended to run from north to south and ended at

the creek, permitting the prevailing winds to pass through. Modern architectural ideologies have been

recognized during the second half the 19th century with fast urban development. The character oftraditional buildings has been changed completely. Dubai became one of the most modern and global

cities, boasting the highest glass tower in the world (Burj Dubai). The city is currently constructing

superlative mega-projects including the man-made residential islands (the Palms), the world project (300

artificial islands), the man-made Arabian Canal (new communities), Dubai Land (an entertainment, retail,

and sports project), Falcon City of wonders (a commercial, residential, educational, and entertainment

project), and Dubai Metro project [1]. The trend for such urban development has a major consequence on

levels of energy consumption and its impact on the urban environment. Minimizing the impact of urban

development on the natural environment and the use of passive solar strategies are the main concern of

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the study.

Focusing on the climatic conditions of Dubai, the paper attempts to reduce energy consumption and

increase occupants' comfort by adopting passive techniques. Attention is given to the principles of green

architecture, sustainable energy, and passive cooling strategies. The study findings show that sustainable

building practices in terms of cooling load reductions have been acknowledged not only in the traditional

buildings of old Dubai, but also in some recent projects such as Madinat Jumeirah, the case study of this paper, which was designed and built in an ecological and resource-efficient manner.

HISTORICAL PERSPECTIVE

Dubai, the second largest of the seven emirates of the United Arab Emirates (UAE) after Abu Dhabi, has

become one of the most modern cities in the world; boasting the highest skyline in the Middle East with

12 buildings over 305 metres [2]. The city started its urbanization process in the late 18th century with a

small fishing and trading village in the Arabian Gulf. It is divided into two parts: old Dubai, with its

traditional ideologies, and new Dubai, with its modern architecture.

Dubai has the largest population in the UAE with about 1.5 million people, expected to reach 3 million in

2020 [3]. The demography of the city comprises a varied mix of nationalities and cultures. The strength ofthe Dubai economy is boosted mainly by the ports and national resources such as petroleum and natural

gas. In 1972, an enormous project, "Rashed Port", was constructed. A few years later, "Jabal Ali", the

industrial centre, was built and become the biggest man-made harbor in the world and a chief tourist

destination and port in Dubai.

Dubai, with its hot climate, is situated 25 degrees north and 55 degrees east, within a sub-region of the

northern desert belt. It is characterized by scarce rainfall and high levels for temperature, humidity and

sunshine. In summer time, the weather is very hot and humid with daytime temperatures ranging from

35◦C to 49◦C. In winter, the daytime temperatures range from 25◦C to 35◦C, and sometimes falling to aslow as 9◦C at night [4].

Dubai and its Urban Development

Dubai has been significantly shaped by various imported ideologies: Arab, Persian and British. The fast

urban development that followed the 1971 UAE federation and the discovery of oil completely changed

the character of the city from traditional architectural fabric to modern style. The rapid transformation of

Dubai and its wider urban region during the last few decades demands greater critical analysis. Three

issues motivate this transformation. The first and most important theme is the Emirate of Dubai as an

international trading center "global city". The second motivation concerns the dramatic nature of the city

development; including population increase, and spatial expansion and economic growth. The third theme

is the emerging status of the city as an urban region. Much urban development, including Rashid Port,

Jabal Ali Industrial Center, the Free Zone, Metro Dubai and other projects have increased trade activities

and accelerated open-door policies of urbanization.

The architectural ideologies in Dubai have been moved from a traditional vernacular style to a modernapproach. The traditional fabric reflects three dominant factors: the climatic condition, the cultures and

customs of the residents, and the locally available building materials. This pattern is characterized byhigh-density buildings, narrow shaded alleys, courtyard houses and wind-towers. The modern approach,

which was established during the second half of the 20th century, was concerned with highly specialized

building techniques. Building industry and urban fabric had been strongly affected by two factors. First:

the importing of building materials and the establishment of foreign factories in the city. Second: planning

organization was based mainly on occidental codes and dominated by foreign professionals [5]. This

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modern style is highly recognized within the new central area of Dubai. A number of enormous mega-

projects have been constructed, including Dubai Marina (a master planned community for 40,000 people

located in the centre of Jumeirah); Emirates Mall (one of the largest shopping malls in the world), and

Madinat Jumeirah (the largest modern resort in Dubai).

Old Dubai lies on the trip of a small line of salty water extending inland from the Creek, which divides

Dubai historical area into west side "Bur Dubai" and east side "Deira". Bur Dubai contains the oldesttraditional districts like Bastikia (1910), and Shindagha (1896). Deira contains the Great Souk (1920), Al-

Ras residential areas, and the Gold Market. This fabric is characterized by narrow shaded alleys, tall

wind-towers (Barajils), and courtyards, which provide natural cooling system to maintain a comfortable

indoor temperature (see figure 1). Another characteristic of the traditional townscape was that the

buildings tended to be very closely clustered together separated by narrow lanes running from north to

south to permit the prevailing winds to pass through.

a) Shindagha District, old Dubai b) Bastikia District, Old Dubai

Figure 1: Traditional urban fabric of old Dubai [6]

New Dubai, with its modern architectural style lies mainly on Sheikh Zayed Road, the new centre of

Dubai (see figure 2).

Figure 2: Urban development of Sheikh Zayed Road (December 2007)

Sheik Saeed Al-Maktoum House, built in 1896, is a typical example of the traditional architecture in

Dubai (see figure 3). It was the former ruler’s residence (1912–1958). In 1986, it was converted into aMuseum of Historical Photography and Documents of Dubai. The living quarters of the house open on to

the main courtyard to generate wind circulation around the rooms. Most of the rooms are provided with ashaded verandah overlooking the courtyard. Windows are mostly on the inside looking in towards the

courtyard. Windows on the exterior walls are limited to narrow slits and semi-decorative openings which

admit light and accelerate natural ventilation for the house. The wooden ventilating screens (Mashrabbia)

were also used to keep out the sun, allow the passage of cool breezes, and provide privacy. The wind-

towers were the most distinctive architectural elements of the house. They have four open sides. Theywere designed to trap the wind from any direction then direct it through a hollow shaft to the indoor space

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below. Wind-towers take advantage of natural ventilation to bring fresh cooling air through the house

without mechanical systems. Such systems incorporate operable windows to increase the airflow inside

the house. The house was built from local high mass materials including coral stone, lime, plaster, and

palm fronds. Such materials have adequate thermal storage which responds to the needs of the climate.

Figure 3: Sheik Saeed Al-Maktoum House, Shindagha, Dubai

The trend of urban development, which is rapidly experienced in Dubai, has negative impacts on theenvironmental aspects including environmental deterioration, high consumption level of non-renewable

recourses, and high level of air pollution. Minimizing this impact on the natural environment and the

efforts to improve the ecological performance of any project are the main concerns of sustainable building

development during and after construction period [8]. Thus, energy efficiency, healthy environment, and

the protection of biodiversity are the key issues. In the developed countries, buildings consume about45% of total energy use; 25% of total water consumption; 70% of total electricity consumption, and about

40% of total carbon dioxide emissions [9]. These figures are even higher in Dubai [10]. Dubai has been

listed as one of the highest per capita fossil fuel consumption and carbon dioxide generation. Meanwhile,

it has been listed on the top in consuming energy per capita [9]. Despite that fact, the environmental

impact of buildings is often underestimated, while the costs of building green are overestimated.

Therefore sustainable building practices, in term of energy consumption, are essential in cities like Dubai

in order to adapt environmentally friendly conditions. The main question could be asked is: "how could

cities with rapid urban development, like Dubai, sustain their building practices in term of energy

consumption?"

TOWARDS SUSTAINABILITY

The concept of sustainability states that there is a need to improve the living conditions of the present

generations without compromising the ability of future generations to meet their needs. Sustainable

development refers to a socio-ecological process characterized by the fulfillment of human needs while

maintaining the quality of the natural environment. Achieving sustainable development means:

developing new forms of multilateral cooperation; extension and sharing of new technologies; increasing

international development; removal of artificial barriers to commerce; and expanding global trade [11].

Sustainable development could be achieved by architects, engineers, designers, town planners, and

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manufacturers of building products working cooperatively to produce green buildings that are designed,

built, renovated, operated, or reused in an ecological and resource efficient manner. Green Building or

Green Architecture is an approach to architectural design that emphasizes the place of buildings within

both local ecosystems and the global environment. Green building is the practice of increasing energy

efficiency, while reducing building impact on human health and the environment through better siting,

design, construction, operation and maintenance. A similar concept is natural building which tends to

focus on the use of natural materials, renewable recourses, and passive solar techniques [12].

Effective green buildings require careful attention to the full life cycle impact of resources. Building

materials, one of the key issues of sustainable architecture, should be "green" and obtained from local

sources including rapidly renewable plant materials like palm fronds and bamboo, coral stone, recycled

material, and other products that are reusable and renewable. Low impact building materials should be

used wherever feasible, for instance, insulation may be made from low volatile organic compounds rather

than building insulation materials that may contain toxic materials [12]. Reducing energy loads is another

issue for green architecture. It is important to orient the building to take advantage of cooling breezes in a

hot climate, and sunlight in a cold climate. To minimize the energy loads, passive solar design can be

effective. Masonry building materials with high thermal mass are efficient for retaining the cool

temperatures of night throughout the day. Moreover, buildings are often designed to capture cool winds.

Many of these valuable strategies are employed in the traditional architecture of old Dubai.

The most important characteristic of passive solar design is that it relies on the integration of a building's

architecture, materials selection and mechanical systems to reduce heating and cooling loads. It takes into

consideration local climate conditions, such as temperature, solar radiation and wind; to create climate-

responsive, energy conserving structures that can be powered with renewable energy resources [13].

Passive solar design also helps conserve valuable fossil fuel resources and reduces greenhouse gases that

contribute to global warming. The most important step in the passive cooling process is to develop an

energy efficient building envelope to minimize heat gains and to catch cooling breezes. Depending on the

climatic condition, passive solar design of the building envelope might comprise the following concerns:

orienting more windows to the north; incorporating adequate shading devices that prevent solar radiation;

incorporating thermally massive building materials; providing suitable insulation; using high performance

glazing that reduce heat gain and admit natural light. Landscape and outdoor spaces also play an

important role in passive cooling strategies. Vegetation, water ponds and fountains are efficient elementsin the cooling techniques.

In Dubai's hot climate, where cooling is a primary concern, much can be done to capture natural breezes

to keep buildings cool and comfortable. Combining proper ventilation, courtyards, wind-towers, shading

devices, thermal mass, and insulations can reduce energy loads for cooling.

PASSIVE COOLING STRATEGIES

A natural passive cooling system is an option to sustain a cool building and reduce air conditioning costs.

It uses non-mechanical techniques to maintain a comfortable indoor temperature. The most effective

method to cool the building is to keep the heat from building up in the first place. The primary source is

sunlight absorbed through the roof, walls, and windows (heat gain). To prevent it, specific strategiesshould be applied; including reflecting heat, blocking the heat, and removing built-up heat [14].

About 30% of the unwanted heat comes in through the building roof, and more than 40% comes in

through windows [14]. To minimize the effect of radiant energy, a reflective waterproof coating is

essential. Another way to reflect heat is to install a radiant barrier on the underside of the roof. This can

reduce heat gains by about 25% [14]. Light-colored surfaces effectively reflect most of the heat. The use

of reflective window coatings can also reduce the heat gain by about 35% [15]. The use of sun-coating

films is one solution for hot climates since they can reflect as much as 80% of the incoming sunlight [14].

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Shading, insulation, and landscaping are good strategies to block the heat and keep the indoor temperature

cooler. Shading is a key issue in any passive cooling strategy. In most cases, shading can reduce indoor

temperatures by 10◦C [14]. Effective shading can be provided by trees and shading devices. As part of the

landscape design, well-placed trees can provide effective shade. The shape, height, growth rate, and

branch spread are factors to consider in choosing the right type of tree.

Shading devices, both exterior and interior devices, control heat gain. Exterior shading devices are moreeffective since they block sunlight before it enters windows. They include awnings devices, louver

devices, shutters, and solar screens. Awning devices, which are usually attached above the windows and

extend down and out, can reduce heat gain by up to 65% on southern windows and 77% on eastern

windows [14]. Louver devices can be adjusted to control the level of the sunlight entering the windows.

The slats can be vertical (on the eastern and western windows) or horizontal (on the southern windows).

Shutters, when closed, keep sunlight out, but they block the light. Solar screens keep direct sunlight from

entering the windows, reduce glare, and block light without blocking the view or eliminating the air-flow.

Insulation helps seal and protects buildings against the heat. The upper roof, which is the major source of

heat gain, is the most important place to start insulating. Wall insulation is not so important as roof

insulation because of differences in outdoor temperature between roof and wall. Floor insulation has little

and sometimes no effect on cooling. Stopping air penetration around poorly sealed doors, windows, and

exterior walls air is important issue to keep the indoor space cool. Most of these air leaks can be achievedthrough weather-stripping and caulking.

Natural ventilation helps remove heat and maintains indoor temperatures close to outdoor temperature.

This strategy only works when the inside temperature is higher than outside temperature. In hot-humid

climates, a building designed for passive cooling would be as open as possible to ensure the maximum

possible cross ventilation [16]. East and west walls should have a minimum of windows or none at all in

order to exclude the low angle sun-rays. However, north and south walls should have enough windows to

allow cross ventilation. The spacing of buildings should be carefully considered to avoid obstruction ofthe wind. Using wing-walls, vertical overhang panels placed alongside windows can accelerate the natural

air flow due to pressure differences. Cross ventilation can also be enhanced by irregular-shaped, spread-

out buildings. A thermal chimney can also be used to ensure ventilation by creating a warm zone with an

exterior outlet. The wind-tower is another dramatic device for using the cooling potential of the available

breezes. Wind-tower, which is the key element in the traditional architecture of Dubai, is a vertical shaft

with vents on top to lead the desired wind to the indoor spaces (see figure 4).

Figure 4: The role of courtyards and wind-towers in the cooling passive strategies

The courtyard is a common architectural feature and is considered as a microclimate modifier, which may

improve thermal comfort conditions in the enclosed as well as the attached built volume. The courtyard

provides thermal environmental conditions through its design concept, forms and heights. During the day,

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the shading arcades, trees, and vegetation protect the building from direct solar gain, and the cool mass in

the courtyard floor absorbs a significant amount of solar radiation (see figure 4). A massive courtyard

floor surrounded by a building provides cooling, primarily by radiation to the cool, clear night sky. The

night time radiation cools the mass and the air trapped in the courtyard.

MADINAT JUMEIRAH

Madinat Jumeirah (City of Jumeirah), the largest resort in Dubai, was constructed in 2004 and situated in

the heart of new Dubai; adjacent to Burj Al-Arab Hotel, Wild Water Park, and Jumeirah Beach Hotel. Itreflects the rich cultural heritage of Dubai and resembles an ancient Arabian architectural style. Madinat

Jumeirah comprises two 300 room hotels (Al-Qasr and Mina Al-Salam), courtyard summer houses (Dar

Al-Masyaf), a traditional souk and cultural village, a Conference and Banqueting Centre, and recreational

and health facilities (see figures 5-a, 5-b, 5-c and 5-d). It has a series of canals and lakes flowing between

the buildings. Nearly 4km of waterway runs through the entire complex. Madinat Jumeirah forms avirtual island looking down upon wind-towers, courtyard houses, pools, meandering waterways with

traditional water taxis (abbras), and a private beach.

The outstanding architectural concept of Madinat Jumeirah was based on a theme of old Dubai in a

luxurious context. Madinat Jumeirah has been designed by an international multidisciplinary design firm(Creative Kingdom) and developed by Mirage Mille. The project was designed and built in an ecological

and resource-efficient manner. The combination of green design techniques used in the project will not

only reduce energy consumption and environmental impact, but also reduce running cost, create more

pleasant indoor spaces, improve occupants' health, and reduce pollution and legal liability.

5-a) Al-Qasr Hotel 5-b) Mina Al-Salam Hotel

5-c) Dar Al-Masyaf (courtyard summer houses)

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5-d) The Souk (market)

Figure 5: the use of passive cooling strategies in Madinat Jumeirah (shading devises, natural ventilation,

courtyards, wind-towers, thermal mass, and landscaping)

Various concepts and techniques were used to design and develop energy-efficient buildings and cooling

load avoidance in Madinat Jumeirah. Design strategies that minimize the need for mechanical coolingsystems were adapted. These strategies include proper shading, natural ventilation, thermal mass, careful

siting and orientation decisions, and good landscaping. Some of these strategies are described below:

- Fixed shading devices are installed mainly on the south-facing windows. They are carefully designed

to allow the sun to penetrate only during determined times of the year. In the summer, the overhangs

block the high sun; however they allow the low winter sun to enter the windows.

- Trees and vegetation are properly located and used for shading. Vegetation, pools and canals around

buildings contribute to an evaporative cooling strategy.

- East and west windows are limited and the majority of them are north-facing windows to reduce

direct solar gain.

- Buildings were designed to take advantage of natural ventilation which uses the passive stack effect

and pressure differential to bring fresh cooling air through buildings with limited or no mechanical

systems. This strategy has been adapted by incorporating different means of outdoor air intake,

including operable windows.

- The wind-tower, an effective device for natural ventilation, has been used to increase the air flow in

buildings. Other features include fresh air inlets located near floor level, use of atriums, and

courtyards that have been adapted to enhance the stack effect and to speed the indoor air flow.

Courtyards have been used not only to improve indoor comfort but also to provide a pleasant outdoor

environment. They help achieve desirable thermal environmental conditions not by mechanical

devices but by architectural design (form, materials, floor covers and landscaping).

- External insulated, dense materials like concrete, bricks, and other masonry covered with plaster have

been used in passive design to absorb, store, and re-release thermal energy. This strategy increases

comfort and reduces energy consumption by moderating internal temperatures by average day/night

extremes.

CONCLUSION

Recent ongoing developments in Dubai have consequences on the urban environment. Minimizing the

impact of urban development on the natural environment and the trend to improve the ecological performance of buildings are the main concerns of the sustainable building practices in the city. These

ideologies have been acknowledged by international architectural firms to design and construct new

projects that are energy efficient, environmental friendly, and architecturally remarkable. Many architects

and developers, like ”Creative Kingdom" and "Mirage Mille" have already incorporated ecological and

sustainable approaches in their designs. Madinat Jumeirah, which is considered among the unique projects to maintain the new vision of Dubai, is a significant development regarding sustainable practices

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that aim to reduce cooling loads and increase occupants' comfort. Various concepts and techniques have

been used to develop energy-efficient buildings and cooling load avoidance. The use of natural

ventilation, thermal mass, proper shading, careful siting and landscaping have been adopted in the project

as passive cooling strategies. In addition to these strategies, other cooling techniques have been used in

Madinat Jumeirah such as wind-towers and courtyards. The combination of the passive techniques used in

the project will not only reduce energy consumption and environmental impact, but also create more

pleasant indoor spaces.

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