1
Introduction

Americans have long cherished the belief that a well-educated citizenry is necessary to the national well-being. School buildings are the places where children come together to learn basic civics as well as the skills they need to become productive members of society: Schools are the locus of education. Local schools have been the center of efforts to provide equal educational opportunities to all segments of the population. School buildings also host other activities, including adult education classes, voting, and community events. In some cases, a school may symbolize the community itself and may have intrinsic value for social coherence.

The concept that the design of school buildings may affect students’ and teachers’ health and development is not new. A report on the State of Maine’s Schools in 1886 linked moisture, lighting, and ventilation of school buildings to health and learning:

Nearly one sixth of the population of our State spends about six hours daily during a large part of the year in our school rooms. This necessary confinement within the school room walls, coming as it does during the growing period of the body, and while it is most susceptible to harmful influences, entails certain evils which have been too generally regarded as necessary accompaniments of school life. It is generally well known, however…. that most of the diseases incident to school life are in quite a high degree preventable…. [O]ne of the first and most important requirements in guarding against these diseases is to have the building of school-houses conform to a few rules….



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Green Schools: Attributes for Health and Learning 1 Introduction Americans have long cherished the belief that a well-educated citizenry is necessary to the national well-being. School buildings are the places where children come together to learn basic civics as well as the skills they need to become productive members of society: Schools are the locus of education. Local schools have been the center of efforts to provide equal educational opportunities to all segments of the population. School buildings also host other activities, including adult education classes, voting, and community events. In some cases, a school may symbolize the community itself and may have intrinsic value for social coherence. The concept that the design of school buildings may affect students’ and teachers’ health and development is not new. A report on the State of Maine’s Schools in 1886 linked moisture, lighting, and ventilation of school buildings to health and learning: Nearly one sixth of the population of our State spends about six hours daily during a large part of the year in our school rooms. This necessary confinement within the school room walls, coming as it does during the growing period of the body, and while it is most susceptible to harmful influences, entails certain evils which have been too generally regarded as necessary accompaniments of school life. It is generally well known, however…. that most of the diseases incident to school life are in quite a high degree preventable…. [O]ne of the first and most important requirements in guarding against these diseases is to have the building of school-houses conform to a few rules….

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Green Schools: Attributes for Health and Learning School-houses should be built on dry ground; if not dry, the lots must be deeply drained…. The reason for this rule is the well-known fact that dampness of soil contributes much to make a school-house unhealthy…. The light which comes from considerably above the level of the desks and books lights them much better than the more horizontal rays. High windows also light the ceiling, whence the light is reflected downward upon the desks…. Never think that a school-room is completed until there is some way of getting fresh, warmed air into it and the foul, breathed air out. Ventilation costs something in fuel, but it is a penny-wise and pound-foolish policy which omits it (State of Maine, 1887). More than a hundred years later, scientific research has demonstrated that building design, materials, systems, operation, maintenance, and cleaning practices can affect occupants’ health and development. Buildings also affect the natural environment, in the resources used and the pollutants emitted. As shown in Table 1.1, buildings account for more than 40 percent of U.S. energy use as well as a significant amount of raw materials, water, and land. Buildings also produce 40 percent of atmospheric emissions, including greenhouse gases, and significant amounts of solid waste and wastewater. Recognizing these adverse environmental impacts, a movement to design and operate buildings using methods and technologies that conserve energy and other natural resources—often called green building, high-performance building, or sustainable design—emerged in the 1990s and continues to grow. This movement emphasizes designing, constructing, operating, and maintaining buildings to reduce their adverse environmental impacts through the use of recycled materials, energy-efficient equipment, and other features and practices. The potential environmental benefits of green school buildings are significant: A 2002 survey of 851 public schools districts found that an average of $176 per pupil was spent for energy. This figure is likely to be higher in 2006 owing to across-the-board increases in the price of gas, oil, and electricity. If energy and other TABLE 1.1 Environmental Burdens of Buildings, U.S. Data Resource Use Share of Total (%) Pollution Emissions Share of Total (%) Raw materials 30 Atmospheric emissions 40 Energy use 42 Water effluents 20 Water use 25 Solid waste 25 Land (SMSAsa) 12 Other releases 13 aStandard Metropolitan Statistical Areas. SOURCE: Data from Levin (1997).

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Green Schools: Attributes for Health and Learning building-related costs can be reduced, the money saved could be used for other educational purposes. Because research on the effects of the indoor environment on people and research on the effects of buildings on the environment are converging, there is value in determining whether some building designs, technologies, and practices that help to support human health and development can also benefit the natural environment. This study, then, is intended to look beyond the environmental objectives established for “green” schools and to assess the research-based evidence related to their effects on student learning, teacher productivity, and the health of students, teachers, and staff. The results of this study should be of interest to a wide range of stakeholders, including school administrators, school district business managers, federal and state education officials, parents, teachers, and architects and engineers specializing in school design, both green and conventional. SCHOOL CONSTRUCTION AND RELATED ISSUES More than 62 million Americans spend a significant portion of their time in school buildings. The National Center for Education Statistics (NCES) reports that in 2002 more than 123,000 elementary and secondary schools, with a combined enrollment of 54 million students, were operating in the United States (Table 1.2) (NCES, 2002). Approximately 7.3 million people were employed to provide teaching and education-related services in public schools: 3 million teachers; 2.9 million education-related staff; and 1.4 million support services staff. Complete data for private schools were not available. On average, public schools invested $7,900 per pupil per year to provide educational services, which equates to $39.5 million per year for a public school district with 5,000 students. TABLE 1.2 Statistics for Elementary and Secondary Schools in the United States, 2002   Total Public Private Schools 123,382 94,112 29,270 Students enrolled (in millions) 54.6 48.2 6.4 Teachers employed (FTEs) 3,425,400 3 million 425,400 Education-related staff   2.9 million Not available Support services staffa   1.4 million Not available Average expenditure per studentb   $7,900   aIncludes school and district administrators, librarians, guidance counselors, instructional aides, and supervisors. bIncludes persons providing food, health, library assistance, maintenance, transportation, security, and other services. SOURCE: NCES (2002).

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Green Schools: Attributes for Health and Learning The NCES projects that by 2014, total enrollments will increase by approximately 2 million, to 56.7 million, and the number of teachers employed will increase by 500,000, to 3.9 million. Expenditures per public school student are forecasted to increase to $10,000 by 2014, or $50 million for a district with 5,000 public school students. The primary responsibility for providing an educational system rests with each of the 50 states and the District of Columbia. The majority of funding for educational programs is provided by state and local authorities, although the federal government does provide some funding tied to policy initiatives such as the No Child Left Behind Act (P.L. 107-110). School building construction and renovation also require a substantial commitment of resources—dollars, time, materials, expertise. Capital costs alone typically will total tens of millions of dollars. The decision to invest this level of funding most often rests with the local school governing body and usually requires a bond referendum voted upon by the residents of the school district. The process of authorizing funding for construction may take several years (Figure 1.1). Once funds are allocated, it may take 2 to 5 more years for a school building to be designed, constructed, and occupied. A school building’s size and design (which affect initial capital costs and long-range operating costs) are a function of the current and projected school population, local resources, the curriculum, and other community uses. For example, the educational literature abounds with articles touting the virtues of small neighborhood schools (Cotton, 2001; Raywid, 1996). Advocates for smaller schools argue that such schools are better at improving the academic achievement of students who have not been successful in traditional settings, leading to higher graduation rates, and other benefits. Others argue that the cost of moving to smaller schools is too great. To date, the scientific evidence is mixed as to whether smaller or larger schools produce better academic results. The ongoing debate about the purpose and nature of public education also has implications for school building design, and costs. If public education becomes increasingly focused on producing good scores on standardized achievement tests, for instance, curriculums may increasingly focus on traditional academic subjects, and the demand for music, art, vocational, and physical education courses may diminish. School buildings designed to support this type of curriculum might be composed primarily of standard academic classrooms with few spaces for so-called “nonessential” subjects. In contrast, a curriculum based on the premise that learning is holistic—with, for example, art incorporated into language arts or math taught with specific job skills or vocations in mind—may require school buildings in which standard academic class-

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Green Schools: Attributes for Health and Learning FIGURE 1.1 Typical process for funding school buildings. rooms largely disappear, to be replaced by specialized labs and learning centers (Lackney, 1999). Another possibility is schools that are created or redesigned so that instructional and support spaces can also be used by social and community organizations or even businesses. Schools in which teaching might be individualized through Web-based teaching are also being discussed. Classrooms in such schools would contain computers but few other materials, such as books. Thus, public discussion and decision making about the size of schools—large or small—and educational curriculums, have significant implications for the design of schools, construction materials and resources, their long-term operation and maintenance costs, and the tax dollars that will be invested in them. Implicit in these discussions is the assumption that school design does have a role in supporting educational goals and outcomes. Once built, a school typically is used for educational purposes for 30 years or longer. During that time, changes in functional requirements or new programmatic ideas may drive the reconfiguration of classrooms or the upgrading of libraries, science laboratories, or other specialized space. While the building is in service, the investment made in its operation, maintenance, and repair will be six to eight times greater than the initial

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Green Schools: Attributes for Health and Learning cost of construction.1 For that reason, a focus on the lifetime costs of a building, not just the first costs of design and construction, is important for effective decision making and the long-term economic health of a community. A SCHOOL BUILDING AS A SYSTEM OF SYSTEMS A school, like other buildings, is a system of systems. A school building’s overall performance is a function of the indoor and outdoor environments, the activities taking place within it and on its grounds, the occupants, how intensely it is used (9 or 12 months of the year, by how many people), the initial design, and long-term operation and maintenance practices. Indoor environmental quality—the level of air pollutants, temperature, humidity, noise, light, space—is a function of the interrelationship of a building’s foundations, floors, walls, roofs, heating, ventilation, and air conditioning (HVAC) systems, electrical and plumbing systems, telecommunications, materials, and furnishings. HVAC systems, for example, affect a range of indoor environmental factors, including pollutant levels, temperature, humidity, noise, air quality, moisture control, and sensory loads (odors). The location of air intakes, the efficiency of ventilation filters, and operation practices all will affect the amount and quality of outdoor air used to ventilate indoor spaces. The optimum size and capacity of an HVAC system is dependent on the orientation of the building, the total square footage, the quality of insulation, the number of windows, and other factors. The orientation of a school to maximize solar gain might help reduce heating costs during the winter but increase cooling costs in the summer. If the HVAC system design does not adequately factor in these variables, the system may be too large and energy inefficient. Numerous other examples of the interrelationships between the design and operation of a building system and the indoor environmental quality could be cited. In all cases, indoor environmental quality can and will deteriorate over time if buildings are not properly designed, systems are not operated appropriately, or needed maintenance and repairs are deferred. Although the interactions and interdependencies of building systems and their various components are known by building designers, individual systems and elements are typically treated as separate components, 1 The annual operation and maintenance costs of a building, however, will be only a fraction of the annual costs to operate a school, which includes the salaries and benefits of teachers, administrators, and support staff; educational equipment and supplies; food service; and other expenses.

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Green Schools: Attributes for Health and Learning with attention devoted to the specification and performance of each individual structural subsystem. This sequential approach to design and construction reflects the organization of the design and construction industry into individual trades and specialties. Research on the effects of the built environment on people also tends to focus on specific building features or practices as opposed to overall design or building performance. Because building systems and components are designed and installed as independent entities, some systems may be optimized at the expense of others, and potential conflicts among design objectives may not be recognized. For example, providing for good acoustical quality in classrooms may require that ventilation and air-conditioning ducts be lined with sound-absorbing materials. However, if some materials used for this purpose are not properly installed and maintained, microbial contamination can occur and negatively affect the indoor air quality. A “systems” philosophy of design considers these types of interactions and recognizes that compromises or trade-offs among elements may be necessary to optimize overall building performance. When school building design and performance are being considered, the element of time cannot be overemphasized. School building materials and components wear out at differing rates, vary in their complexity, the ways in which they are operated, and the costs of maintaining them. So, although a building’s foundations and walls may last for 50 to 100 years, the roof will probably wear out after 20 years and the air-conditioning system in 15 years. The durability of materials, the level of maintenance undertaken, the timeliness and quality of the maintenance, the climate, and other factors will affect the service lives and performance of various systems and components. SCHOOL BUILDING PERFORMANCE Although most school buildings perform well when first built, their performance can and will deteriorate if the systems are not operated appropriately, if preventive maintenance programs are ineffective, or if needed maintenance and repairs are deferred. Because overall building performance is difficult to measure directly, overall building condition is often used as a surrogate. Professional organizations and governmental agencies have been reporting on the condition of the nation’s schools (AASA, 1983; Council of Great City Schools, 1987; Educational Writers’ Association, 1989; GAO, 1995a, 1995b; NEA, 2000) for 25 years. These reports consistently found that a substantial portion of the school-age population was being educated in substandard buildings. And schools with higher concentrations of students from low-income households were more likely to be in substandard condition.

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Green Schools: Attributes for Health and Learning In School Facilities: Condition of America’s Schools, the U.S. General Accounting Office estimated that approximately 14 million students (30 percent of all students) attended schools that needed extensive repairs or replacement (one-third of the school inventory) as of 1995 (GAO, 1995a). Approximately 28 million students attended schools that needed extensive repairs on one or more major building systems. The building components or features most often identified as needing attention in substandard schools were thermal control (temperature and humidity), ventilation, plumbing, roofs, exterior walls, finishes, windows, doors, electrical power, electrical lighting, life safety (fire suppression), and interior finishes and trims. The cost to make necessary repairs was estimated at more than $100 billion (1995 dollars). A second GAO report, School Facilities: America’s Schools Not Designed or Equipped for 21st Century, found that approximately 40 percent of the schools surveyed could not meet the functional requirements for teaching laboratory science or large groups (GAO, 1995b). About two-thirds of the schools could not support educational reform measures such as private space for counseling and testing, parental support activities, social/health care, day care, and before- and after-school care. In 2000, the NCES reported that at least 29 percent of the nation’s public elementary and secondary schools had problems with heating, ventilation, and air conditioning; 25 percent had plumbing problems; 24 percent reported problems with exterior walls, finishes, windows, and doors; and about 20 percent had less than adequate life safety, roofs, and electrical power. About 11 million students attended school in districts reporting less-than-adequate buildings, of whom approximately 3.5 million were in schools whose condition was rated as poor, which needed to be replaced, or in which significant substandard performance was apparent (NCES, 2000). The NCES also found that: Schools in rural areas and small towns were more likely than schools in urban fringe areas and large towns to report that at least one of their environmental conditions was unsatisfactory (47 percent compared with 37 percent), Schools with the highest concentrations of households with incomes below the poverty level were more likely to report at least one unsatisfactory environmental condition than were schools with lower concentrations of low-income households (55 percent compared with 38 percent), and About one-third of school administrators were dissatisfied with the energy efficiency of their schools, and 38 percent were dissatisfied with the flexibility of instructional space.

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Green Schools: Attributes for Health and Learning “GREEN” BUILDING MOVEMENT Although the history of environmentally responsive design is centuries old, the term “green building” (also called “sustainable designx building” or “high-performance building”) is relatively new. The goal is to design buildings that meet performance objectives for land use, transportation, energy efficiency, indoor environmental quality, and other factors. Statements describing green objectives vary. The Office of the Federal Environmental Executive, for example, defines green building as “the practice of (1) increasing the efficiency with which buildings and their sites use energy, water, and materials, and (2) reducing building impacts on human health and the environment, through better siting, design, construction, operation, maintenance, and removal—the complete building life cycle” (OFEE, 2003). An Urban Land Institute publication (Porter, 2000, p. 12) defines “sustainable” as designing projects and buildings in ways that Conserve energy and natural resources and protect air and water quality by minimizing the consumption of land, the use of other nonrenewable resources, and the production of waste, toxic emissions, and pollution; Make cost-effective use of existing and renewable resources such as infrastructure systems, underused sites, and historic neighborhoods and structures; Contribute to community identity, livability, social interaction, and sense of place; Widen access to jobs, affordable housing, transportation choices, and recreational facilities; and Expand diversity, synergism, and use of renewable resources in the operation and output of the local economy. To enable building owners and design teams to evaluate the energy and environmental performance of their buildings, a voluntary system for rating green buildings has been developed for new construction by an expert-intensive process of the U.S. Green Building Council (USGBC). The USGBC’s Leadership in Energy and Environmental Design (LEED) rating system awards credits for designing to advance sustainable site development, water savings, energy efficiency, indoor environmental quality, and materials selection. Buildings are rated as “certified,” “silver,” “gold,” or “platinum,” depending on the total number of credits received. To receive LEED certification a building must first comply with the most up-to-date national standards. Credits can also be earned for innovative designs. The first version of LEED was issued in 1998 and has since been revised several times (the most recent version is LEED 2.2). The revisions

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Green Schools: Attributes for Health and Learning have involved hundreds of environmental professionals and industries engaged in defining energy and environmental sustainability for a range of building types, for commercial interiors (LEED-CI), for existing buildings (LEED-EB), for commercial construction and major renovation projects (LEED-NC), and for neighborhood development (LEED-ND). GREEN SCHOOL GUIDELINES A consortium of state and utility leaders in California launched an effort in 2001 to develop energy and environmental standards specifically for schools. The Collaborative for High Performance Schools (CHPS, often pronounced “chips”) aims to increase the energy efficiency of California schools by marketing information, services, and incentive programs directly to school districts and designers. The CHPS Web site defines green schools as having the following 13 attributes: “healthy, comfortable, energy efficient, material efficient, water efficient, easy to maintain and operate, commissioned, environmentally responsive site, a building that teaches, safe and secure, community resource, stimulating architecture, and adaptable to changing needs” (CHPS, 2005). Green school objectives are to be achieved through guidelines that are similar to the LEED rating system but specifically geared to schools. Similar guidelines have been issued by Washington state (WSBE, 2005) and are in development in Massachusetts and other states.2 Green school guidelines move well beyond design and engineering criteria for the buildings themselves, addressing land use, processes for construction and equipment installation, and operation and maintenance practices. They include design and engineering techniques to meet specific objectives: Locating schools near public transportation to reduce pollution and land development impacts; Placing a building on a site so as to minimize its environmental impact and make the most of available natural light and solar gain; Designing irrigation systems and indoor plumbing systems to conserve water; Designing energy and lighting systems to conserve fossil fuels and maximize the use of renewable resources; Selecting materials that are nontoxic, biodegradable, and easily recycled and that minimize the impacts on landfills and otherwise reduce waste; and 2 LEED for Schools is under development in 2006, in collaboration with CHPS.

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Green Schools: Attributes for Health and Learning Creating an indoor environment that provides occupants with a comfortable temperature, and good air quality, lighting, and acoustics. Green school guidelines also recommend construction techniques to meet objectives such as the appropriate storage of materials on construction sites to avoid water damage, the reduction of waste materials and appropriate disposal to reduce resource depletion, and the introduction of commissioning practices3 to ensure the performance of building systems. Operation and maintenance practices to achieve good indoor environmental quality include using nontoxic cleaning products, replacing air filters in ventilation systems regularly, and establishing a long-term indoor environmental management plan. Because they follow conventional design and construction practice, current green school guidelines typically treat materials, lighting, ventilation systems, windows, and other building components as individual elements, not as interrelated systems. They allow designers to accumulate credits by optimizing certain components or systems (e.g., energy efficiency) while suboptimizing or ignoring others (health and development). In doing so, such guidelines fail to account for the interrelationships among systems, occupants, and ongoing practices. Nor do they identify the potential need for compromises or trade-offs among design objectives in order to optimize overall building performance as it relates to multiple objectives. In 2005, the Massachusetts Technology Collaborative (MASSTECH) promulgated draft guidelines for green school construction and major renovations in Massachusetts based on both the California CHPS and the most recent LEED® standards. MASSTECH defined a high-performance green school as having three distinct attributes: It is less costly to operate than a conventional school; It is designed to enhance the learning and working environment; and It conserves important resources such as energy and water. 3 Commissioning is “a quality-focused process for enhancing the delivery of a project. The process focuses on verifying and documenting that the facility and all of its systems and assemblies are planned, designed, installed, tested, operated to meet the Owner’s Project Requirements” (ANSI, 2004, p. 1). Commissioning is discussed in detail in Chapter 9.

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Green Schools: Attributes for Health and Learning STATEMENT OF TASK At the request of MASSTECH, the Barr Foundation, the Kendall Foundation, the Connecticut Clean Energy Fund, and the USGBC, the National Research Council (NRC), through the Board on Infrastructure and the Constructed Environment (BICE), appointed the Committee to Review and Assess the Health and Productivity Benefits of Green Schools. The committee’s charge was to “review, assess, and synthesize the results of available studies on green schools and determine the theoretical and methodological basis for the effects of green schools on student learning and teacher productivity.” In the course of the study, the committee was asked to do the following: Review and assess existing empirical and theoretical studies regarding the possible connections between the characteristics of “green schools” and the health and productivity of students and teachers. Develop an evaluation framework for assessing the relevance and validity of individual reports that considers the possible influence of such factors as error, bias, confounding, or chance on the reported results and that integrates the overall evidence within and between diverse types of studies. Report the results of this effort in a manner that will facilitate the identification of causal relationships and the subsequent implementation of beneficial practices. Identify avenues of research that represent potentially valuable opportunities to leverage existing knowledge into a better understanding of the relationships between green building technologies in schools and the performance of students and teachers. The committee, appointed in January 2005, was composed of experts in education, green building technology, student performance, sustainable design, indoor environments, buildings and health, epidemiology, materials, infectious diseases, school design, management, and administration, and research methodology. The committee held five 2- or 3-day meetings between April 2005 and January 2006 and was briefed by the study sponsors, by experts in building design and operation, and by researchers. The committee also toured the Capuano green school in Somerville, Massachusetts, and held several conference calls. An interim report was published in January 2006 (http://fermat.nap.edu/catalog/11574.html). FINDING AND RECOMMENDATIONS Finding 1: School buildings are composed of many interrelated systems. A school building’s overall performance is a function of interactions

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Green Schools: Attributes for Health and Learning among these systems, of interactions with building occupants, and of operations and maintenance practices. However, school buildings are typically designed by specifying individual components or subsystems, an approach that may not recognize such interactions. Current green school guidelines reflect this approach and, in so doing, they allow for buildings focused on specific objectives (e.g., energy efficiency) at the expense of overall building performance. Recommendation 1a: Future green school guidelines should place greater emphasis on building systems, their interrelationships, and overall performance. Where possible, future guidelines should identify potential interactions between building systems, occupants, and operation and maintenance practices and identify conflicts that will necessitate trade-offs among building features to meet differing objectives. Recommendation 1b: Future green school guidelines should place greater emphasis on operations and maintenance practices over the lifetime of a building. Systems that are durable, robust, and easily installed, operated, and maintained should be encouraged. ORGANIZATION OF THE REPORT Although the committee has already emphasized the need for a systems approach to buildings, the report is generally organized by various building features. This construct is necessary because research on the built environment, like building design, typically focuses on specific features and systems, as opposed to overall performance. Following the discussion in Chapter 2, “Complexity of the Task and the Committee’s Approach,” Chapters 3 through 7 discuss specific elements of indoor environmental quality and their effects on human health, learning, and productivity. Each chapter begins by identifying issues, then discusses design requirements and solutions related to those issues, and ends with a discussion of current green school guidelines. These discussions are generalized and primarily based on the committee’s review of the CHPS, Washington State, and draft MASSTECH guidelines and supporting documents. Chapter 3, “Building Envelope, Moisture Management, and Health,” focuses on excess moisture or dampness in buildings, its effects on human health, and the building envelope as a source of excess moisture. Chapter 4, “Indoor Air Quality, Health, and Performance,” discusses indoor air quality as a function of pollutant loads, temperature, humidity, and ventilation rates, and how these factors are related to human health and development.

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Green Schools: Attributes for Health and Learning Chapter 5, “Lighting and Human Performance,” focuses on lighting quality as it affects both the visual and circadian systems, the relationship of light to learning and development, and sources of light and their various qualities. Chapter 6, “Acoustical Quality, Student Learning, and Teacher Health,” describes how noise levels affect speech intelligibility and student learning, and how excessive noise may relate to voice impairment among teachers. Chapter 7, “Building Characteristics and the Spread of Infectious Diseases,” addresses the issue of common infectious diseases (colds and flu and other viral infections) and building interventions that can help to interrupt the transmission of these diseases. Chapter 8, “Overall Building Condition and Student Achievement,” summarizes the findings of a number of published and unpublished studies looking at overall conditions and functionality of school buildings and their effects on student achievement. Chapter 9, “Processes and Practices for Planning and Maintaining Green Schools,” highlights the importance of participatory planning, setting up commissioning processes, monitoring building performance, postoccupancy evaluations, and training for educators and support staff. Chapter 10, “Linking Green Schools to Health and Productivity: Research Considerations,” summarizes the committee’s specific suggestions for future research on green schools and discusses factors to be considered in designing such research. Because indoor environmental quality is a composite of air quality, light and noise levels, temperature, humidity, and other factors and a result of the interactions of various building systems, some topics are discussed in more than one chapter. Thus, excess moisture in buildings and its relation to health is discussed in Chapters 3 (building envelope), 4 (indoor air quality) and 7 (building characteristics and the spread of infectious diseases). NOTE TO READERS Research literature from a diverse set of disciplines and from U.S. and international studies is reviewed and cited in this report. Two systems of measurement, English and metric, were used in the original studies. For example, some research on ventilation rates uses liters per person per second as a measure, while other research uses cubic feet per minute or air exchanges per hour. The committee provides explanations of the measures as appropriate. However, it has not attempted to convert such measures to a common standard, because doing so could result in inadvertent errors that would detract from this report and its findings.