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Green libraries are a part of the larger green building movement. Also known as sustainable libraries, green libraries are being built all over the world, with many high profile projects bringing the concept into the mainstream. Along with library 2.0, green design is an emerging trend, defining the library of the 21st century. Many view the library as having a unique role in the green building movement due to its altruistic mission, public and pedagogical nature, and the fact that new libraries are usually high profile, community driven projects.
What makes a library green? 
There are many ways to define a green library, but there are a number of central themes that run through all of them, including, minimizing the negative impact the building will have on the local environment, and if possible having a positive impact. Reducing the use of water and energy by designing in a way that maximizes the use of natural and renewable resources. Integrating actual greenery and vegetation into the building and site design; Preferably, using drought resistant and/or native vegetation. And, maintaining high standards of indoor air quality to help ensure the health of the people who inhabit the building.
Despite the fact that there are many paths to sustainable design, the emergence of the trend has created a demand for quantifiability. In the United States, the non-profit organization the United States Green Building Council (USGBC) developed the Leadership in Energy and Environmental Design (LEED) rating system in the year 2000. Their point based rating has a total of 100 base points possible, and buildings can be categorized as certified (40 points), silver (50), gold (60), or platinum (80+). LEED uses five different categories to judge a building's sustainability; 1) site location, 2) water conservation, 3)energy efficiency, 4) materials, 5) indoor air quality, and a bonus category for innovation and design. As of 2003 libraries accounted for 16% of all LEED projects (Brown, 2003).
Special needs 
Sustainable library design is strongly tied to the overall green building movement, but libraries have specific needs that present some extra challenges for green builders.
The biggest challenge is balancing the sometimes conflicting needs of the patrons and the materials. One of the central themes of the library's mission is to preserve knowledge, so that it can be passed on to future generations. For over a thousand years books have been the dominant way to do that. While the internet has become the information medium of choice for many, books still play a very important role in the preservation of knowledge. In order to be preserved, books must be kept away from extreme temperatures, moisture, and sunlight. In contrast, many individuals find sunlight to be the most enjoyable light for reading. Sunlight also plays a major role in green design, because it can be used to reduce the reliance on artificial lighting. For a long time, libraries needed to protect the collection from the damaging ultra-violet rays of the sun. New developments in glass technology over the past ten years have given designers more flexibility in their ability to place collections (Mcabe, 2003).
Another, often overlooked, challenge the library presents is the weight of the books. A common strategy in green design is to raise the floors to increase circulation, but the weight of the stacks can be an impediment to this strategy. To deal with this challenge, many designers have resorted to zoning the library into designated areas, so these strategies can be enacted in certain areas, and alternatives can be used in others. Libraries need to be built flexibly, in order to make room for expansions in size and in wiring capabilities. Library buildings are long term investments into the community, so when designing them architects need to be looking 50 or 100 years into the future. These obstacles by no means present insurmountable challenges to green libraries. The special needs of the library just need to be taken into consideration from the beginning of the project.
How are libraries becoming green? 
Green design is an integrated process. No one aspect of a building's architecture makes it green architecture. Without proper integration from the earliest moments of the planning phase, redundancies can occur, eliminating many of the potential benefits of sustainable design. Good sustainable design capitalizes on the synergistic relationships that occur between the various design elements. LEED groups these elements into five categories. Buildings can be designed in a way in which, good design in one category helps another category fulfill its goal.
Site selection 
Before building can start, a site must be chosen. The selection of the site has a large impact on how ecologically friendly the library will be. LEED has a number of guidelines to help the site selection process. There are a number of questions to consider that will help guide the site selection process, including, what kind of impact will construction have on the local environment, will there be erosion, what can be done with storm runoff, and is the site already green? Also, the library should be located in a densely populated area, near a number of other service related buildings. People should be able to reach the building via public transportation and the parking lots should give priority parking to those driving energy efficient automobiles. The heat island effect can be reduced by shading hard surfaces, putting them underground, or by implementing a vegetative roof (LEED, 2005)
Water conservation 
There are many different ways for libraries to conserve water. A number of them rely on proper site selection. If a site is selected properly strategies can be used to capture rainwater runoff to be used in irrigation. Another strategy is to use low flow fixtures, and waterless urinals.
Energy conservation 
Energy efficiency is considered by many to be the most important category in becoming sustainable. In the LEED rating system it is the heaviest weighted of all the categories. Energy efficient design is in many ways a return to passive design principles that evolved over thousands of years, until the advent of air conditioning and cheap energy made those strategies appear to be unnecessary. After air conditioning became widely available, buildings were designed to eliminate influences of the outside environment. Lamis illustrates this point in "Greening the Library" when he compares two libraries built near the turn of the 20th century, the New York Public Library and the Boston Public Library; to two more recently built libraries, the Chicago Public Library and the Phoenix Public Library. The two older libraries have interior spaces that are narrow, so they can be reached by natural light and air. Whereas the two more modern libraries have large floor plans, with interior spaces far removed from the outside environment. Making them more dependent on artificial systems of temperature control.
As environmental awareness increases, as well as the cost of fossil fuels needed to operate giant heating, air conditioning, and ventilation ([HVAC]) systems, building designers are beginning to recognize that the outside environment cannot be ignored, and should be taken advantage of. What 21st-century designers are beginning to do is implement ancient passive design principles, while taking advantage of the most advanced technology available.
The passive strategies vary according to location, but they are always implemented to capitalize on the natural elements, mostly wind and sun, to manage the temperature and to provide ventilation and light. Active strategies are more technologically advanced solutions that include using various forms of renewable energy resources and using sensors to adjust lighting. Using photovoltaic cells that turn sunlight into energy is becoming an increasingly popular way to reduce energy dependence. In order to fully maximize energy efficiency and comfort, libraries are combining passive and active strategies.
Building materials 
It is believed that up to 40% of landfill space is filled with construction waste material. The primary responsibility in selecting materials for the library is to contribute as little waste as possible. Another responsibility is to choose materials that can be produced without causing too much damage to the natural environment. In order to fulfill the first responsibility, post-industrial and post-consumer recycled materials are being used. When purchasing materials claiming to be made from recycled goods it is important to investigate what their claims mean. It is a common marketing practice to exaggerate how green a product is by using misleading statements. Also, materials should be chosen that are going to be able to be reused or recycled 50–100 years down the road when the library building has reached the end of its useful life (Tseng, 2007). As non-renewable resources decrease, reusing and recycling are going to become increasingly necessary in the future.
It is also important to consider where materials are coming from: Resources have emerged to help guide the material selection process, such as the Forest Stewardship Council (FSC). They rate and certify wood based on a number of factors regarding how it was produced; rights of indigenous peoples, environmental impact, workers rights, efficiency, management, and conservation (FSC, 1996). Another material option is using quickly renewable materials such as bamboo in place of wood whenever possible. The widening availability of green building materials, along with the development of non-profit watchdog groups are two important factors in the greening of 21st-century library buildings.
Indoor air quality 
Along with energy inefficiency, poor air quality has been another side-effect of the post air conditioning building design. Because most modern buildings are temperature controlled, they are designed to be airtight. The lack of ventilation can not only make buildings expensive to cool, it also traps harmful toxins that can do serious damage to people's respiratory systems. Toxins come from a variety of sources. Materials that make up the library, including paints and carpeting, have volatile organic compounds (VOC's), which produce a ground-level ozone after reacting with sunlight and nitrogen. The carbon dioxide that people breathe into the atmosphere is another toxin. To improve air quality, materials can be bought that have a low VOC content, and CO2 monitors can be installed to ensure that CO2 levels remain at a safe level. On average, people spend about 90% of their time indoors. Therefore, green buildings need to be designed in a way in which the air gets recycled, and does not stay stagnant. A green library is not just about taking care of the environment, it is about taking care of the health and well-being of those who work in it and patronize it.
Why are libraries becoming green? 
First, libraries have been expanding the scope of their mission statements, to include working for the betterment of mankind. Second, technology is no longer a barrier. Third, it is great for the image of the library. Finally, sustainability offers the library a degree of independence, because cost of maintenance goes down, as does reliance on the volatile fossil fuels market.
All libraries have a mission statement, and spoken or unspoken, libraries are here to improve the condition of mankind. An institution can no longer, in good faith aim to improve the human condition while contributing to the destruction of the future: Buildings produce about 40% of the dangerous greenhouse gasses emitted into the atmosphere (Anisko & Willoughby, 2006). The environmental debate has evolved. The fact that humans are having a negative impact on the environment is no longer seriously questioned. Now, two questions shape the debate: What is our responsibility to fix it, and what can we do to fix it? Individuals and private organizations have a right to find their personal answers to those questions, but libraries are an investment in the future of our society. Libraries have a responsibility to not contribute to the destruction of the environment, to educate the people regarding our current situation, and empower them to make a difference. Libraries are discovering that their green building gives them a great opportunity to educate the citizenry (Tseng, 2007). As libraries continue to take a more progressive stance on improving the human condition, sustainability will have to be a central theme.
The availability of the technology and knowledge to build green buildings has passed a tipping point. Green buildings are constructed all over the world in every sector of the economy; residential, commercial, non-profit, government, etc. Another breakthrough is the diversity of green technology. There is an abundance of options, so any green builder has the ability to capitalize on the local natural resources available, and customize the building to most efficiently operate in the local environment. Along with the advancement of technology, the increasing awareness of environmental issues decrease the burden on the green builder. With the development of organizations like the USGBC and the FSC, green builders have information resources available to them. These organizations offer measurable levels of achievement to strive for, along with acting as watchdogs to help prevent the exaggeration of green credentials or "green-washing." With these advances, sustainable construction is no longer a utopian fantasy, but is simply becoming the way good buildings are being built.
The library is undergoing an identity transformation. It is struggling to stay relevant, as a vocal minority predicts its demise. While its image as an outdated institution is not entirely deserved, it is trying to assert itself as an irreplaceable part of the community, that plans on being an assertive force for good in the 21st century. Green design helps it do that three different ways. 1) A sustainable building makes a statement that the library is investing in the future of the community. 2) Sustainable buildings are smartly designed, aesthetically pleasing, and are powered by state-of-the-art technology. When people see these emerald marvels they will no longer be able to maintain false stereotypes regarding libraries as anachronistic relics from an analog age. 3) More and more people take environmentalism seriously, so a green image is a good image. The public awareness on this issue is only going to increase. Libraries want the public to believe that they are still relevant, and that their mission is to better humankind. Many have decided that a green library is a physical manifestation of their mission statement, and it provides an image of how libraries want to be seen in the 21st century.
As publicly funded institutions, libraries are constantly battling with budget issues. Swings in the economy can affect the tax dollars coming into the library, as well as new legislation. Sustainable design offers libraries a way to reduce maintenance and energy costs, providing them with a degree of independence. Thanks to computer modeling software, building planning can be done more efficiently than in the past. Precise estimations on quantity of building materials can prevent waste and save money. Simulations can also be done to predict how big of an HVAC system the library needs. Solar 5.5 is a computer program that builds a 3-D model of the library's energy performance, and then plugs in various passive and active design strategies to see what kind of effect they would have on each other to maximize the energy savings and cost of the building; it has saved some California libraries up to 46% of the energy cost compared to meeting minimum state requirements (Boyden & Weiner, 2000).
One of the most important features of green design is a shift from the reliance on depleting fossil fuels to renewable energy resources. The independence from fossil fuels will save the library large sums of money, and it will relish its independence if prices continue to rise.
Money will also be saved by having higher morale, health, and productivity from employees. The architectural firm Heschong Mahone conducted a study that indicated students perform 25% better on standardized tests when in classrooms lit naturally. High levels of CO2 can decreases performance as well. Savings can also be increased, because there are governmental incentives to capitalize on, and some utility companies offer incentives too (Boyden & Weiner, 2001).
Because of the long-term nature of the library, green design is potentially less expensive than standard design, as heavy up-front costs often pay for themselves, waste is reduced, efficiency is increased, and energy and water are conserved. Evolving libraries of the 21st century are integrating sustainable practices, because it is becoming the most cost-effective way to do things.
High-profile green libraries 
In the 2000s (decade) a number of high-profile green libraries have been built in the U.S. and in the rest of the world.
Fayetteville (AR) Public Library 
The Fayetteville Public Library designed by Meyer, Scherer and Rockcastle, Ltd. in Minneapolis opened in October 2004. The library, Library Journal's 2005 Library of the Year, was the first building in Arkansas to register with the U.S. Green Building Council and achieved the silver LEED designation in 2006. To earn this designation the library employed many green-design techniques. The library was built on an empty lot a few blocks away from the city's bustling square, making it a textbook infill project. During construction, any trees removed were harvested and used for furniture or donated to local parks. Throughout the project, almost 99% of the construction waste was recycled or reused. More than 65% of the materials used to build the library were made within 500 miles (800 km) of the city. By incorporating a green roof and using alternative roofing materials, the design team reduced air temperature as much as 20 degrees. Water collected on the roof is reused for landscape irrigation. The library's green roof saves about $4,000 a year in energy savings. The building's reading spaces and circulation desks were situated to take advantage of the natural sunlight without over-working the building's air conditioners, reducing energy costs by 25% and the overall building's energy consumption by 30%. Sunlight streams through 75% of the building's public spaces.
Seattle Central Library 
The Seattle Central Library designed by Rem Koolhaas opened in May 2004. It employs a number of innovative techniques to achieve the status of a green library. It is located in a dense urban area, accessible by public transportation. Rainwater runoff is stored in a 40,000 gallon tank, and used to irrigate the landscape. It has triple glazed glass, used to reduce heat buildup. Seventy-five percent of the demolition and construction waste was recycled. Many other green strategies were employed that can be read in more detail here: SPL's green strategies
National Library, Singapore 
The Singapore National Library has been called the greenest building on the planet. Designed by Ken Yeang, it opened in July 2005. It is designed using light shelves that allow the light to filter into the library, without having any harsh effects. During the moments that the sun is either to bright or not bright enough, sensors are programmed to dim or brighten the lights, and raise and lower the shades to maximize comfort and reduce costs (Anisko & Willoughby, 2006)
Minneapolis Public Library 
The Central Branch of the Minneapolis Public Library System was designed by Cesar Pelli, and it opened in May 2006. It has a 18,560-square-foot (1,724 m2) green roof. The green roof is planted with vegetation that does well in Minnesota's harsh climate, and it reduces rainwater runoff, reduces the building's heating and cooling load, reduces the buildings heat island effect, and adds green space to the downtown cityscape (MPL, 2006).
Public Library of Charlotte and Mecklenburg County 
The Joe and Joan Martin Center is the first public building in Charlotte and Mecklenburg County certified by the US Green Building Council. In 2006, ImaginOn was awarded LEED certification at the silver level.
Children's Museum of Pittsburgh 
The Children's Museum of Pittsburgh underwent extensive expansion and renovation in 2004 using sustainable techniques and guiding principles thereby earning silver LEED-certification, one of largest museums in the country to receive this designation, and the first children’s museum in America to do so. For more detailed information, see The Green Museum
University of California, Merced Kolligian Library 
Opened in August 2005, UC Merced's Kolligian Library was awarded Gold Leeds Certification in 2007. The 180,000-square-foot (17,000 m2) glass-and-concrete building uses 42% less water and 50% less energy than comparable buildings. The building's carpet contains 37% recycled content, while its acoustical ceiling tiles contain 66% recycled content that includes telephone books and newspapers. Nearly 30% of the materials used to construct the building were manufactured locally, resulting in significant transportation and energy savings.
The list of green libraries is growing all the time. For an up to date information on green libraries and green library projects in the U.S. and Canada see green libraries.
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