Sustainable design for tall buildings in urban areas

The importance of Sustainable design for tall buildings in urban areas of the developed world

Introduction

During the 1950's it was recorded that 30% of people lived in urban areas throughout the world. In the year 2000 this figure climbed to 47%. The United Nations has recently projected that by the year 2030, this figure will rise to 60% of the world's population living in urban areas. This translates as 5 billion people. (United Nations, 2001)

Soaring land prices in these urban areas, and the decline of large areas of space on which to build has resulted in ever increasing demand for affordable residential and commercial properties over a minimal land area. A common solution for this problem is evident the world over; the construction of high-rise buildings otherwise known as skyscrapers. Examples of this can be clearly noted throughout the world's largest cities where the demand for these types of building is ever greater.

For more than a century, architects and civil engineers have applied practical and theoretical knowledge about vertical construction techniques to transform the look of cities. Despite this it has become apparent that the built environment is the greatest single indirect source of carbon emissions in the developed world, making them a major contributor to global warming.

Global warming, energy and water shortage, urban sprawl, air pollution, overflowing landfills, disease, and global conflict will be the legacy of the twenty-first century unless we move quickly towards the notion and implementation of sustainability.

Survival of the human race depends upon the survival of the cities--their built environment and the urban infrastructure. This will warrant vision, commitment, and action through partnership and commitment of governments, policy makers, experts, and the involvement of citizens. It will require collaboration of urban planners, architects, engineers, politicians, academics, and community groups.

Sustainable Architecture

The World Commision on Environment and Development (WCED) was established by the United Nations in 1983. It served to resolve the conflicts arising out of the aspirations of the developed and developing worlds. In 1989 the Brundtland Report was published which addressed the concept of “sustainable development”. As part of the UN's WCED, it called for “Sustainable development; which meets the needs of the present generation without compromising the ability of future generations to meet their own needs.”

This called for the challenge of architects and civil engineers to create sustainable architecture, defined as environmentally conscious and energy-saving, whilst being able to utilize responsive and renewable materials and systems (Newman, 2001). Ecological and environmental concerns have expanded beyond the issue of the consumption of non-renewable energy sources. Sustainability essentially aims for ecological balance.

The High Performance Tall Building:

The area in which a tall building is placed is of vital importance to the urban environment. Due to the size and nature of a tall building, the effect on the surroundings can be enormous; this includes the contribution to the urban heat island effect, overshadowing, large scale waste production and the effect on local services.

The internal environment of the building also needs careful consideration. Inner cities are renowned for their own microclimate, often comprising of heavily polluted external air conditions, for this reason the internal air quality of a tall building needs to be maintained at a high standard. During the construction phase there is potential of the use of toxic materials and chemicals used in building components, systems and furnishings, all of which are of great concern to building users, and other users of surrounding buildings.

For these reasons, sustainable design of a tall building is a term which applies to the careful consideration of design, construction and maintenance of the building including its performance in its working life. This means that we have the ability to minimize or ideally eliminate the negative impact on the local and global environment including its users.

High rise buildings consume vast amounts of energy both in the construction and working life phase. Even though they are the central elements of urban architecture due to the scale and purpose of their construction, they should have a focus on sustainable development. A high rise building that meets the requirements of sustainable design is one that has optimum efficiency of function and performance via the use of sustainable technology providing reduced energy consumption and the reduction of negative environmental impacts.

Therefore a high rise building requires an incredibly in-depth understanding of the local and global environment and its resultant impact on the local environment specifically. Construction and community elements of the project must combine through expert advice and assessment from field experts. This includes architects, civil engineers and city planning agencies in regards to design and construction and the input of community groups, physiologists, and social experts with regards to the impact on the community. Both groups need to combine in harmony to produce a sustainable design which will benefit from high building performance, optimum energy efficiency, and limited negative local environmental impact, non-renewable material conservation, and limited pollution during construction and active life, provide a high standard internal environment and create a structure that aesthetically harmonises with existing surrounding buildings.

The Design Factors

Due to the size of the task of building tall structures, there a several factors to take into account when designing sustainable tall buildings:

- Site context

The assessment of all physical aspects attached to and surrounding the site including the specific location of the site. This includes site access for construction and access for its users after completion.

- Environment

The economical, social and physical environment will be affected locally and possibly globally by a tall buildings construction, especially if building super-tall structures. All aspects of which must be taken into account through careful planning and design from industry professionals.

- Structural form

The form of the proposed tall building is important in the design phase as this means dealing with the analysis and design of structures that support or resist loads that will be relevant to the local climate i.e. Wind loading will be greater in specific geological areas.

- Materials

The use of renewable or non-renewable materials is perhaps one of the most important factors of the design and construction. This has an immediate effect on the sustainability of the tall build project. Where these materials are sourced is also important, a local source is optimum.

- Energy use

A design target set to offer optimum energy performance of a building resulting in reduced life time energy costs through implementation of energy efficient technologies including intelligent heating and ventilation systems and solar design.

- Water utilization

- Ecological impact

- Community impact

- Local architectural style

Due to the extent of construction and the relatively confined inner city space in which to build, these factors are magnified due to their impact on the immediate local environment. All parties involved in the design and construction process, need to be aware of the goal of optimum sustainability to enable the team to achieve all the sustainability goals set. These goals must be clear and achievable.

Building Integration Systems (BIS)

High rise buildings in confined inner city areas require optimum performance if they are to meet the high standards of sustainable development. This requires the integration of architectural design and civil/structural engineering. This integration is a key factor in the success of a high rise “green” building. The term “green” often refers to the carbon output of a building and can apply to the variety of sustainable features a building has, and resultantly how sustainable the development is.

This integration of architectural and engineering professionals will consider every aspect of the design in order to produce a suitable building integration system. The factors taken into account are:

- Daylighting design

- Building orientation

- Building height (and number of floors)

- Exterior/Interior finishes

- Provision of services

- Lighting systems

- Ventilation systems

- Heating systems

- Air conditioning systems

- Acoustic design

- Vibration

- Computer applications (building control)

- Roof design (the use of water harvesting systems, green roof etc.)

- Drainage systems

- Aerodynamics

- Wind/structural loading

- Foundation system

- Insulation

- Plant location

- Building Form

Integration of hardware components of the building system provides the building with a range of technology based solutions and services that will increase efficiency and productivity. Importantly, these must share space with each other in the building, not compromise the aesthetic appeal of the building and work in harmony with each other.

Integration of tall building systems with special emphasis on sustainable design warrants a multidisciplinary approach and requires the integration of architectural components, structure, vertical transportation, fire safety, energy conservation, and communication systems. (ali & Armstrong!!!!!!!!!!!!!!***)

Types of integration

Bachman lists three types of integration: physical integration, visual integration, and performance integration.

Physical integration is about how components and systems share space and how they fit together. The floor-ceiling section of many buildings, for example, is subdivided into separate zones for lighting, ducts, and structure to support the floor above. These segregated volumes prevent “interference” between systems by providing adequate space for each system. Sometimes these systems are meshed together or unified, which requires careful physical integration.

Visual integration involves development of visual harmony among the many parts of a building and their agreement with the intended visual effects of design.

Performance integration has to do with “shared functions” in which a load-bearing wall, for instance, is both envelope and structure, so it unifies two functions into one element. It also involves “shared mandates” - meshing or overlapping functions of two components without actually combining the pieces. In a direct-gain passive solar heating system, for example, the floor of the sunlit space can share the thermal work of the envelope and the mechanical heating systems by providing thermal mass and storage. (ali & Armstrong !!!!!!!!!!!!!!!**************************) LIST ALL OF THE ABOVE AS REFERENCED)

Combining these types of integration can be a difficult task for engineers and architects. Therefore a common tool used for the integrated design of tall buildings is the “integration web”. It acts as a simplified plan of how building components interact with each other providing the design team a basis for which to begin designing the building integration system.

The Integration Web

The “integration web” for the design of a sustainable tall building. This is a vital tool in the process for sustainable and intelligent building design. All buildings require some form of integration of building components. Tall buildings however require a rather more in depth level of integration due to the complexity and scale of the building.

The Tall Building System Integration Web will facilitate the decision-making process at critical stages by clearly defining the relationships of each major physical system and subsystem of a tall building. It can also lead to the development of a methodology for performance evaluation of an integrated sustainable building in comparison to a conventional building designed without a focus on sustainability. (ali & armstong !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!)*****************

The cost of integration

It is important to remember that although fully integrated high rise, high performance buildings may cost more to build than a regular building, this is accounted for by a lower operational cost in the buildings lifetime, demonstrated by figure 1.

The break-even point of intersection in Figure 2 between the two curves depends upon the size and complexity of the building. Integrated innovative design does not necessarily represent high additional costs, although as shown in Fig. 1 the initial costs may be higher than that of conventional design with incomplete integration. However, its benefits are immense in that operating costs are lower and energy costs could be substantially lower compared with conventional solutions.

With continued implementation of integration techniques even the initial cost will eventually level off. (ali & Armstrong !!!!!!!!!!!!!!!!!!!!!!!!!!!!)

Building Case Study of Fully Integrated Design

Strategies for Achieving Sustainability

Architects and engineers have different views on the concept of sustainability. Architects assess the way a building is orientated in relation to the sun, a way the building is laid out, how the building interacts with the surrounding environment and how sustainable features can be applied to the fabric and finishes of a building. Engineers are concerned with the structural system and how this can aid energy conservation through intelligent design.

Combining the Architects and Engineers with the aid energy experts and field professionals, tall buildings in urban areas can be intelligently designed to respond to the local climate automatically. Some examples of which will be discussed later.

There are many options for the design team to take into account when undertaking a high rise sustainable project. Some of which are discussed below:

Passive Solar Gain:

Passive solar design in high rise structures varies considerably due to the location and climate of the project. The fundamental aim is to maximise sunlight entry to a building in the winter months and minimise excess sunlight in the summer months. This can be subject to alteration in extreme climate such as Dubai, where the Middle Eastern climate delivers intense sunlight almost constantly throughout the year.

Therefore passive solar design requires an understanding of the local seasonal solar geometry, new window and facade technology, and local seasonal climate. An in depth understanding of these factors can considerably increase thermal performance.

Good passive solar design can also reduce energy consumption through use of atriums allowing natural sunlight to fill a reception or entrance area to a high rise building, and use solar enrgy for direct or indirect heating of an internal space.

Active solar energy

Active solar utilizes the suns energy via collecting it using photovoltaic panels or solar panels. This harnesses the suns energy to create energy for a sustainable tall building. Photovoltaic's can produce integration of building hardware by incorporating an aesthetically pleasing facade with photovoltaic panels.

The major advantage of photovoltaics employed in a tall building is their ability to collect a direct stream of sunlight as they tower over surrounding buildings.

Structure and Material Preferences:

Construction uses over 420million tonnes of materials per year, produces 92m tonnes of construction and demolition waste per year (around 50% of which is recycled).

The impacts of this activity arise in many ways from initial extraction of raw material, the processing and manufacture of material, assembly and transportation of products, characteristics of the product in use, longevity, maintenance requirements, disposal issues etc.

Several factors need to be taken into account when selecting materials for a tall build project. These include the embodied energy of the selected materials, the cost of the materials, the source of the materials (possibility of recycled material), the maintenance costs and the possible disposal of the building at the end of its active lifetime.

Steel and reinforced concrete are the most popular choice to build with, but decisions can be made on the combination of materials to use in relation to the local climate, resultantly this can make huge impacts on the sustainability of the project. For instance, large concrete structures can be used in a desert-like climate to capture the cold night air and harvest it as cooling energy during the operational hours of the building. Furthermore, recycled steel can be used in the structural framework to add to the goal of achieving a sustainable development.

Furthermore, since the terrorist attacks on the World Trade Centre in New York City in 2001, the core structure and stability of tall buildings has never been more important. This relates directly to the materials chosen to provide a structural framework for the high rise building. The use of a concrete core can serve as protection from missile, bomb and aircraft impacts.

Façade Technology:

Since daylighting design has a large impact on the sustainability of the design, the facade may be one of the most important factors in controlling the daylight and shadow that enters a high rise structure.

The facade usually covers 95% of the external building surface. The facade has a fundamental impact on total energy consumption as a result of heat loss and gain. The control of heat loss and gain is the responsibility of the material and technology employed in the facade treatment. An intelligently designed facade can be used to control internal conditions of the building.

The latest trend is the use of double skin, and occasionally triple skin, façade with ventilation system (Behr, 2001). Double glazing with argon-filled cavities, triple-glazing and glass coatings can increase U-values (Pank et al., 2002).

Daylight has also been proven to have a large impact on the mental attitudes of the users of the building whether it is a commercial or residential building. The importance of the facade to control daylight entry should not be underestimated as its affect on the internal environment and the resultant effect on the user can be detrimental in the success or failure of the high rise building.

Harvesting Wind Energy:

Like solar energy, wind energy is a renewable resource that can provide unlimited supplies of energy for a sustainable tall building. The benefit of tall buildings is the fact that they are exposed to high altitudes where wind speeds are considerably greater than at ground level.

With careful design high rise structures can be aerodynamically designed to resist high wind speeds and simultaneously utilize them, via strategically placed wind turbines in areas where the structures profile is designed to amplify wind speed thus producing more energy with no risk to the safety of the buildings users.

Combined Heat and Power:

Combined Heat and Power (CHP) is the simultaneous generation of usable heat and power (usually electricity) in a single process. Through the use of an absorption cooling cycle, trigeneration or Combined Cooling Heat and Power (CCHP) schemes can also be developed. CHP is a highly efficient way to use both fossil and renewable fuels and can therefore make a significant contribution to the a tall buildings sustainable energy goals, bringing environmental, economic, social and energy security benefits.

The result is a cost saving and reduction of CO2 emissions of over 30 percent with respect to generation from coal-fired power stations and over 10 percent with respect to gas fired combined cycle gas turbines. CHP offers a flexible approach to low or zero carbon output tall buildings.

Fuel Cells:

Fuel cells are devices that convert the energy of a chemical reaction, typically between hydrogen and oxygen, directly into low-voltage DC electricity and into heat.

Although most fuel cells are still under development, they seem certain to play a large part in providing CHP in the hydrogen economy. For building applications, fuel cell systems offer modularity, high efficiency across a wide range of loads, minimal environmental impact and opportunities for use as CHP systems. Stationary fuel cells are ideal for power generation, either connected to the electricity grid to provide supplemental power and backup for critical areas, or installed as a grid independent generator for on-site services.

Since fuel cells operate silently, they reduce noise pollution as well as air pollution and the waste heat from a fuel cell (REFERENCE) can be used to power singular floors of commercial or residential space within a sustainable tall building, and offer the option of hot water and space heating to that particular floor. Combined with a rainwater harvesting system, each floor is supplied with heated running water at an ultra-low cost.

In the stationary power sector, if fuel cell manufacturing costs are reduced to the level expected through volume production, electricity generating costs could eventually be as low as 3- 4p/kWh (excluding any utilisation of heat).

Rainwater harvesting

Rainwater harvesting tanks are usually located on the roof of a tall building, and are used to collect rainwater. The water is then pumped throughout the building to the point of use supplying the building with a source of alternative sustainable water. The water is used for toilets and non drinking water taps. The available water is determined by the tank size and local climate. Thus rainwater harvesting has a limited operational use.

The use of water recycling systems is also of interest to high rise buildings, particularly those of residential use. All toilet, tap and kitchen waste water can be reused in a process called “grey water recycling”.

Biomass Energy:

Biomass Energy is produced by combusting renewable biomass materials such as wood. The carbon dioxide emitted from burning biomass will not increase total atmospheric carbon dioxide if this consumption is done on a sustainable basis (i.e., if in a given period of time, re-growth of biomass takes up as much carbon dioxide as is released from biomass combustion).

Biomass energy can be applied to sustainable tall buildings via the recycling and combustion of waste paper in commercial high rises. This can be aided by the burning of wood and other matter within the biosphere and can aid the self-production of electricity and steam for tall buildings.

Borehole Heat Exchange System (BHE):

For every 100m of depth into the earth's crust the rate of increase of temperature is 2.5-3 degrees C. This renewable energy can be tapped into via a system known as borehole heat exchange.

The heat exchanger refers to the underground pipe network used to reclaim heat from the ground. This piping system is the key to the system's efficiency. Vertical borehole systems are favourable in inner cities where land area is limited and for when the scale of the building is as large such as high rise structures.

A number of boreholes are drilled. Long "hairpin" shaped loops, U-bend pipes, are inserted. They're backfilled, plugged or grouted, and the pipes connected to headers in a trench leading back into the building. The drilling depth is determined by the lowest total cost based on conditions at the job site. Typical borehole depth is 150 to 250 feet. The objective is to install a specific amount of pipe.

Spacing vertical boreholes for residential or commercial high rise systems can be done in a variety of ways lines, squares, rectangles, grids depending on available land areas.

Building Management Systems

The employment of an efficient building management system in a sustainable high rise development is key to achieving optimum sustainability. The building management system controls almost every aspect of the way the building interacts with its physical environment.

The BMS is a computer-based control system installed in the building that controls and monitors the building's mechanical and electrical equipment. A BMS consists of software and hardware; the software program, usually configured in a hierarchical manner.

The system is responsible for controlling, monitoring and optimizing the building's facilities and mechanical and electrical equipment performance. The main aim is to provide a comfortable, safe environment for the user whilst ensuring peak building efficiency of services and sustainable technologies.

These factors in the systems control are:

- Power systems (to provide building with energy)

The computer combines the input of renewable self producing energy provided by sustainable technology (wind, solar, borehole heat exchange etc.) within the building, along with the injection of power needed from the national grid. The computer system automatically responds to power reductions and cuts, and makes decisions about where to source power from reacting in real time, thus resulting in the building operating at peak energy performance.

- Electric Power Control Systems

The system is responsible for control of interior and exterior lighting of plazas and reception/entrance areas. It is also accountable for the control and monitoring of other electrical equipment and systems such as high speed passenger and freight elevators. The system is usually fully automated and able to adjust to different time periods. Although the system is fully automated it can be overridden or set to meet the user's needs.

- HVAC System

All aspects of heating and ventilation are controlled and react to heat and air quality sensors within the building. Often the system is based on climatic changes relevant to the local atmosphere. Internal environment needs to be maintained at a high standard. The system can also control features such as window opening and shading.

- Security and observation system

Safety is always a concern in high rise buildings. If security is compromised at the entrance or reception level of a commercial or residential tall building the consequences could be drastic. The security of high rise structures is paramount following the event of the terrorism acts on the World Trade Centre, New York in 2001. The building management system is responsible for the monitoring and recording of all security observation systems, but must be complimented by a human for this purpose. Although safety is taken into account in a BMS safety system it has little impact on sustainability.

- Magnetic card and access system

Comprises as part of the security system, and allows entry to all authorised personnel or residential users of high rise developments.

- Fire alarm system

Fully automated fire detection and prevention system controlled by the BMS. This includes the programming of phased alarms and evacuation systems. Tall buildings need a refined evacuation procedure that is programmed into the BMS. This way a safe and relatively orderly phased evacuation can take place in the event of a fire, evacuating those at immediate risk first.

The prevention system also includes automated sprinkler systems.

- Plumbing system

All water use and plumbing systems are under the BMS control, including the control of rain water harvesting systems pumping water to point of use.

Intelligent building computer systems can assure sustainable targets are met by managing energy. The system can be controlled within the confines of the building itself or remotely, and most systems are fully autonomous without the need for human interaction. A well designed building management system is a vital to the success of a sustainable tall building.

Energy Performance

Energy performance is recorded by energy companies through the provision of energy bills to the building owners and tenants, but to ensure optimum energy saving performance of a tall building all energy consuming factors and sustainable features performance should be monitored, assessed and recorded by part of the building management system called the building energy management system. This ensures that the data collected can be used to improve the efficiency of the building year upon year, and can aid in the design of proposed new tall buildings.

Sustainable Retrofit of Existing Tall Buildings

Due to the nature of the 21st century and the raised awareness and importance of sustainability in architectural design, an important area of sustainable design is the retrofit of existing tall buildings to improve energy efficiency and sustainability. Given that most buildings have already been built, retrofitting existing buildings could have a far bigger impact than making new developments sustainable.

This is a large challenge due to the scale of tall buildings and the challenges involved in accessing upper areas of the building to retrofit with sustainable equipment and materials.

Retrofit Case studies

Empire State Building

Serious Materials is transforming the 6,500 dual-pane windows of the Empire State Building into super-insulating weatherproof windows.

The plan is that the old double-pane windows will be removed and disassembled by hand, thoroughly cleaned and fitted into new frames. A thin transparent film will then be inserted between the old panes and an inert gas introduced to increase insulation.

The Serious retrofit will reduce energy use by 38% and make the iconic skyscraper more energy efficient than 90% of office buildings. Carbon dioxide reduction of 105,000 metric tons will be realized over 15 years. Annual energy savings of around £2.5 million will result in a retrofit payback time of 3 years.

The technique involves creating a "micro-factory" on the fifth floor that operates after business hours to refurbish and replace windows overnight so the building is ready for use in the morning.

Taipei 101

The world's former tallest building, Taipei 101 aims to become the highest green structure by completing a checklist of clean energy standards. Taipei 101 will spend £1.5 million over the next year to meet 100 criteria to qualify for LEED (Leadership in energy and environmental design) certification.

Taipei 101 plans to work with its 85 office tenants to cut electricity and water use and encourage them to recycle more refuse, andrestaurants would be asked to bring in supplies from as close as possible to reduce transportation. The Taipei 101 has already met 60 of the checklist items, including double-paned windows to retain cool air.

The future green Taipei tower will be a green landmark in Asia, a region with one of the poorest records for eco-friendly building.

Willis Tower

Formerly known as Chicago's Sears Tower, The Willis Tower will undergo a £200 million environmental retrofit starting in 2010 that will add wind turbines, solar panels, roof gardens and equipment replacements that should reduce energy use by as much as 80 percent

All of the building's 16,000 windows are being replaced, which alone could save up to 60 percent of heating energy. Energy-efficient mechanical and lighting systems are being installed, and the building's 104 elevators and 15 escalators, along with its plumbing systems, are being modernized. Also planned is on-site renewable energy. Solar hot water panels would adorn the 90th-story roof, which is already carpeted with an experimental garden, and several varieties of roof-mounted wind turbines will be tested for their performance at those altitudes.

The retrofit was designed by Chicago-based Adrian Smith + Gordon Gill Architecture. The bulk of the work will begin next spring and is expected to complete in roughly five years. The project will create almost 4,000 jobs. The retrofits will save enough electricity to power a Chicago neighborhood of 2,500 homes for a year. Water conservation is projected at 24 million gallons annually. The owners want to earn LEED Platinum, the highest sustainability designation of the U.S. Green Building Council's LEED rating system. A Sustainable Technology Learning Center is planned to educate the more than 1 million visitors to the Willis Tower each year on ways to save energy and money.

Existing Sustainable Tall Buildings

Case Study: The Dynamic Tower; Dubai

The Dynamic Tower, the world's first building in motion, takes the concept of Green buildings to the next level, generating electricity for itself with a possible surplus for other nearby buildings, making it the first skyscraper designed to be entirely powered by wind and sun.

With wind turbines fitted horizontally between each rotating floor, an 80-story building will have up to 79 wind turbine systems, making it a true Green power plant. While traditional vertical wind turbines have environmental and social effects, including the need for roads to build and maintain them plus their noise and obstruction of views, the Dynamic Tower's wind turbines are practically invisible and extremely quiet due to their special shape and the carbon fiber material of which they are composed.

Photovoltaic ink is to be placed on each roof of each rotating floor to produce solar energy. With approximately 20% of each roof exposed to the sun and light, a building with 80 roofs equals the roofing space of 10 similar size buildings.

In addition, natural and recyclable materials including stone, marble, glass and wood are intended for the interior finishing. Further improving the energy efficiency of the Dynamic Tower, insulated glass and structural insulating panels are employed. During construction, energy use is drastically reduced due the pre-fabrication of the buildings in a factory, versus traditional construction methods, which results in a cleaner construction site with limited noise, dust, fumes and waste.

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