Energy Efficient Architecture and Building Systems to Address Global Warming
Publication: Leadership and Management in Engineering
Volume 8, Issue 3
Abstract
Our planet is warming because of human activities affecting the environment. Climate change is caused by a number of things, and it will take an enormous amount of concerted effort to fix it. It involves thinkers, politicians, professionals, and the public. Architects and engineers will have a major role to play in resolving the associated problems. This paper explores various architectural and building technologies that are employed to achieve a low-energy built environment. The paper concludes that designers of the next generation of buildings, whether residential, commercial, or institutional, should aim for “zero energy” buildings in which there will be no need to draw energy from a region’s power grid. In this approach, climate and environment are used to advantage rather than being treated as adversaries and buildings become sources of energy, like batteries. A few illustrative buildings are discussed that represent the new generation of sustainable or green buildings.
Although it has been known for some time, in his documentary film An Inconvenient Truth, former Vice President Al Gore has brought home the point to the masses that the global weather system is warming up. It sig-nals that more energy will be squandered throughout our planet, and hence more wind storms and precipitations are on the horizon. There is another ominous danger, which is the uncertainty about the security of the fossil fuels that will be required to drive the world economy in the foreseeable future. As demand increasingly exceeds supply, oil prices will rise. At least half the oil reserves will be located in the volatile Middle East and there is a growing demand in developing countries like China and India that are industrializing and are large consumers of energy.
According to a February 2007 report by the U.N.’s Intergovernmental Panel on Climate Change, “warming of the climate system is unequivocal” and human activities have played a significant role by “overloading the atmosphere with carbon dioxide hence retaining solar heat that would otherwise radiate away” (Kluger 2007). Human interference in the form of releasing massive quantities of into the Earth’s atmosphere has already begun to disturb the equilibrium of the natural carbon cycle. The principal human activity that causes this imbalance of the carbon cycle is the burning of the fossil fuels, which adds mammoth quantities of carbon to the environment. A few other gases together with (collectively called greenhouse gases) form a layer over the Earth causing some heat from the solar radiation to be trapped in the atmosphere. The long-wave radiation is reflected by the Earth’s surface upward through the atmosphere and then reflected back to Earth once again by trace gases in the cooler upper atmosphere, resulting in additional warming of the Earth. In addition to , other pollutants such as sulfur dioxide , nitrous oxides , carbon monoxide , and particulates are emitted from the burning of most fuels including fossil fuels. On top of the environmental impacts, the supply of fossil fuels is limited and is being depleted rapidly. Levels of in the atmosphere were 379 parts per million (ppm) in 2005, higher than at any time in the past 650,000 years. And of the twelve warmest years on record, eleven took place between 1995 and 2006. Also, global in 2006 approached 32 billion tons, with about 25 percent originating from the United States (Kluger 2007).
Whereas 30 percent of the world population lived in urban areas in 1950, the proportion of urban dwellers climbed to 47 percent in 2000 and is projected to rise to 60 percent by 2030. It is projected that by 2030, five billion people will live in urban areas throughout the world (United Nations 2001). Energy shortage, global warming, urban sprawl, air pollution, overflowing landfills, water shortage, disease, and global conflict will be the legacy of the twenty-first century unless we move quickly toward 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 Development
We hear much talk about “sustainable development.” Sustainable development is employed to express policies that balance people’s needs today against the resources that will be required in the future. For a sustainable community, a strategy that considers sociocultural, economic, and environmental resources both in the short and long term must be adopted. Sustainability also implies using renewable natural resources in such a way that they are neither eliminated nor degraded, or their usefulness is not diminished in the future. In practical terms, sustainable development means such things as destroying forests no faster than they can grow back, using groundwater no faster than restoration by precipitation, using renewable energy sources rather than exhaustible fossil fuels, and farming in such a way that soil quality does not undergo degradation. Moreover, economic considerations must be given to account for environmental costs as well as capital, labor, raw materials, and energy costs.
In broad terms, the main goal of sustainable development is to find the highest level of interaction among the three systems: the biological resources system, the economic system, and the sociocultural system. The concept of sustainable development or sustainability did not come so much from academic discourse as from an international political process emphasizing the environment around the human habitat and its future (Newman 2001). At the 1972 UN Conference on the Human Environment the notion of sustainability was brought up on a global scale. One hundred and thirteen nations pledged at the conference to begin cleaning up the environment and tackling the environmental issues on an international scale. The oil embargo of 1973 precipitated the crisis of energy shortage and acted as a strong impetus to do something about energy conservation.
In 1983, the UN established the World Commission on Environment and Development in an attempt to resolve the conflicts arising out of the aspirations of the developed and developing worlds. The term “sustainable development” was first introduced in the 1970s by G.H. Brundtland (also known as the Brundtland Commission) and in 1989 the World Commission on Environment and Development (WCED) published “Our Common Future” or the Brundtland Report (WCED 1989), which formally launched the expression “sustainable development,” and was reinforced in 1992 at the Earth Summit in Rio. Sustainability was projected as an agenda to solve the global environmental problems and to facilitate the economic development of the underprivileged nations. In other words, the idea of protecting the environment morphed from a political to an economic agenda during the two decades between 1972 and 1992.
The following four characteristics were derived from the Brundtland Report (Newman 2001):
1.
The elimination of poverty, especially in the Third World, is necessary not just on human grounds but as an environmental issue. Thus Third World economic and social development is a precursor to global sustainability.
2.
The First World must reduce its consumption of resources and production of wastes. That is, first world economic and social development are precursors to global sustainability, but in the future they must be much less resource-intensive.
3.
Global cooperation on environmental issues is no longer a soft option. Thus a global orientation is a precursor to understanding sustainability.
4.
Change toward sustainability can only occur with community-based approaches that take local cultures seriously. Therefore, an orientation to local cultures and community development is a precursor to implementing sustainability.
Sustainability or sustainable development has generally been defined on the basis of the Brundtland Report, and may be defined as “the development that meets the needs of the present without compromising the ability of future generations to meet their own needs” (WCED 1989).
Green Design Concepts
Different categories of principles have been developed to guide sustainability efforts frequently specializing in one area, such as built form design, energy management, etc. The popular interpretation of the expression “green design” for buildings based on the ongoing so-called “green movement” on a global level describes an approach to design that minimizes sustenance or resource consumption so as to prolong the availability of natural resources. The terms “sustainable” or “green” do not express the minimization of the expenditure of those resources that are necessary for the prolongation of life. Rather, they define the fact that no humanly created environment can survive without the contributions of the larger natural environment or ecological systems. Sustainable design is thus a response to awareness and not a prescriptive formula for survival.
To many architects and engineers, sustainability is generally related to developing a built form that is sensitive to the environment, is energy conscious, promotes the conservation of natural resources, and promotes the recycled use of synthetic materials. This environmentally conscious design is but one facet of sustainable design that has emerged from the 1960s with the advent of solar panels and visionary creations, such as Paolo Soleri’s Arcology (Arcidi 1990), and the consciousness of the ecosystems of the 1970s. The essence of green buildings can be described as “solar, passive, ecological, sustainable, regenerative, or just plain green—environmentally aligned approaches to architecture are guided by both scientific principles and a worshipful romance with nature. Consequently, green buildings are part method, part philosophy, and part ethic” (Bachman 2003).
Another factor of green design is the humble submission to nature or at least a proactive cooperation with the inevitable natural forces. Similarities exist in their use of minimalist resources and ethic of efficiency. The differences are more defining. First, there is a differentiation in what each would treat as optimal levels of technology. “For High Tech (a mode of architecture in which the building services are revealed and emphasized) the goal is unfettered expression—design may be visually minimalist but is sometimes exaggerated by exuberance. Green buildings, on the other hand, use restrained technologies that satisfy function and work within a regulated cycle of flows while producing the lowest ecological impact” (Bachman 2003).
Green technology embraces local materials, site-specific conditions, and complex interactions between occupant, architecture, site, and climate. Sustainability is a clarion call for the adoption of a new way of thinking and acting responsibly toward the surrounding environment and the creation of new environments. In addition to its environmental and ecological associations, sustainability has assumed a broader meaning in terms of communities and cities. Sustainability is essentially an endeavor to apply scientific, engineering, and economic knowledge to assist in rectifying the negative consequences that the unrestricted application of technology helped create. The explosive population growth throughout the world coupled with dramatic changes in technology and energy-intensive growth of developed countries increases the possibility of permanent damage to global environment. Design professionals involved in the shaping of the built environment that accommodates thousands of people in a city must, therefore, consider such concerns seriously. The question then arises: How do we design for a sustainable future?
The question concerns not the design professions alone, but also the industry. The corporate world now is actively seeking to understand the environmental consequences of current human activities and attempting to figure out what their impact might be if their businesses were aiming for sustainability. A built environment that is ecologically responsive will unquestionably alter the way we live and work. Among the many environmental impacts of buildings, energy consumption is one, and is perhaps the most significant. Except for the most renewable energy systems, the energy consumed in operating our built forms carries very significant ecological impacts at each stage of resource extraction, usage, and waste disposal.
Green Building Rating System
There are many green rating systems. The Leadership in Energy and Environmental Design (LEED) developed by the U.S. Green Building Council (USGBC) has become the standard by which all sustainable buildings are designed and rated. It has five goals: (1) sustainable sites; (2) water efficiency; (3) energy and atmosphere; (4) materials and resources; and (5) indoor environmental quality. Innovation and design process is included as an additional category. It addresses the energy issue in the third goal. Under energy and atmosphere (EA), buildings aspiring to achieve LEED certification are required to meet three perquisites and six energy credits. EA prerequisite 1, for example, dealing with fundamental commissioning of the building energy systems, requires the following systems to be commissioned:
1.
Heating, ventilation, air conditioning, and refrigeration (HVAC&R) systems and associated controls;
2.
Lighting and daylighting controls;
3.
Domestic hot water systems; and
4.
Renewable energy systems.
Some important considerations under this goal are well-insulated building envelopes, high-performance windows and glazing, daylight harvesting, etc. These are reflected in the credits. For example, to obtain EA credit 1 (optimize energy performance), the building must incorporate on-site renewable energy systems.
While the LEED rating system offers a checklist for green commercial and institutional buildings, it is not adequate for residential construction and does not explicitly cover all aspects of green design that would yield an ecological built form that would address architectural and structural practice, ecological impact, infrastructure systems, and community development.
Energy Efficiency in Tall Building Design
Tall buildings in major cities will be with us in the future until viable alternatives are found and they must be designed as humanely habitable and as sustainable as possible. Skyscrapers in city centers are massive consumers of energy and release large amounts of greenhouse gases in the built environment. During much of the twentieth century, the typical model for a tall building in America was rectilinear with central air-conditioning—that is, the “box”—which was exported to major world cities without regard for either the impact on environment or the local climatic and cultural requirements (Wood 2005). The invention of mechanical air conditioning by Willis Carrier in America in 1939 and its widespread use in the post-war years had a profound effect on building design in the latter half of the twentieth century. Fully glazed and sealed curtain walls allowed in more light, but also increased the solar gain, which had to be offset by the cooling system. By ignoring the external climate, engineers, architects, and their clients also ignored important differences in regional conditions, endlessly reproducing the familiar standardized tower form (i.e., the “glass box”). More energy conscious European cities, however, realized the importance of green design and produced examples of tall building design that are in sync with their natural surroundings and are focused on energy conservation with both mechanical and appropriate façade treatment strategies.
Energy consumption by elevators is significantly high as the cost of operating and maintaining them is also high. Because of the construction of many supertall buildings, elevator technology has been a topic of continuous research and development. Significant improvements have been made in this technology to make the elevators safe and the mode of travel efficient and comfortable. A new system of destination-oriented elevators has recently been introduced by the industry that allows people to log in their destination at a central lobby kiosk and group people together going to the same floor of a multistory building, thus reducing travel time. This reduces the number of elevators and saves energy, thereby reducing cost and opening up additional floor area for renting or other use.
Environmental awareness extends to both the urban environment and the context in which a tall building is placed as well as its interior environment. The issues of indoor and outdoor air quality and microclimate, and the potential toxicity of materials and chemicals used in building components, systems, and furnishings are also of concern to the building users. Designing a sustainable building, therefore, requires a 360-degree view of the entire building enterprise—that is, consideration of the local and global environment, the availability of renewable and nonrenewable resources, community impact assessment, and the collaborative input of architects, planners, engineers, social scientists, behavioral scientists, and other community-based groups.
Use of Alternative Energy Options
With the present methods of production and the fuel mix, electricity is highly energy inefficient. The primary energy contained in the natural state of fuel is only partly exploited at the point of use (i.e., the delivered energy is only 30 percent efficient). It can be hardly overemphasized that we must recognize the benefits of bioclimatic design in terms of emissions and providing high-quality indoor environment. The relative emissions among different forms of fossil-based energy are as shown in Table 1 (Smith 2001).Table 1. Carbon Dioxide Emissions
| Fuel | Kg/KWh delivered |
|---|---|
| Electricity | 0.75 |
| Coal | 0.31 |
| Fuel oil | 0.28 |
| Gas | 0.21 |
Combined Heat and Power
A highly efficient technology for energy saving in densely built-up urban areas is the combined heat and power (CHP) system. In Europe, this is an increasingly popular system for servicing commercial and institutional buildings. CHP is the simultaneous production of power, heat, and occasionally, chilled water for air-conditioning, and is also known as co- or tri-generation. CHP avoids transmission losses as electricity is generated close to the point of use. The simultaneous production of electricity and heat in a useable form enables overall thermal efficiencies, meaning significantly less fuel is used for a given amount of work. The result is a net cost saving and reduction of 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. The widespread use of CHP is common in many European cities. Stockholm, Helsinki, and Copenhagen, for example, provide much of their electricity and heating from CHP systems. A typical distribution of total energy output from a CHP system is shown in Table 2 (Smith 2001). CHP is thus an attractive option since most of the energy is useful and it can be adapted to low-to zero-carbon applications. It is a flexible system.Table 2. Energy Output Distribution of CHP System
| Source | Percentage |
|---|---|
| Electricity | 25 |
| High-grade heat | 55 |
| Medium-grade heat | 10 |
| Low-grade heat | 10 |
Solar Energy and Photovoltaics
There are two categories of solar energy: passive and active. Passive solar energy is put into practice as a design strategy to accomplish direct or indirect space heating, daylighting, etc. Active solar energy is implemented through technical installations such as solar collectors and photovoltaic (PV) panels. There are two basic types of solar collectors: flat bed collectors and vacuum tube collectors. PV is an advanced technology and practical solution for the sustainable supply of energy in buildings. PV cells convert light into electrical energy. Electricity is produced when photons or particles of light are absorbed by semiconductors. PVs were invented in the mid-twentieth century and have recently been developed as a viable “building integrated” PV system. According to the International Energy Agency (IEA), most solar cells in current use are manufactured from solid-state semiconducting material. The average annual growth rate of PV modules has been at 30 percent in recent years (IEA 2003). Commercial PV cell performance has been steadily increasing depending upon the type of cell and PV cell density to allow
The Menara Mesiniaga of 1992 in Subang, Malaysia, designed by T. R. Hamzah and Yeang, presents an early model building for the physical translation of ecological principles into high-rise architecture (Yeang 1996). Both the external and internal design features use a bioclimatic approach to produce an operationally low energy building that makes the most of the pleasant ambient tropical climate. The fifteen-story tower expresses its technological innovations on its exterior and uses as little energy as possible in the production and running of the building. Instead of a continuous façade, the building open and closes in sections arranged in stages around the tower. The interior and exterior structure of the tower is planned around climatic considerations and its orientation toward the daily path of the sun. The massive core of the building, with elevator shafts and staircases, faces east and screens off the penetrating heat up to mid-day. Deep incisions and suspended aluminum sunscreens on the south façade ward off the direct rays of the noon and afternoon sun into the interior.
Several factors determine the efficiency of PVs in a particular location. These are:
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Orientation;
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Compact developments with more or less consistent roof heights are ideal for roof-mounted PVs; and
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Open urban space may utilize the potential of façade PVs. Seasonal changes in the sun’s angle that influence overshadowing must be taken into account.
The application of PV technology for tall buildings can be significant since they provide an opportunity for a clear path of direct sunlight by towering over other buildings. The disadvantage of PV technology is the large amount of electricity required in its production, the source of which is fossil-based fuels. Also, stringent management and recycling assessments are required for the toxic and inflammable gases like phosphate and cadmium in its production. Intense research is continuing in this area to overcome these difficulties. The Law Courts Building in Los Angeles is a recent
The Commerzbank of 1997 in Frankfurt, Germany, was the first high-rise in the world with natural ventilation air-conditioning and natural lighting in compliance with German building regulations in which “all office spaces have daylight and visual contact with the outside world” (Lepik 2004). It is triangular in plan rising and topped with a high mast. Three wings of deep office space surround a central atrium at whose corners are located the structural columns with the transport, supply, and waste disposal facilities. Offices are contained in two wings suspended between the columns, with a garden on the third side. Nine winter gardens spiral upward and ensure an adequate supply of daylight to the inner workplaces. An intelligent air-conditioning system allows the natural ventilation of all the office space by means of slits between the inner and outer façades up to the highest floors. Through the recovery of heat and other innovative technology, energy consumption is greatly reduced in comparison with traditional high-rise buildings.
Because of the higher initial cost of PVs some governments, notably Germany, the United States, and Japan, have intervened to enable PVs to achieve economy with subsidies. In conjunction with subsidies, market growth and technical gains are likely to yield dramatic reductions in cost. A large amount of production would bring PV prices down to the level of conventional power. The key to success will be to produce PV-integrated roof and wall systems that will compete with conventional materials and products.
Wind Energy
A renewable energy source is wind, which can be advantageously tapped at higher altitudes of tall buildings where wind speed is considerably large. As for the PVs for solar energy, wind turbines can be installed on buildings to produce electricity. Taller buildings can be shaped to funnel wind into a zone containing wind turbines without having negative effects on the structure, its surroundings, and the occupants. By such profiling of the structure, wind speed can be amplified and produce more energy.
Costs of wind energy have dropped, reliability has increased, and wind power now competes well with some conventional power-generating technologies. Wind energy can be efficiently harvested for tall or massive buildings. For individual homes, the technology is better suited to utility scale power production necessitated by the economies of scale. Windmills have moving parts that warrant specialized maintenance. Therefore, it is beneficial to combine multiple windmills in one location on wind farms so that they can be maintained economically. One disadvantage of wind turbines is that they, together with other moving mechanical components, may cause vibration on a slender structure. For the proposed . Freedom Tower design at the New York World Trade Center site, the initial employment of wind turbines at the top was eliminated subsequently for this reason. This may be, however, suitable for concrete buildings where vibrations will be low because of the relatively large mass and higher damping characteristics of concrete. Another disadvantage is the noise created by the rotating turbines and other moving parts.
Fuel Cells
Fuel cells are electromagnetic devices that generate electricity like batteries and can be considered as electrochemical internal combustion engines. A fuel cell is essentially a reactor that combines hydrogen and oxygen to produce electricity, heat, and water. At this time its cost is high but with future mass production it is bound to go down. Fuel cells are used in spacecrafts and airplanes. Now they are being used in buildings such as in the Conde Nast Building in New York City. In the near future fuel cells will provide heat and electricity for many offices and residences.
Fuel cells are clean, quiet, and efficient with few moving parts. They are classified by their type of electrolyte (Smith 2007). One of the most common kinds of fuel cell is the proton exchange membrane fuel cell (PEMFC). Some other types are phosphoric acid fuel cell (PAFC), solid oxide fuel cell (SOFC), alkaline fuel cell (AFC), and molten carbonate fuel cell (MCFC). The U.S. Department of Energy plans to power two to four million households with hydrogen fuel cells by 2010 and ten million households by 2030. A fuel cell depends on renewable energy and will warrant an efficient electricity storage system. This remains a challenge at present. It has great potential as a carbon neutral energy source of the future.
Bioenergy
Biomass is the sum total of all the Earth’s living matter within the biosphere. More specifically, it refers to the concept of growing plants as a source of energy. The energy reaching the planet is equivalent to about seven times its primary energy expenditure. When biomass is converted to a fuel as a store of chemical energy the process is more or less carbon neutral—that is, the carbon emitted when it is burnt equals the carbon absorbed during growth. However, there is
Foster & Partners developed new technological, urban planning, and ecological design concepts in the high Swiss Reinsurance Headquarters Building in London. The steel spiral “diagrid” strupture creates an aerodynamic form that provides the lowest resistance to wind (Riley and Nordenson 2003). The shape of the building also diminishes demands on the load-bearing structure, as well as the danger of strong katabatic (downward) winds in the area around the building. The office spaces are arranged around a central core with elevators, side rooms, and fire escapes. The office space is divided into six parts and separated from one another by triangular voids. The uniqueness of the design lies in the twist of successive floors by five degrees, so that the voids stacked up form a helical atrium space through the building. The most innovative element in the inner structure is the inclusion of triangular light shafts behind the facade, which spiral upwards over the whole height of the building. These light and air shafts are interrupted every six stories by an intermediate floor to minimize the development of drafts and noise.
Biomass fuel such as waste paper can be used for generating electricity and steam for high-rise buildings. A 73-story multiuse high-rise project was investigated by Alfred Swenson and Pao-Chi Chang of the Illinois Institute of Technology in this regard (Ali and Armstrong 1995). Substantial amounts of biomass are ubiquitous in tall office buildings in the form of paper, most of which is used only briefly and trashed. The estimated compacted waste paper for a large office building in Chicago was found to average per day in 1991. Based on these data, Swenson and Chang assumed a waste paper production of per day for offices and commercial space for their study. It was concluded that the waste paper output would produce about one half of the system fuel required. Another conclusion was that a biomass-integrated gasifier/steam injected gas turbine (BIG/STIG) would be the most efficient system for using biomass fuel. The use of gas turbines with biomass fuels was investigated at the Princeton Center for Energy and Environmental Studies (Larson and Williams 1990). Biomass energy generation does not contribute to global wanning since it is essentially carbon neutral, as previously noted.
Geothermal Energy
Geothermal energy is one of our most plentiful resources. The “geothermal gradient” (i.e., the rate of increase of temperature according to depth in the ground), averages 36.5 to (2.5 to ) per . of depth. Modern drilling techniques can penetrate up to about 6 miles . The most common surface manifestation of geothermal energy is simply hot water from springs. Natural hot water has been used since the nineteenth century for industrial, applications. The first geothermal power station was built in 1913 and produced (Smith 2001). Another source is the high-temperature dry rock. The geothermal heat has to be brought to the surface. Water is pumped through boreholes and returned to the surface to provide space heating—a process known as borehole heat exchange (BHE). An advantage of geothermal energy is that it is independent of seasonal variations and climate changes.
A significant area of innovation is the pairing of geothermal energy with heat pump technology. This technology has incrementally been improved, especially in the United States. During the last five years, the number of geothermal ground-source heat pumps has grown by 59 percent with most of the development in the United States and Europe (Smith 2007). Development and refinement of technology in general are necessary to make geothermal energy economically competitive with conventional sources of energy. Its application to tall building design could prove to be more relevant than for any other building type.
Building Management Systems
Innovative building technologies such as computer-based smart or intelligent building systems can play a major role in managing energy usage. The increasing reliance on computer technology and automated systems can be directed toward achieving a sustainable functioning of skyscrapers. The building management system (BMS) is a centralized control system to manage the operations of the various building systems such as fire protection, security, communication networks, elevators, HVAC systems, etc. The environmental data collection and control system is usually incorporated within the BMS and can also be used to control more passive features like opening windows and shading devices. The component of the BMS that deals with energy-related services is controlled by the Building Energy Management System (BEMS), also known as the Energy Management and Control System (EMCS), which may in some circumstances function autonomously. The control system need not be located on-site and the supervision of the system can be cen-
The Conde Nast Building in New York City is the first sustainable North American skyscraper (Howeler 2003). The large areas of glass curtain wall maximize daylight penetration into the office floors and incorporate low-E glass coating to filter out unwanted ultraviolet light while minimizing heat gain and loss. Photovoltaic panels have been integrated in spandrel areas on upper floors of the east and south façades, generating a nominal but symbolic amount of electricity by day. Sophisticated mechanical systems ensure high indoor air quality by introducing filtered fresh air into the office environment. Tenant guidelines produced by the architects established environmental standards for living, power usage, furniture systems, carpets, fabrics, finishes, and maintenance materials to ensure indoor air quality and also as a comprehensive strategy to maintain environmental sustainability for the life of the building.
Integration of building services with the structural and envelope systems is highly desirable in sustainable buildings. Although this has been a trend for recent buildings, more research is needed in this area. Lessons can be learned from other industries such as the aircraft and automobile industries, which aim for maximum performance in conjunction with maximum possible energy savings.
Assessment and Analysis of Energy Performance
Although a building may be designed to be sustainable and energy efficient, actual performance in this regard needs to be assessed and verified. Computer software packages for assessment methods are developed and constantly upgraded to offer designers a tool for determining the energy performance and lifecycle costs for the buildings they design. Extensive research is needed to monitor and measure the performance of sustainable buildings that were recently built. While this seems to be a straightforward task that may merely involve collection of data on year-round energy usage on a global scale for a building, the challenge lies in finding out the relative energy consumption for different systems, such as mechanical and HVAC, lighting, computing, elevators, etc. The utility companies keep track of the total energy consumed and not the energy consumed by each system or subsystem in a building. Being aware of the breakdown of energy demand of a building in terms of its systems will enable designers to design the building in a more efficient manner. Another area of research will be the development of strategies for making recently built buildings sustainable. This obviously is a much bigger challenge since it involves remodeling and reconstruction.
A principal reason why Europeans are leading the way in sustainable design is the fact that legislation in some European countries requires the building owners to take on a more responsible attitude to energy consumption. Energy costs are higher in Europe than in the United States, encouraging the reduction in life cycle costs of a building and making expensive initial cost systems viable investments. Germany has also made an enormous contribution to sustainability by building a few remarkable towers based on sustainable principles, such as the Commerzbank Tower in Frankfurt and RWE Headquarters in Essen. In Asia, Malaysia has led the way by applying the bioclimatic design principles suitable for tropical climate (Yeang 1996). Thorough analysis of site and its environment is fundamental to the design of a climate-sensitive skyscraper. The analysis should range from the general macroclimatic characteristics of the region, including solar radiation, wind, air temperature, and humidity data to the more site-specific conditions at the microclimatic level. Such analysis should also include the effects of shadows, the topography, vegetation, adjacent buildings, and the availability of daylight.
Ecological Design
Ecological design considers the building’s effects on the natural environment in its entirety. Ecological design’s essential characteristic is the interrelationship between all human-made and natural activities. One aspect of ecological design is called bioclimatic design, which was pioneered by Ken Yeang. This utilizes the energies of the local climate (Yeang 1996). The National Commercial Bank of 1982 in Jeddah, Saudi Arabia, is an early example of ecologically designed building.
Energy Efficient Building Envelope
Daylighting and shading are usually the key aspects to envelope design for typical green buildings. The façade of a building covers the bulk of the exterior surface area and in tall buildings over 90 to 95 percent of the external surface area—that is, the roof area in tall buildings is almost insignificant compared to façade areas. Thus, the energy gain or loss for a high-rise building depends very much upon the materiality and technology employed in the façade treatment. Facades not only offer the building’s aesthetic expression, but it can also be advantageously used to control the internal conditions of the building since it represents the building’s envelope or “skin.”
Curtain wall systems have a long history of development to their present form. Starting at the end of World War II, the twentieth century’s metal and glass curtain wall systems
The Solaire is a twenty-seven story luxury apartment building located on the Hudson River in the Battery Park City of New York and the first residential green building in the world (Beedle et al. 2007). Solaire employs photovoltaics, half of the on the façade and the other half on the roof. Sensors controls and high-efficiency fixtures in the Solaire resulted in 70 percent more efficient lighting than a standard building. The building also features wastewater and storm water reuse systems and other water conservation strategies. Solaire’s daily operation is carried out by the Building Management System (BMS), which controls HVAC, fire, lighting, security, and other systems. The building is a remarkable example of sustainable architecture and design in which technology is applied for system integration.
The glazed facades popularly used for tall buildings have both positive and negative effects on energy consumption. There has been recent success in reducing the negative effects through innovative techniques. 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). The penalty suffered in increased embodied energy of the materials involved to improve the thermal insulating properties of facades is often paid back in reduced energy consumption over the life of the building. Air-tightness of the façade is a major issue for green tall buildings where pressure differentials from higher winds at the top of a building can cause problems with controlling internal temperatures and drafts. Double skin facades also help reduce wind speeds that occur when opening a window, and act as a buffer to outside noise as well. These facades can be set up to provide ventilation that is either continuous or controlled. For continuous ventilation, a continuous connection is maintained between the surrounding environment and an air gap enclosed by the outer skin. This air gap has a constant air supply and an exhaust opening that remains always open. In case of controlled ventilation, openings in ventilation systems can be regulated by dampers that allow a modification of the temperatures within the air gap.
Double-skin facades are classified into three different types (Katz 2002). In Type 1, the double wall is not vented in winter and the heat is trapped and transmitted to the interior. In summer the cavity is vented and air circulates, cooling the cavity. This wall type requires interior doors for access to the cavity for cleaning and maintenance. In Type 2, the wall is inactive, creating a low U-value, with a continuous volume of dry air pumped through the cavity to prevent condensation. Because the cavity is sealed, low maintenance is required. In Type 3, internal mechanical heating and cooling are installed with the double wall and it utilizes cool and warm water to control cavity temperature and adjust for exterior atmosphere. This type of wall is the costliest of the three. Type 2 is the most economical because of low maintenance demands and fewer operable parts.
Double-skin facades act as buffer zones between internal and external conditions, reducing heat loss in winter and heat gain in summer. In combination with ventilation of the space between the skins, the passive thermal effects can be utilized advantageously. Natural ventilation can be drawn from the buffer zone into the building’s interior by opening windows on the inner skin. The stack effect of thermal air currents in tall buildings offers advantages over buildings of lower height. This eliminates potential safety and security problems caused by having windows opened at the elevated heights of the building as well as wind pressure differentials around the building. This type of double-skin glazed façade used in the HSBC Headquarters Building in London has contributed to a 20 percent reduction in energy costs.
There is a definite relationship between façade and the installation of PVs. The available surface area for the façade or roof PV installation is primarily determined by the surface-to-volume ratio of the building. A high ratio implies potential for facade-integrated PVs. In a high-density area, overshadowing will limit this potential. A lower surface-to-volume ratio on the other hand suggests potential for roof PVs. The spacing between buildings is an important factor in ascertaining façade PV opportunities. The next generation of PVs will most likely have thin films that will integrate better with the façade. Ideally, the façade itself will probably have the dual function of an enclosure-come-PV.
Daylighting and Electric Lighting
Daylight design that relies on the type and size of glazing can help reduce considerable energy requirements for inter-
“Eco-functional” design is a concept developed by Bill Dunster (Pank et al. 2002). His most prestigious project is the Beddington Zero Energy Development in Sutton, London. He has produced an advanced design for a tower known as Flower Tower whose footprint consists of interlocking petals that meet in a space in which a vertical axis wind turbine is installed. While this design was mainly for housing development, it could be suited as well for a mixed development of office block. It is a highly insulated building and has a wind turbine and PV panels on the roof and the walls. It is an advanced ecological housing project that is largely self-sufficient in energy.
In high-rise buildings, lighting can account for 10 to 25 percent of the overall electrical load depending upon the small power requirements and the amount of heat load going from lighting back into the cooling load (Raman 2001). Including energy-efficient lighting is crucial in buildings, where optimized solutions can result in a substantial savings. Lights have a relatively low embedded energy cost and therefore the energy savings are real. Energy-efficient lamps and lighting control systems can be integrated with daylight to provide reductions in overall consumption. The best advantage can be gained from automatic control of electric lighting as a function of ambient daylight levels.
There is a fine balance between maximizing glazing in the façade of a building to harness daylight and minimizing the heat transmission properties that influence thermal comfort conditions and heating/cooling loads. According to many researchers, adopting façade systems having a maximum glazed area of 50 percent should be a practical limit. Ken Shuttleworth, who has designed remarkable tall buildings such as the abundantly glazed Swiss Re Tower in London while employed at Foster and Partners, believes that façade design is on the front line of a change (Shuttleworth 2005). He used 50 percent glazing for the Kite Tower that he designed.
To manage sunlight appropriately, innovative window systems have been developed that include elements that both maximize and minimize light. External solar shading can be added to lower sections of windows, while higher sections may reflect sunlight on to the ceiling plane. Different types of glass and applicable films are also available to enhance the performance of lighting in the workspace.
Aiming for High-performance Building Systems
There is hardly any doubt that global warming will initiate changes that will fundamentally change the building design and construction practice. It is anticipated that global warming will lead to greater frequency and intensity of storms, hurricanes, and floods. As heat is built up within the biosphere, more energy is released that results in extreme climate changes. Structural engineers must therefore be prepared to design buildings subjected to progressively increasing wind loads and higher intensity of buffeting. Another consequence is the increase in extreme heat waves. This will affect the way HVAC systems for buildings are designed now. Rainfall and drought patterns will change across the globe. This will increase the demand for water conservation and harvesting of both rainwater and grey water and influence the properties of soil and hence the design of foundations and substructure. Increased sea level will cause flooding and will necessitate the construction of flood-resistant buildings.
Buildings in use or under construction are the greatest single indirect source of carbon emissions accounting for 50 percent of total emissions. The future of the built environment depends on the methods and techniques used by engineers in collaboration with the architects to design sustainable, intelligent buildings. Engineers owe this to society and must take a leadership role when they design future buildings. The initial cost of green buildings may be 5 to 10 percent higher than that of a conventional building, but the long-term lower operational cost makes it justifiable. If one understands that it is possible to make the environment and climate work for the building rather than the building working against it through the use of innovative technology in building design, one can go a long way in achieving zero-energy buildings. The ultimate aim is to create buildings with zero net-energy use in which new technologies can be employed to avoid using any energy from the city’s power grid. Each building could be designed as a source for generating energy. Not only can the energy consumption be lowered—but taking it to the next level, the building could be a power source of its own. A zero-energy building may be achieved through high-performance design, integrated physical systems, a symbiotic building within its context, and an interactive power grid with the building’s energy
Pearl River Tower in Guangzhou, China (under construction at the time of this writing) is an example of a building that aims for a net energy footprint of zero by relying on special features such as on-site wind turbines and recovery and recycling of condensed water. The conceptual idea of this skyscraper design was to generate even more energy than it consumes. The building is shaped to harvest wind energy and oriented to maximize possible solar gain. It has notches or scoops on the façades from the bottom to the top that allow the wind turbines to function better and generate more energy by accentuating the wind speed. Its design also uses the double-wall system, fuel cells, solar collectors, and geothermal heating and cooling, etc. It also uses an innovative floor slab to ensure continuous air movement and allowing light for all spaces.
References
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Biographies
Mir M. Ali is a professor in and chair of the Structures Program in the School of Architecture and the University of Illinois Urbana-Champaign.
Information & Authors
Information
Published In
Leadership and Management in Engineering
Volume 8 • Issue 3 • July 2008
Pages: 113 - 123
Copyright
© 2008 ASCE.
History
Published online: Jul 1, 2008
Published in print: Jul 2008
ASCE Technical Topics:
- Architectural engineering
- Architecture
- Building design
- Building systems
- Buildings
- Climate change
- Climates
- Design (by type)
- Energy efficiency
- Energy engineering
- Engineering fundamentals
- Environmental engineering
- Global warming
- Green buildings
- Structural engineering
- Structural systems
- Structures (by type)
- Systems engineering
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