History of Passive Solar Energy

Scott Barber East Carolina University Faculty Mentor: Michael Behm East Carolina University ABSTRACT Passive solar design, an idea within the growing trend of green building, is a creative way to use the sun to our advantage, both for heating and cooling, based on the design of buildings. As green building has continued to become more popular, many changes have been made to make the design and construction of our buildings more environmentally and economically sustainable. This review focuses on the development in passive solar applications, from its earliest appearances in ancient Greek buildings to current designs that take advantage of radiation convection or acrylic panels. There have been many passive solar developments that can be explored, and the innovative technol- ogy today has brought about great advancements in the past few decades alone. This review presents a compilation of information from a variety of sources that provide knowledge regarding the his- tory of passive solar energy. As the popularity of green building continues to grow, it is essential to develop an understanding of passive solar design, and other green building techniques, in order to be equipped for the years to come.

and natural gas. This type of deterioration assive solar systems are used to is not only evident in natural gas, but P “collect, store and distribute thermal also in many other common sources of energy by natural radiation, conduction energy. Though many are aware of the and convection through sophisticated decreasing amount of oil, most people design and wise selection of building assume there is an endless supply of coal, [9] materials” . This definition, provided nuclear, and other energy sources. It has by J.K. Paul, sufficiently explains that been estimated that there is enough coal the idea of passive solar energy is the use to last about 250 more years[14], enough of natural processes, such as radiation, oil to last approximately 44 years[5], and conduction, and convection, to distribute nuclear fuel to last 23 years[12], if the cost thermal heat provided by the sun. Passive is kept somewhat higher. Even if these solar energy also involves blocking the sun’s numbers are a low estimate, and enough rays in order to provide cooling during the energy sources remain for several more summer. Incorporating solar energy into centuries, there is still a need to find cleaner our buildings will decrease the amount sources of energy. What many people are of money we spend on energy as well as unaware of is the damage that our current extend the time other sources of energy energy sources cause to the environment[4]. will last. The pollution and other byproducts of Due to increasing oil prices, rising gas manufacturing usable energy from these prices have become a common sight not raw materials have dramatically affected not only in the United States, but around the only the atmospheric quality, but they have world. The exploitation and misuse of our also damaged the surrounding ecosystems, natural resources is rapidly depleting our oil

2 Scott Barber whether they are forests, prairielands, or manner. It is also helpful to understand water habitats. Ron Jones, an architectural specific savings in cost for buildings that expert for sustainable building, explains use passive solar energy. According to a that humans have begun to further explore document provided by Appalachian State and understand the relationship between University, a passive solar home could the built environment and the natural save as much as $160 per year by using environment. In the past, we simply were simply using movable insulation and low- concerned about the effect of nature on emissivity glass, glass that radiates low buildings, but now are realizing the impact levels of radiant thermal energy 11]. our buildings have on the environment. In this paper, I overview the history This is the key to sustainable design[6]. of passive solar design as well as review There is a plethora of renewable and analyze technological information energy sources that provide energy that is regarding the use of solar energy. The much better for the environment. While goal of this review is to inform the reader the mining and burning of coal and of historical passive solar energy uses and uranium leads to smog, acid rain, and air to explain in greater detail what passive toxins, renewable energy, including solar, solar energy is and how it is applied. wind, hydropower, geothermal, or even renewable materials such as agricultural CATEGORIZATION OF PASSIVE products or biomass, results in little, if SYSTEMS any, pollution. These types of renewable sources are becoming a pivotal aspect of the To have a better understanding of increasingly popular “green” movement. passive solar energy, it is helpful to know There are three parts of being green: being how to categorize passive systems used for acceptable economically, ecologically, and this type of solar energy. While there are socially. These three pillars make up the specific techniques and systems that use the sustainability movement, and help direct sun’s energy in a passive way, they are all decisions so that processes and materials defined as being either direct gain, indirect used are suitable in each of these areas. For gain, or isolated gain. example, when installing wind turbines, Direct gain is the simplest application of to completely fit within sustainability, one passive solar energy, where the space of the must take into consideration these three building is directly heated by the sunlight, ideas to ensure that the turbines will be which most often enters through windows economically efficient, environmentally within the south-facing wall for buildings in friendly, and socially acceptable. While a the northern hemisphere[7]. Ideally, in this wide variety of renewable sources exist, approach, the materials within that space they are not developed enough currently ought to be capable of storing heat and to provide materials and systems that the air flow throughout the room should are beneficial within the three pillars distribute the heat. A representation of of sustainability. However, one type of direct gain is shown in Figure 1, which also renewable energy does have the necessary depicts the difference of the angle of the progress to be used and still be considered sun during the summer and winter, and sustainable: passive solar energy. While how an overhang can be incorporated into many people are aware of active solar the building design for further temperature energy systems, such as solar panels, passive control. solar energy is a division of solar energy that uses the sun’s energy in a more natural

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and temperature regulation. Isolated gain, depicted in Figure 3, uses solar collection and thermal storage that are separate from the actual living space, moving heat to the living space through natural or forced convection. Ventilation is also essential in this method of passive solar heat gain. An advantage to isolated gain systems is that they can be added to new and existing buildings[2].

Fig. 1. Direct gain passive solar energy.

For indirect gain, sunlight is most often received by a south-facing wall, and as air moves throughout the internal space, the heat will then be transferred from the wall to the living space[7]. For increased control of indoor temperature, ventilation at the top and bottom of the wall or other thermal mass is included, assisting in regulating the temperature. Figure 2 clearly displays Fig. 3. Isolated gain passive solar energy. indirect gain, the use of a thermal mass for solar heat gain, as well as vents integrated Regardless of the type of heat gain into the thermal mass for air circulation utilized, passive solar energy provides heat and heat distribution. at little to no cost, aside from the slight variations in the design and construction of the building.

HISTORICAL APPEARANCES OF PASSIVE SOLAR

Solar power has benefited civilizations for centuries, and the knowledge from our past provides foundational understanding of the sun’s energy to bring about our current understanding of solar power. The earliest known application of solar energy arose during the 15th century B.C. by the Egyptian ruler Amenkotep III, who “supposedly possessed ‘sounding statues’ that operated when the air in their Fig. 2. Indirect passive solar energy. base pedestals expanded after exposure Thermal wall with ventilation for airflow to sunlight”[3]. Though this was merely

4 Scott Barber an accomplishment of aesthetic value, Code commenced “sun rights” in order to solar energy has also been used to distill guarantee everyone would have access to water as well as dehydrate agricultural the sun. The last known use of solar energy plants. Solar energy has been used in even before the 1700s appears in North America. more advanced, practical ways by many The Anasazi Native Americans built their civilizations to provide heat for homes, homes in the side of the cliffs in what is light fires, and even cauterize wounds. In now known as the Colorado Plateau, where the 5th century A.D., Socrates realized that Utah, Colorado, Arizona, and New Mexico “in houses that look toward the south, the meet[9]. These south-facing buildings were sun penetrates the portico in winter, while placed within the side of the cliff to avoid in summer the path of the sun is right over the sun in the summer, but make use of our heads and above the roof so that there is the sun during the winter. It is clear that shade”[8], and that initiated the use of solar there was an early understanding of using energy to heat homes. the sun for energy, and this knowledge Though the first recorded application of and technology surrounding it increased solar energy is in the 15th century B.C., the significantly beginning in the seventeenth next appearance wasn’t for several hundred century. years, where the historian, Plutarch, Up to that point in history, through the documented that virgins used cone-shaped 1200s, passive solar energy was used by metal objects to start ritual fires during the Egyptians, Greeks, Persians, Hindus, and 7th and 8th centuries B.C.[3]. During this the Native Americans, following ancient time the sun was used to distill water and architectural teachings of Aristotle, dehydrate agricultural plants. A famous Xenophon, and Vitruvius [9]. In the ancient use of solar energy, while the event is still historical appearances of passive solar surrounded with reservations and disbelief, energy uses, the architecture was geared occurred in 212 B.C., when Archimedes used towards using the sun and wind to alleviate a “burning mirror” to set invading Roman the extremes of the climate, but due to a lack ships on fire. A similar story was recorded of glass, they were unable to utilize the sun in the 12th century, where Proclus, a Greek, to the extent we can today. However, though supposedly accomplished this achievement most ancient civilizations lacked glass and during the siege of Constantinople when other technology that we use today, they the Bitellius fleet was invading, using many still made significant progress and provided mirrors. understanding and a good foundation for While there is no sure way to know whether future developments regarding the use of or not these feats happened, the recording of solar energy. this event sparked much curiosity, and soon Beginning in the 17th century, interest more applications of the sun’s energy were grew in regards to using the sun as an being recorded in history. For example, in energy source, and though there was not a 77 A.D. Romans used “burning glasses” to large amount of development within passive cauterize wounds and light fires[3]. Another solar techniques, significant progress was one of the earliest applications of passive made in active solar systems. The increased solar energy was in the Roman atrium and awareness of solar energy brought about heated bathhouses in the first through the by the experimentation with solar energy fourth centuries, where large south facing served also to make people conscious of the windows let in the sun’s warmth to heat the use of solar energy passively, as well, though pool[9]. Solar energy became so well-known there isn’t as much historical recording of in the 6th century A.D., that the Justinian passive solar energy during this time. In

5 Explorations | Biology and Biotechnology regards to active solar energy systems, the It was in the late 19th century that passive first “solar engine” was invented in 1615 by solar energy began appearing more often Salomon de Caux. This engine used glass and in more noteworthy means. In 1880, lenses to heat up an airtight metal vessel theories surrounding solar houses began to with water and air to produce a small water appear, and it was in Salem, Massachusetts fountain[3]. Though this lacked practical that the idea of a glazed, south-facing wall, use, it is significant because it was the first as well as incorporating the requirements published documentation of solar energy for air flow between the glazing and the after the fall of the Roman Empire. Also wall first arose. Not only that, but professor in the 17th century, physicist Athanasius E.L. Morse was approved for a patent “for Kirchas experimented with starting fire the combination of a dark colored massive with mirrors, and German mathematician wall, an air space, glazing…and adjustable Tschirnhaus worked with lens-type items dampers by which the flow of air could be to concentrate solar energy to melt various controlled”[9]. materials[3]. Overall, the 17th century A few years later, in 1896, the included various experiments from thermosyphon water heater was invented, different specialists who sought practical the oldest and most widely used passive applications of solar energy. solar device in the world, which was utilized In the 18th century, there was more in World War I in Southern California experimentation from many various to provide hot water to army camps[9]. professionals around the world. French Many other southern states adopted this scientist George Buffon worked to technology, as well as Japan and Australia, determine whether or not the Archimedean but the extension of natural gas lines and feat could have been accomplished, the cheap availability of electricity resulted and determined that setting ships on in a nearly complete elimination of its use. fire was possible, but not very probable However, due to increased prices in other considering the lack of technology in energy sources for providing hot water, this 212 B.C.[3]. Another Frenchman, Claude device and its “active but similar offspring," Poillet, provided significant information and the forced circulation solar water that would assist in the development and heater, are beginning to be used more[9]. application of both active and passive These new developments provided more solar energy. He determined the intensity information, but also created specific of the sun in reference to the geographical ways that passive solar energy could be position, and it is this association which implemented into people’s daily lives. For has been regarded “at least as important in example, a home built in Massachusetts solar utilization as the hardware itself ”[3]. was one of the greatest steps in passive It was in 1767, just a few decades later, solar design during the last few centuries, that the first solar collector was invented, providing a concrete and successful use of built by Horace de Saussure, a Swiss passive solar energy. Overall, the 1800s scientist. This collector was used to heat provided more research in solar energy than food, and was used by Sir John Herschel in perhaps any other time in history. However, the 1830s, during his expedition in South the following centuries resulted in a greater Africa[13]. There continued to be a variety diversification of the applications and uses of research and investigation in regards to of solar energy. solar energy during this time, all providing more information that would serve useful in years to come.

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MODERN DEVELOPMENTS In various adaptations and improvements that were made to these designs, double Since the twentieth century, there has glazing, windows that could be opened, been a great variety of fairly modern and ventilating fans were used to maintain passive solar developments. Though the comfort. Unfortunately, there was a deliberate practice of using solar energy slight break in research and development for heating within buildings was apparently concerning solar energy during World War forgotten outside of agricultural, the II, even though there were still companies 1930s reintroduced this practice in the practicing these methods. relatively colder climate of Minnesota[1]. After World War II, despite the revival The sudden increase in the application of interest regarding solar heating, most of and interest in passive solar energy people were focused more on active was a result of sealed, insulating windows systems for solar energy and therefore becoming available at a much more passive solar heating was largely neglected. reasonable cost. Due to the necessity of The American Society of Heating, windows within the application of many Refrigeration, and Air-Conditioning passive solar techniques, easily available Engineers (ASHRAE), however, continued windows allowed passive solar methods to research the gain of solar heat through to appear in residential architecture just window placement, which has provided before World War II[9]. The Keck brothers foundational information for today’s in Chicago were forerunners within the strategies for determining solar heat gain new appearances of passive solar energy, through windows, and has resulted in providing prefabricated buildings in the multiple direct gain passive solar houses in 1940s. These buildings used large, south- New Mexico[9]. facing windows with overhangs to admit These homes implemented newer sunshine in the winter but block it in the technology which improved them summer months. They also included flat significantly from their fairly inefficient roofs that were made to be flooded during predecessors built in the 1930s and 1940s. the summer to decrease the amount of For example fairly consistent temperatures solar heat gain[9]. were gained through concrete or adobe Though these and similar houses were floors which absorb heat. Also, movable being designed and constructed, they insulation protected the house in times of lacked the full potential and were less exceptionally cold weather or when there effective, mainly because the common were extended days where clouds blocked heating and cooling systems were readily the sun[9]. The improvements in these available at a much lower cost. Another structures significantly increased their notable progression within solar energy practicality and effectiveness. use in homes was the book entitled Your In the decades following, there were Solar House, funded by Libbey-Owens- continued discoveries and inventions Ford Glass Company. This book included regarding solar energy. In 1954 photovoltaic forty-eight designs for homes to utilize technology was first revealed, as Daryl direct gain solar energy, one design for Chapin, Calvin Fuller, and Gerald Pearson each state within the United States at that invented the first solar cell that converted time[9]. Again, these designs were not ideal energy from the sun to provide electrical applications of solar energy, primarily power. The following year, Western because there was no consistent way to Electric began selling licenses for silicon control temperature within the buildings. photovoltaic technologies. It was during

7 Explorations | Biology and Biotechnology this time that architect Frank Bridgers monitoring, and rewarding sustainable designed the first commercial office building. In 1985, Austin Energy, located building that used solar water heating and in Austin, Texas, was the first residential other passive solar designs[13]. It is worth energy efficiency program[6]. In 1991, this noting that these passive solar systems are organization further developed and became still in operation within this building today, known as Austin Energy Green Building®. and this office building has been recognized Since that time, many more programs in the National Historic Register as the have begun, such as the Advanced Energy world’s first solar heated office building. Corporation located in Raleigh, NC, the Since these improvements, the most Southface Energy Institute in Atlanta, noteworthy addition to passive solar GA, and the Solar Living Institute in energy is the Trombe wall. Developed by Hopland, CA. In 1995, the United States Frenchman Felix Trombe, based on the Environmental Protection Agency began work of Edward Morse in the 1880s, this the Energy Star program, which evaluates wall faces the sun and essentially absorbs the energy use and efficiency of buildings. the sun’s heat and releases it inside the Since the Energy Star program is limited to building at night[9]. Aside from slight energy, the United States Green Building alterations, most passive solar techniques Council (USGBC) was founded in 1993 and have remained the same and have only within that, the Leadership in Energy and varied in regards to application. Figure 4 Environmental Design (LEED) program shows a modified Trombe wall that utilizes was founded in 1998[6]. These programs a glazing material to collect solar heat and have proved a key role in encouraging and vents to provide air flow and distribute the rewarding sustainable design, including heat to the interior room. This type of passive solar energy practices. Trombe wall is a very efficient way to take advantage of passive solar energy. PASSIVE SOLAR APPROACHES

Although there are many different aspects of passive solar energy as well as the three pillars for producing sustainable passive solar energy, there are five basic approaches to forming these types of passive systems: direct gain, thermal storage walls, solar greenhouses, roof ponds, or convection loops. These techniques can be either direct gain, indirect gain, or isolated gain, based on how they collect, store, and transmit thermal energy [9]. These methods are a result of the extensive research and advancements throughout many centuries, bringing us to the understanding we have Fig. 4. Modified Trombe wall using today, allowing us to use the sun’s energy exterior glazing and air vents for air flow. efficiently and responsibly. Direct gain is the simplest application of A noteworthy aspect of passive passive solar energy, and as such is the most solar design is the many programs and popular. Direct gain is beneficial because it organizations devoted to encouraging, is not only simple, but it also has a relatively

8 Scott Barber low cost. However, direct gain struggles could serve beneficial for both heating because it cannot control temperature and cooling by adding or removing the as effectively due to of a lack of thermal insulation during summer and winter, or storage. Other potential problems that may day and night. arise include undesirable lighting during The final approach for passive solar the day such as glares, as well as discoloring techniques is the convective loop, which uses of fabrics due to extensive ultraviolet a thermo siphon, a machine that circulates rays[2]. water, to move heat from the collection The second common approach to passive point to a storage area. Water heaters often solar energy involves using a thermal storage use this idea, as it is very inexpensive and wall, which essentially uses a material that reliable, more so than many other types absorbs the sun’s heat after it has passed of water heaters commonly known. This through the glazing. The wall may be system works well without needing pumps black or another dark color to assist in its or controls[9]. Air convention loops often absorbing, or it may even consist of water combine passive collection/storage with held in masonry or other containers[2]. active distribution to provide a simple but Regardless of the absorbing material, its effective system to provide temperature purpose is to absorb the temperature and control for a building. release it into the interior room. This assists Overall, these five types of applications of in controlling temperature and reducing passive solar energy can be very beneficial temperature extremes, as well as reducing to include in many different climates and the negative effects of direct gain: glare or situations. When applying these ideas to undesirable lighting and material damage buildings, it is important to be aware of the due to the ultraviolet light. While direct strengths and weaknesses of each of these gain can heat up a room much quicker, it applications. It also may be very feasible to is much more difficult to control, which is combine a variety of these approaches in a benefit of using a thermal storage wall. order to utilize their strengths and develop Often, windows are included in this wall a well-rounded passive solar building. to combine direct gain with the thermal The majority of all passive solar energy storage to incorporate the benefits of techniques are applied during the planning both[7]. and construction process of the buildings, Using a roof pond is the third common because the most important aspect of approach to passive solar techniques[2]. a building is its location and direction. It may or may not include the physical However, there are a few options that presence of water on the roof, but where provide heating from solar energy for there is not water present, movable pre-existing buildings. By adding larger insulation is required on the roof. windows or double-glazed, low-emittance Essentially, this technique relies on windows on the south wall, passive solar gathering solar heat through the roof, but energy can be utilized. The double-glazed, with insulation that prevents too much heat low-emittance windows have the ability from collecting during the hotter summer to allow heat to enter into the building months [2]. There have also been studies but reduce the amount of heat lost to the and research in New Mexico and Arizona, outside. Also, planting deciduous trees, testing various active and passive systems trees that shed their leaves in the winter, to control the amount of heat transferred on the south side of a home will provide through the roof. This type of system shade from the sun during the summer but would be used for a flat roof, ideally, and allow the sunlight to enter into the windows

9 Explorations | Biology and Biotechnology during the winter. Blocking in windows on solar for heating or cooling. However, the north side of a home may also assist in pairing up passive solar aspects with a solar heating, though doing so may not be back-up heating system, shading devices aesthetically pleasing. or operable windows will greatly increase the amount of control one has in regards PASSIVE SOLAR ENERGY: IS IT to temperature[2]. Also, passive solar WORTH IT? heating also maintains a warmer floor, which is desirable. Most heating systems While passive solar energy is growing in used today can lead to large floor-to- popularity within the green movement and ceiling temperature differences, resulting has improved significantly in the last few in discomfort at the floor level. On the decades, there are still doubts surrounding contrary, passive solar systems use materials its viability and effectiveness. The primary that absorb heat, and therefore the floor is arguments that are made in favor of using warmer and more comfortable[2]. passive solar energy are divided into One of the greatest attractions of passive economic, architectural, and comfort/ solar energy is the fact that it is very health categories. In general, passive environmentally friendly; it is a renewable solar energy is very beneficial because it is energy source and does no damage to the inexpensive and has little, if any, impact on environment around it[6]. By using passive the environment. solar energy rather than a common heating When observing the economic aspects or cooling system, there is a great reduction of passive solar design, it is important to in the consumption of fossil fuels and the remember that each building is different, production greenhouse gases and other depending on construction and materials pollutants[6]. Overall, passive solar energy used. However, the benefit to passive solar has few disadvantages and its advantages energy, as opposed to active solar energy are both economical and environmentally or other types of renewable sources, is friendly. that it requires no additional cost for upkeep; the costs are the same as the FUTURE TRENDS general maintenance costs of any building. It is possible to save money long-term While there has been a dramatic amount simply by taking passive solar systems into of progress and development throughout consideration for the design process[6]. history regarding passive solar energy, by Changing the direction of the structure observing where technology is today, one alone, in order to gain more heat from the can only wonder how much more progress sun on the southern part of the building, can be made. While there certainly will be can make a huge difference in collecting improvements in materials, it appears that solar heat. Essentially, passive solar energy the techniques have currently reached a only requires a slight increase in cost, if any plateau. However, when asked “What is it increase at all, to incorporate these systems that we really require from scientists and into the design and construction of the technologists?” economist E.F. Schumacher building. provided guidance into the improvements In terms of temperature within the of passive solar energy: “We need methods building, some people may be hesitant and equipment which have the following to use this technology, mainly because it characteristics: they are cheap enough isn’t easy to control the temperature of so that they are accessible to virtually a room which is dependent on passive everyone, they are suitable for small scale

10 Scott Barber applications, they are compatible with With this in mind, passive solar practices man’s need for creativity, and they are not within sustainable design will become more heavily dependent on natural resources”[10]. common, and industry leaders around the Passive solar energy certainly has the world will incorporate sustainable practices. potential for meeting these requirements. It is important for the future of passive The design of passive solar buildings, solar design that those involved in the based on the materials and technologies design and construction of buildings to be available today, will remain consistent for certified in sustainable design, for resources the next several decades. The strategies and products used to be sustainable, and and techniques being used today will be as a result, the structures will be more replicated in various ways depending on sustainable as well. location and availability to maximize the benefits of passive solar energy. One can CONCLUSION assume that when new technologies arrive, the design of passive solar buildings will Throughout history, mankind has adapt to incorporate them to maximize benefited from and worked to harness their efficiency. However, the specific the sun’s energy in order to create a more design for buildings regarding passive solar enjoyable living space and save energy. Solar energy has climaxed for the present time. energy has been used for centuries and has The further development of passive solar only improved with time, as researchers energy is reliant on new technologies and and scientists have developed processes the development of more appropriate, and materials to improve the quality and efficient resources. One of the newest effectiveness of solar energy. Using solar developments that will continue to grow and energy, specifically passive solar energy, is a improve passive solar use involves window very cost efficient way to take steps towards glazing. Low-emittance coatings, known as sustainability, and as the green movement low-E coatings, are metallic oxide films that continues to develop and expand, passive are installed on windows to reduce from solar techniques will be utilized more and within the building while still allowing solar more throughout the United States and heat gain. These coatings do not affect the in nations around the world. It is helpful visual aesthetics of the window, yet provide to realize the history in regards to passive valuable benefits. There are also double- solar energy, and the benefits that can be glazed windows filled with argon gas, which gained by applying passive solar energy. provide the same benefits as the coatings on Overall, the various types of passive the windows and can be used together to solar energy have unique strengths and increase efficiency. As these technologies weaknesses. Direct gain, the simplest continue to improve, passive solar energy application of passive solar energy, provides will become more beneficial and effective. quick, economically friendly, inexpensive It is also important, however, to recognize heating for a home. The main disadvantage the role that green building programs will is its difficulty in providing adequate control serve in the continuation and expansion of the environment. Indirect gain, a slightly of passive solar practices. Certifications more complicated use of passive solar and recognition within these programs energy, goes beyond direct gain and offers are available for the buildings being a more stable environment with better heat constructed, the professionals who design, control. However, indirect gain requires build, and remodel those buildings, and the greater planning and also takes longer products used for the buildings as well[6]. to heat up a room or home. The third

11 Explorations | Biology and Biotechnology application, isolated gain, delivers even passive solar energy requires an evaluation more control and stability in controlling for each building in regards to feasibility the indoor environment. This, too, requires and usefulness. They can certainly be further planning and is more expensive to useful in many applications, and are worth construct. considering in the planning process. The five strategies used for passive solar Passive solar energy will continue to energy, direct gain, thermal storage, solar grow and change, providing inexpensive, greenhouses, roof ponds, and convection sustainable alternatives for common loops, all have their own advantages and heating and cooling systems. As technology disadvantages as well. The main drawback improves and awareness increases, passive to implementing these strategies into a solar energy will become more widely used building is a need for further planning and throughout the country and around the specific materials. However, this increased world. It is certainly a viable option for new initial cost only increases the long-term construction, and will continue to assist in savings for a building using passive solar saving energy for many. energy. The use of these approaches to

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