Utilizing Traditional Cooling Techniques in Modern Architecture
Ayushi Gupta (67794)
American University of Sharjah
July 2, 2017
Utilizing Traditional Cooling Techniques in Modern Architecture
Buildings are meant to provide people with a comfortable living and working environment, guarded from the upshots of harsh climate. Before the advent of technology, thermal comfort in buildings was achieved by ingenious natural cooling techniques like cross ventilation, shading and evaporative cooling. However, in recent times, there has been a significant shift from traditional cooling techniques to modern air conditioning methods. Moreover, these modern air conditioning methods are extremely expensive and energy consuming. According to the U.S. Energy Information Administration (2016), \"energy consumed in the buildings sector due to [modern air conditioning] accounts for 20.1% of the total delivered energy consumed worldwide\" (p. 4). They contribute to various environmental problems like ozone layer depletion, carbon dioxide production and global warming. Utilizing traditional cooling techniques in modern architecture can reduce the demand for modern air conditioning methods while maintaining thermal comfort and thus, reduce the environmental impact and overall energy consumption caused by modern air conditioning methods. These traditional cooling strategies are often referred to as \"Passive Cooling\" techniques as they make use of low or no energy to cool the buildings (Gupta, 1981). In addition, they involve natural methods to maintain balanced indoor temperature, with minimum energy consumption. Passive Cooling techniques are harmonious with nature and hence provide a source of inspiration for environment friendly development in the modern world.
Modern Air Conditioning Methods
Air Conditioning is a relatively new technology. It was first developed in 1902 by a young engineer named Will Carrier to prevent paper from wrinkling in the heat and humidity at the Sackett-Wilhelm\'s Lithographing and Publishing Company in Brooklyn, New York (Rosen, 2011). Thereafter, in the 1920s smaller and safer units of air conditioners were developed in the United States (Rosen, 2011). It was only after the World War II that these conditioners became household essentials, with \"more than one million units sold in 1953 in United States\" (Rosen, 2011). Since then there has been a drastic increase in the use of air conditioners over the world. For instance, in China, \"the percentage of households with air conditioner grew from less than 1% in 1990 to exceeding 100% in 2015, i.e. more than one room air conditioner per urban household\" (Dennis & Mooney, 2016, para. 2). Moreover, it has been estimated by the Berkeley Project Reports that, \"the world is poised to install 700 million air conditioners by 2030, and 1.6 billion of them by 2050\" (Dennis & Mooney, 2016, para. 5). In numerous ways, this significant increase in air conditioners is going to be a leading cause of disastrous energy consumption and environmental hazard.
Ozone Layer Depletion
With the increase in global temperature, people are buying air conditioners at an alarming rate. However, modern air conditioning tends to make the environment even hotter with its contribution to the ozone layer depletion and global warming. Most air conditioners use chemicals like Chlorofluorocarbons (CFCs) and Hydrofluorocarbons (HFCs) as their cooling agent (McMullan, 2000). When these agents are released from the air conditioning system, they undergo physical and chemical changes and cause ozone layer depletion. The ozone layer is a layer in the stratosphere containing high concentrations of ozone (O3) that prevents the penetration of harmful ultraviolet radiations into earth\'s atmosphere. However, the increased presence of CFCs and HFCs in the environment due to modern cooling methods has resulted in 65% depletion of this ozone layer over Antarctica, often being referred as the \"Ozone Hole\" (McMullan, 2000). In addition, CFCs have exceptionally long atmospheric life and hence, it is believed that \"they will keep depleting the ozone layer for the next 100 years to come\" (McMullan, 2000, p. 87). Such deterioration of ozone layer will allow large amounts of ultraviolet rays to enter the earth causing skin cancer and cataract amongst animals and human beings.
Modern air conditioning is a leading cause of global warming and climate change. HFC, a cooling agent used in air conditioners, is a potent greenhouse gas and is much stronger than carbon dioxide at absorbing heat (Davis & Gertler, 2015, p. 2). When released in the atmosphere, HFC produces immense carbon which forms an insulating blanket around the earth. Ideally, when heat radiations from the sun arrives on earth, about 30% is reflected back into space (McMullan, 2000). However, due to the presence of greenhouse gases like carbon, HFCs and carbon dioxide, the heat that has to be reflected back gets trapped within the earth\'s atmosphere. Therefore, the temperature at the surface of the earth rises from the temperature it would have been without the insulating blanket of carbon. Consequently, this results in the change of climate at various places. Most of this increase has happened over the course of three decades. It has become a vicious cycle; the increase in the air conditioning has led to an increase in temperature and that has led to a further increase in air conditioners and hence forth.
Apart from the environmental impact, air conditioners consume immense energy in the form of electricity. It is estimated that with more air conditioners at use, \"there will be an a 83% increase in residential electricity consumption by end of the century\" (Davis & Gertler, 2015, p. 3). In addition, numerous countries generate electricity through fossil fuels. This means that rise in air conditioning can lead to \"billions of tons of increased carbon dioxide emissions\" (Davis & Gertler, 2015) and hence, global warming. Moreover, the energy consumption in summers due to air conditioning is even worse. In case of UAE, \"it accounts for a 60 per cent increase in the country\'s energy consumption during the summer months\" (Todorova, 2011, para. 1). Furthermore, such massive amounts of energy consumption is harmful to the environment as well as expensive. According to a recent study by David and Gertler (2015), 46% of the world\'s electricity bill comes from the air conditioning in residential sector.
In recent times, modern air conditioning has become quintessential to maintain comfortable indoor temperature in residential and industrial sectors. However, the increased use of this advanced technology has contributed to various environmental problems like global warming, ozone layer depletion, carbon-dioxide production and increased energy consumption. With the world facing a huge energy and fuel crisis, modern air conditioning is an enormous problem. It is of paramount importance that thermal comfort in buildings is achieved with as little expenditure of energy as possible. It is possible that by utilizing traditional cooling techniques in conjugation with modern air conditioning, the environmental impact and energy consumption caused by modern air conditioning can be reduced.
B. Traditional Cooling Methods
Traditional architecture has evolved over thousands of years to develop various cooling strategies for each type of climate, without using any mechanical or electrical cooling. Incorporating these traditional cooling techniques in a building design can improve the indoor thermal comfort with low energy consumption. It mainly relies on three main principles: reducing the amount of heat entering the building, modifying the heat gain and furthermore, removing the heat that is already present inside the building (Gupta, 1981).
Reduce Heat Gain
It is of paramount importance to minimize the heat entering a building in order to improve the effectiveness of traditional cooling techniques. It requires the complete or partial exclusion of heat radiation from building surfaces or surrounding spaces (Panchabikesan, Vellaisamy, & Ramalingam, 2017). It can be achieved through the following techniques:
Insulation is a method to reduce heat gain in buildings. The more a building is insulated, the less is the heat transferred into the building. In some traditional buildings like the Mehrangarh Fort, situated in India, the entire roof surface was covered with small closely placed inverted earthen pots (Vijayalaxmi & Sekar, 2013). The pots were usually made out of mud clay obtained after digging more than ten feet deeper into the earth and were often placed in an inverted position (Bainbridge, 2011). The air trapped inside these empty pots acted as a poor conductor of heat and hence, reduced the amount of heat entering into the building. Although this technique was thermally efficient, it suffered from practical difficulties as the roof was rendered unusable and difficult to maintain. However, in a recent development, this ancient technique has been modified and altered in order to make it more efficient and implementable. Today, it is known as the \"Burnt Pot Roof Insulation\" or the BPRI (Sarma, 2009). According to Sarma (2009), a renowned Bangladeshi architect and inventor of BPRI:
BPRI, first applied to the roof of a two storied house in Khulna city, Bangladesh, in April, 2002, is an extremely effective way to reduce heat gain. In this system, burnt clay pots or simply the earthen pots are placed in inverted positions and are covered with a thin layer of Lime, Surki and Building Rubbish. This additional layer makes the roof accessible and the air trapped inside acts as an insulator and hence helps in heat gain control. Furthermore, the pots are covered with polythene sheet to protect against the leakage of humidity or water. This system is extremely cost efficient and effective in cooling. BPRI costs only 10% of the usual roofing system and itâ€™s weight per unit area is about 50% of the conventional roof weight per unit area. (p. 3)
It has been recorded that the use of BPRI at Khulna house has brought down the cooling loads by about 30% and has also reduced its temperature by 7 degree Celsius in comparison to the exterior temperature (Sarma, 2009). BPRI, inspired from traditional cooling techniques, is highly efficient in reducing heat gain and thus cooling the building with nil energy consumption. However, the use of this technique is limited to areas with available clay.
There are many approaches in which a building can be shaded. In traditional courtyard buildings in the Mediterranean region, a toldo or fabric shade was covered over a courtyard during the hot summers (Bainbridge, 2011). These shades were often made of fabric that were open weave or translucent. They admitted enough sunlight so that the porch was not dull and dim but also kept the porch and the building much cooler by reducing the amount of heat entering the building. According to John Reynolds (2002), a prominent architect at New Orleans, United States, this technique of shading courtyards and porches can reduce the building temperature by more than 2 degree Celsius. In modern architecture, motorized or mechanical overhang can be used as an alternative to provide sun when wanted and shade when needed. Moreover, it can include a mix of louvres, shade screen, shade cloth, or crisscrossed wood strips to shade the courtyards and porches in order to reduce the heat gain in a building (Bainbridge, 2011). This traditional technique can cool the buildings with low or nil energy consumption.
2 Modifying Heat Gain
Heat in a building can be usually modified by absorbing it during the day and using it at night to provide warmth. The mass of a building, typically contained in walls, floors, partitions, is usually constructed with materials of low conductivity that absorb most of the heat during the day; hence, cooling the building (Madhumathi & Sundarraja, 2014). During the night time, when the outer temperature is lower, the mass of the building emits the absorbed heat into the environment; therefore, maintaining the thermal comfort (Madhumathi & Sundarraja, 2014). Traditional buildings like Amer Fort in India, have thick walls which are designed to provide thermal insulation and security. The material used in Amer Fort is mud in form of cob (Gupta, 1985). The term cob is most accurately used to describe â€œa wall system made of a mixture of clay, soil, sand, and straw, sculpted in place while wetâ€ ( Evans et al., 2002, p.12). Generally, their thickness varies between 8 inches and 3 feet and is most commonly used to support the weight of the roof that rests on them ( Evans et al., 2002). An example of such existing ancient architecture is the Hawa Mahal in India. It uses large thermal mass structures coupled with night ventilation to reduce itâ€™s interior temperature by 30% (Endurthy, 2011). Today most of the buildings in Bikaner, India are constructed using the same technique to reduce the cooling load. According to a recent study by Jakhar and Mathur (2009), this technique has reduced the internal temperature by 10 degree Celsius in Bikaner.
3 Removing Internal Heat
Another method to cool the building is to reduce the heat that is already present in the building. It involves techniques like evaporative cooling, natural ventilation and ground cooling.
a Evaporative Cooling
Evaporating water has a powerful cooling effect. The state of the water changes from liquid to vapor, releasing immense energy and hence, cooling the surface. Many traditional buildings used this type of cooling by creating pools or fountains in the courtyards or gardens or by sprinkling the tile or floor with water. In traditional Iranian buildings, running water was placed in ventilation towers, known as \"badgirs\", in order to improve the air flow in the building (Bainbridge, 2011). The badgir is a traditional wind tower used for cooling of buildings with nil energy consumption. The function of this tower is to â€œcatch cooler breeze that prevail at a higher level above the ground and to direct it into the interior of the buildingsâ€ (Bahadori, 1985, p. 121). The air moving through the tower is then redirected over a pool of water and is further cooled by evaporation. After this point, the air is channeled into the building to reduce the temperature of the building. Although, this technique is effective in cooling a building, it is impractical in modern architecture as the wind tower requires a significant height in order to function. However, The Environmental Research lab at the University of Arizona has developed a modern version of this wind tower that is compatible with modern buildings. It includes evaporative pads, wetted curtains and clay pipes (Chalfoun, 2002). They use a pad or set of evaporative pads at the top of the tower. The intake air is then cooled by these evaporative pads and further allowed to fall down the tower through clay pipes and into the building (Chalfoun, 2002). The inclusion of the evaporative pads has resulted in the decrease of the size of the tower significantly. A test system of this tower installed on a home has provided good thermal comfort, never exceeding 26 degree Celsius inside, despite exterior temperature reaching 42 degree Celsius (Chalfoun, 2002). Therefore, modern wind towers can be easily incorporated in new buildings due to their small size and can hence, reduce the temperature of building with natural means and nil energy consumption.
b Natural Ventilation
Natural ventilation is an important traditional cooling technique. It results from the differential wind forces acting on the various building surfaces and from the temperature difference between the exterior and interior of the building (Bansal, 2014). Furthermore, factors such as â€œsurrounding landscape, location of other buildings, the building form, orientation with respect to wind direction, size and proportion of window openings and arrangement of internal partitions also affect the rate of ventilation within the buildingâ€ (Bansal, 2014, p. 209). In many traditional Islamic buildings in India, natural ventilation was used by installing a small window on a large wall that allowed the wind to move inside the building with a greater force and velocity (Ali, 2013). In addition, traditional lattice screen with smaller sections was also installed in order to further increase the velocity of the entering air (Ali, 2013). This technique is still quite prevalent in modern architecture in India and is based on the principle termed as Venturi Effect. According to this principle, when air with a greater velocity enters a building, it undergoes a sudden expansion that results in the lowering down of the temperature of the building (Bansal, 2014). Therefore, it reduces the internal temperature of the building with almost no energy consumption. One of the unique examples of natural ventilation is a modern building is the Panchmahal at Fatehpur Sikri, India. This five story pavilion is an asymmetrical building diminishing from bottom to top and covered with small windows and lattice screens, cooling the building by close to 40% of the cooling provided by modern air conditioning methods (Ali, 2013). Today, Nath Maljiâ€™s Haveli, Jaisalmer, India incorporates the same technique of natural ventilation and the effect is such that the family does not even feel the necessity to install air conditioners in the rooms (Gupta, 1985).
Benefits of Traditional Cooling Techniques
Most of the traditional cooling techniques discussed before are extremely simple and easy to install. They are usually cost efficient and low maintenance. In addition, these techniques are sustainable and help maintain a healthy indoor air quality.
The building sector in tropical countries is an intensive energy consuming sector, mainly due to the cooling requirements needed for maintaining indoor thermal comfort. Furthermore, the modern air conditioning methods used for this purpose are discordant with nature and are a leading cause for ozone layer depletion, global warming and energy consumption. Modern air conditioning techniques cannot be eliminated completely but further research can resolve at a better understanding of the aforementioned techniques and their utilization in modern architecture. As discussed in this paper, the application of traditional cooling techniques in combination with modern air conditioning methods can provide thermal comfort, with low energy consumption. Moreover, a recent study by Majumdar (2002) has shown that utilization of traditional cooling techniques can reduce the energy consumption by almost 70%. Therefore, it is essential for architects and building engineers to incorporate traditional cooling strategies in order to build sustainable and environment friendly buildings. Almost all of the adverse impacts of modern air conditioning can be avoided by good design and construction influenced by traditional architecture. As Fathy (1986), noted Egyptian architect and engineer, said, \"the principles that produced the traditional solutions must be respected. This is the only way modern architecture can surpass, in human and ecological quality, the achievement of vernacular architecture\" (p. 69).
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