[City and State]
Introduction
Structures such as large buildings can create its own unique internal environment that can significantly impact the comfort and health of its occupants. After many years of investigating and studying building infrastructures, engineers and designers have increased their understanding and knowledge on the environmental conditions that exists within the building in relation to its physical properties. For the same reason, a solid background in building physics is an integral part of a building’s design, particularly in this modern era wherein green buildings are the rising trend. Most modern buildings integrate building physics prior to construction for the purpose of reducing energy consumption and carbon emission. However, most of the buildings that are being used today were built long before modern construction methods and building materials were discovered and made available that they have to be retrofitted in order to make them more energy efficient. An example of such building is the Empire State Building. Considered as a second generation skyscraper, the Empire State Building is the most recognizable landmarks that towers above New York’s skyline and is considered as one of the most popular buildings in the world. Built in 1931 by the architectural firm, Shreve, Lamb and Harmon for building owners, John J. Raskob and Pierre S. du Pont, the Empire State Building became the top contender for the highest building race with a record-breaking height of 381 meters with 102 stories. For more than 40 years, the Empire State Building held the record of the world’s tallest until it was surpassed by the One World Trade Center in 1972. Aside from its height, one of the most remarkable and still unbroken feats of the Empire State Building is the speed of its construction. Considered as unprecedented in the history of high-rise building construction, the Empire State Building rose at the rate of four and a half stories per week; the fastest for a project of such scale and enormity. The Empire States Building was completed in just one year and forty-five days, which is three months ahead of schedule . The building costs $24.7 million, which is almost half of the projected cost of $43 million. In terms of speed and efficiency, the project was remarkable. Sacrifices, however, would have to be made in order to meet the owner’s deadline. More than anything else, speed is the major consideration for the building’s design. From conception to completion, the builders designed labor, materials and all other aspects of the building in order to meet the deadline set by the owners. But as the years progress, it became apparent that the Empire State Building would have to be renovated in order to meet the sustainability standards in terms of energy conservation and carbon emission. Energy efficiency of the Empire State Building, however, is a challenging task primarily because the building’s original design does not account for the current green building standards. To address this concerns, the building will have to be retrofitted with new technologies and building materials in order to improve its energy conservation capabilities and reduce its carbon emission.
I. Use of Building Physics in Design of Green Buildings
Physics and structures are interrelated concepts that could not be separated. The existing knowledge in building structures, for instance, depends entirely on the physical characteristics of the materials involved; the structure’s geometry and the forces that acts on them. Building physics, therefore, is not an entirely new concept because it has always been employed by builders consistent with the existing knowledge in structure and material technologies. Building physics is a dynamic concept that evolves over time. As observed by scholars, the science involved in building a structure, especially buildings that are used for dwellings, could not be isolated to the construction process alone, but also to the physical, biological and social sciences that is interrelated with the structure (Carmeliet, Hens, & Vermeir, 2003, 20). Buildings such as skyscrapers have unique physical characteristics that impact their internal environment. Aside from these physical characteristics, there are also environmental factors that influence the internal environment of buildings that must be considered in a building’s design or retrofitting. The building materials used in tropical climate, for example, is different from those that are being used in colder regions. Excessive heat gain, for instance, is a constant problem in buildings that are located in tropical regions than in regions with temperate climate (Ahmad, Ossen, & Chia, n.d., 1). In tropical regions, the building’s material, space, and air conditioning system focuses exclusively on cooling demands. Buildings in temperate climates, on the other hand, must be flexible so it can adjust to the changing climatic conditions. Ideally, buildings on regions with temperate climate should be able to retain heat during winters while provide cooling during summer. Aside from impacts on heating, ventilation and air conditioning (HVAC), climatic conditions also impact the lighting systems of a building. In tropical regions, buildings can take advantage of the intense day light in order to maximize their energy savings while buildings in temperate regions should take into consideration certain times of the year when sunlight is less intense. Apparently, there is a difference in solar radiation with respect to a building’s location in earth’s latitude. Even in a day with clear skies, the length of daylight varies directly with the building’s distance from the equator. These climatic factors are part of the physical forces that subsequently impact the energy consumption and carbon emission of a building. Engineers and designers, therefore, should consider these factors in the design and retrofitting of a building. Such factors were also the major consideration in the retrofitting of the Empire State Building.
Figure 1. The relationship between the length of day with respect to the days of the year (Burgess 2009, 4).
Empire State Building Design
Aside from height prospects, construction speed was the major design consideration of the Empire State Building. For the same reason, it is only logical to think that some compromises, particularly in the building’s energy efficiency and carbon emission, was overlooked or was not given emphasis and importance. The building’s design is generally classified as Art Deco, an architectural style characterized by its emphasis on the vertical or horizontal aspect of a structure, combined with symmetrical and repetitive geometric and rectilinear themes (The Art Deco Movement and Definition n.d., 15). The Art Deco architecture is an obvious choice considering the advantages it offers in terms of design simplicity and building efficiency. This design suits the desire of the builders of the Empire State Building primarily because they can fabricate materials that can be fitted and installed directly to the building. The construction of the Empire State Building was like a huge production line process comparable to the mass production methods during the time. According to observers, “windows, spandrels, steel mullions and stone, all fabricated in various parts of the country, were designed so that they could be duplicated in tremendous quantity and brought into the building and put together almost like an automobile on the assembly line” . Its skeleton steel frame is composed of pre-fabricated steel; each of which is manufactured so it can be hoisted directly to the building’s framework. In a sense, the Empire State Building can be considered as an enormous steel structure clad with limestone, marble, granite and glass materials that serves as its interior and exterior cover. The Empire State Building also features a stepped-back design consistent with New York’s zoning code during the time, which requires that buildings over a certain height should not occupy the same amount of area as its base (The Art Deco Movement and Definition n.d., 16).
Energy Conservation/Low Carbon Emission Design
The Empire State Building was built primarily for commercial office occupancy. Being one of the most popular commercial offices in the world, the Empire State Building’s office spaces are almost fully occupied by tenants. The building, itself, is visited by more than three million guests and tourists annually. As a high-performing building, it requires huge amounts of energy, which also results to high amount of carbon being emitted as a result of the building’s operation. Most traditional buildings experience similar challenges in energy and carbon emission issues, primarily because their amenities are still based on traditional technologies. According to the data gathered by the U.S. Department of Energy, buildings “account for 72 percent of U.S. electricity use and 36 percent of natural gas use”. In the United States, buildings consume more energy as compared to the industrial and transport sector. Most of the energy used in buildings comes from fossil fuel. For the same reason, energy consumption in buildings is also directly equivalent to carbon emission. In the United States, it is estimated that buildings are responsible for 40% of the total greenhouse gas emission (Howe n.d., 7). Lighting and HVAC or short for heating, ventilation and air conditioning are two of the most energy consuming aspects in high-rise buildings with office occupancy. According to a data provided by the U.S. Energy Information Administration, 44% of the energy consumed by commercial buildings is used for HVAC purposes, specifically for space heating (25%), ventilation (10%) and cooling (9%), while 10% is used for its lighting systems. For the same reason, it is only logical to think that any attempts to reduce the building’s energy consumption must first focus on these aspects.
Figure 2. Energy Use in the United States
Figure 3. Average energy consumption of a commercial building.
Lighting Energy Reduction Strategies
One of the major focuses of the Empire State Building’s retrofitting project is to improve energy efficiency by reducing the electrical consumption of its lighting systems. Over the years, the rapid progress in lighting technologies has helped improved the energy efficiency of buildings. Originally, the Empire State Building is lighted by incandescent bulbs that does not only expend a huge amount of energy, but also needs to be replaced often because of their low life span. The incandescent lamps were eventually replaced by fluorescent lamps. These lamps last longer and is significantly more energy efficient compared to incandescent lamps. Today, the LED technology offers a more efficient lighting system for buildings. Apart from changing the building’s lighting fixtures, there are other lighting strategies that can be done simultaneously in order to maximize energy reduction. Two of the most common strategies are utilization of natural light and improving the building’s lighting control system.
Natural Light Utilization Techniques
Over the years, the increased knowledge in structural design as well as the discovery and development of new building materials has allowed for greater freedom in building design. Modern buildings can now maximize energy savings since it is less constrained by structural materials and design limitations as compared to their predecessors. Owing to the development of steel framing design, modern structures such as the Empire State Building can do away with load-bearing wall structures that block the sunlight. A good design that maximizes natural light is key to a more energy efficient building. The Empire State Building, for instance, is designed in such a way that it maximizes the amount of natural light that enters the building. The building’s corridors, restrooms, vertical circulation, shafts and elevators were strategically placed in the central portion of the building while the rentable spaces surround the perimeter where the building’s huge windows are located. Prior to the development of steel framing, such design would be inconceivable. Traditionally, thick load-bearing walls are necessary to carry the weight of a multi-storied building. But with the use of steel materials, the traditional thick, load-bearing walls became unnecessary. As a result, building walls only serves as façades and can be opened to maximize the amount of natural light that reach the interior of the building ( High-Rise Building Definition, Development, and Use 2009, 7). The maximization of natural light offers many advantages. Aside from the energy savings, daylight is also known to improve productivity. As observed by scholars, “Daylight provides a better lighting environment than cool white or energy-efficient fluorescent electrical light sources because daylightmost closely matches the visual response that, through evolution, humans have come to compare with all other light” (Edwards & Torcellini, 2002, 3). The Empire State Building’s natural light utilization can be further increased either by increasing the area of the window as well as improving its placement (U.S. Department of Energy 2012, 14). But unless a major renovation is undertaken, these alternatives may not be feasible as it would drastically alter the building’s façade. Another alternative would be to replace the traditional glasses with glasses that have a high visible light transmittance (U.S. Department of Energy 2012, 16). However, with the building’s 6500 glass windows, this alternative can be costly. A better option would be to maximize the open spaces near the windows by removing partitions within the office space if applicable. Another alternative that improves natural lighting is by painting the interior walls with light colors as well as placing reflective materials such as wall mirrors in order to maximize reflected light.
Lighting Controls
Being able to control the building’s lighting system is also a key component of energy and carbon reduction alternatives. In 2008, the Empire State Building embarked on a massive rehabilitation project, which included the installation of intelligent lighting control systems. With the use of state of the art technologies, the Empire State Building’s operators and tenants achieved better control of their energy consumption. It is projected that the building’s retrofitting of energy saving initiatives would reduce its energy consumption as well as its carbon emission by 38 percent (Rocky Mountain Institute n.d., 2). In the 1970s, before the energy and carbon reduction became a trend, most building operators believes that a brighter building is better than a poorly lit one (Electric Lighting History n.d., 26). However, the rising cost of electricity as well as the desire to conserve energy for ethical reasons made designers and engineers reevaluate the building’s lighting systems. The result of this re-evaluation is to improve lighting efficiency by providing improved controls. Today, designers and engineers emphasizes ‘task lighting,’ which refers to the practice of “putting higher levels of light where needed, such as a desktop, and less light in other areas” (Electric Lighting History n.d., 26). Lighting control systems can be broadly categorized into two; manual and automatic. Traditionally, buildings are installed with manual switches in order for the occupants to manually control the building lights. Today, automatic control is possible with the use of sensors and intelligent control systems. Greater light control can be achieved by enhancing the building’s lamps as well as its automatic control system capabilities. Among the most common lighting control strategies employed in buildings are alternating luminaries, dimming and alternating lamps (U.S. Department of Energy 2012, 21). As seen in the figure below, alternating luminaries allows the occupants to light only half of all the luminaries in a particular area while alternating lamps allow the lighting of alternate lamps within luminaries. Another light control strategy is to create a switch system wherein the occupants of a certain area can control a portion of the luminaries. A significant amount of a building’s light can be automatically turned on and off for better energy conservation. Lights in areas wherein there are no security risks involved as well as exterior building lights, such as parking lots, walkways, canopies and facades can be automatically controlled with respect to time.
Figure 4. Three common types of lighting power reduction strategies (U.S. Department of Energy 2012, 21).
HVAC Energy Reduction Strategies
Maintaining the thermal comfort and the quality of air inside the building is necessary for the health and well-being of the occupants. For the same reason, an efficient HVAC system should not compromise the health of the building’s occupants for energy reduction considerations. There are certain strategies, however, that can be employed in order to improve the energy consumption of HVAC systems without compromising the health and comfort of people inside the building. One of the strategies employed in the Empire State Building as part of its retrofitting project is by retrofitting the existing windows in order to improve its thermal regulating properties. The building’s 6,514 old windows were removed and retrofitted on site. The retrofitting process consists of placing a thin film in-between the original glass panes while the space in between the film and the glass panes was filled with a mixture of inert gas, particularly krypton and argon (Malkin 2015, 365). The retrofitting of the building’s glass window significantly impacted the building’s heating and cooling efficiency since it has better heat retaining properties during the winter while its thermal insulation prevents excessive solar heat gain resulting in a cooler building interior during the summer (Harrington & Carmichael, 2009, 5). Another HVAC energy reduction strategy employed in the building is the installation of radiative barrier behind each radiator unit located below the building’s windows. The logic behind this innovation is to prevent heat from escaping the building through the walls (Harrington & Carmichael, 2009, 5). The building’s HVAC is also embedded into the building’s intelligent monitoring and control system; allowing greater control of the building’s thermal comfort without even pushing a button. Part of this intelligent control system is the Demand Control Ventilation, which features carbon dioxide sensors that monitors the amount of carbon dioxide inside the building and automatically controls the bringing in of outside air into the building.
Figure 5. Retrofit of the Empire State Building’s windows.
Conclusion
Energy and carbon reductions are among the major challenges of today’s buildings. Many existing buildings today, for instance, do not have adequate energy reduction features while some needs a major overhaul in order to improve its energy efficiency. The Empire State Building is one of those traditional buildings whose initial design is constrained by the existing technology when it was constructed. But with the use of modern energy reduction strategies, the building has significantly reduced its energy consumption and consequently its carbon emission. The energy saving strategies used in the Empire State Building can also be applied to other buildings in order to maximize energy cutback. Energy efficient buildings are still a work in progress. Hopefully, with the discovery of new energy saving techniques and building materials, energy and carbon reduction can still be improved.
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