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Review and Assessment of the Health and Productivity Benefits of Green Schools: An Interim Report Executive Summary BACKGROUND At the request of the Massachusetts Technology Collaborative (MASSTECH), the Barr and Kendall Foundations, the Connecticut Clean Energy Fund, and the U.S. Green Building Council, 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, has held four meetings. A fifth meeting will be held in January 2006, and the committee will complete its final report by April 30, 2006. This interim report has been prepared at the request of MASSTECH. MASSTECH is preparing a legislative proposal for green school guidelines, to be submitted to the Massachusetts School Building Authority in December 2005. MASSTECH has requested a summary of the committee’s findings and recommendations to date as guidance in finalizing its proposal. Because this is an interim report, it is important to note that the committee has not yet fully addressed the statement of task. The committee has developed an evaluation framework (task 2) and has reviewed and assessed some of the empirical and theoretical studies that address some characteristics of green schools and their associations with the health and development of students and teachers (task 1). In this interim report, the committee has dealt with five characteristics of green schools—building envelope, ventilation, lighting, acoustics, and condition—and evaluated the scientific evidence for relationships/associations with various outcomes of health, learning, and productivity (task 3). The committee plans to review and assess
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Review and Assessment of the Health and Productivity Benefits of Green Schools: An Interim Report additional characteristics of green schools and the evidence for associations with health and development and report the results of those assessments in its final report. To fulfill the statement of task, the committee will also synthesize the results of all of the assessments (overall task) and identify avenues of research that represent 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 (task 4). COMPLEXITY OF THE TASK The charge to this committee is to review and assess existing empirical and theoretical studies on the possible connections between characteristics of green schools and the health and performance of students and teachers. Such an evaluation would ideally be based on a generally accepted definition of green schools that would convey specific architectural features, systems, and operational practices. However, there is no single, accepted definition among educational professionals, architects, and others, of what constitutes a “green school.” Instead, there are many definitions with varying levels of detail for green schools (sometimes referred to as “high-performance green schools” or “high-performance schools”). The definitions typically focus on environmental or other objectives to be achieved through “green” or sustainable design processes, features, and practices. Various sets of guidelines have been developed to suggest a multitude of ways in which the objectives can be achieved to some degree. Typically the guidelines move well beyond design and engineering criteria for school buildings to address land use, processes for construction and equipment installation, and operation and maintenance practices. The committee’s task is further complicated by the fact that green schools are not standardized in their design and there are relatively few schools considered as exemplifying green design. Adding to the complexity is the need to draw on literature from a wide array of professional disciplines, including medicine, education, architecture, and engineering. These disciplines have developed differing research methodologies and criteria for determining causality. The committee also recognizes that many factors in a school as well as in a community and individual households influence the educational achievement of individuals and schools systems. Those factors or variables can be difficult to control for or measure in evidence-based studies, which, in turn, limits the inferences that can be drawn. In addition, the effects of the built environment will necessarily appear to be small, given the number of variables. COMMITTEE’S APPROACH Given these complexities, the committee’s approach was to identify those characteristics of green schools that are typically emphasized in the current definitions and guidelines and that differ from conventional new school construction norms. The committee also identified those characteristics that potentially have a level of importance for health and learning outcomes. In this interim report, the committee focuses on the following
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Review and Assessment of the Health and Productivity Benefits of Green Schools: An Interim Report characteristics of green school buildings and their relationships to occupant health and productivity outcomes: Building envelope, moisture management, and health; Ventilation, pollutant source control, health, and productivity; Lighting, performance, and health; Acoustics, student learning, and teacher health; and Building condition and student achievement. In evaluating the scientific literature related to these topics, the committee has relied on a hierarchy of evidence for scientific inference developed by the National Academies (Box ES.1) for use in health-related studies (IOM, 1991, 1993, 1994, 1996, 1999, 2003). This hierarchy has played an important role in the committee’s deliberations. Box ES.1 National Academies’ Hierarchy of Evidence for Scientific Inference in Health-Related Studies Sufficient Evidence of a Causal Relationship: Evidence is sufficient to conclude that a causal relationship exists between the agent and the outcome. That is, the evidence fulfills the criteria for sufficient proof of an association, and in addition, satisfies evaluation criteria such as strength of association, biologic gradient, consistency of association, biologic plausibility and coherence, and temporally correct association. The finding of sufficient evidence of a causal relationship between an exposure and a health outcome does not mean that the exposure would inevitably lead to that outcome. Rather it means that the exposure can cause the outcome, at least in some people under some circumstances. Sufficient Evidence of an Association: Evidence is sufficient to conclude that there is an association. That is, an association between the agent and the outcome has been observed in studies in which chance, bias, and confounding can be ruled out with reasonable confidence. Limited or Suggestive Evidence of an Association: Evidence is suggestive of an association between the agent and the outcome but is limited because chance, bias, and confounding could not be ruled out with confidence. For example, at least one high-quality study shows a positive association, but the results of other studies are inconsistent. Inadequate or Insufficient Evidence to Determine Whether or Not an Association Exists: The available studies are of insufficient quality, consistency, or statistical power to permit a conclusion about the presence or absence of an association. Alternatively, no studies exist that examine the relationship. Limited or Suggestive Evidence of No Association: Several adequate studies are consistent in not showing an association between the agent and the outcome. A conclusion of “no association” is inevitably limited to the conditions, magnitude of exposure, and length of observation covered by the available studies. SOURCE: IOM, 2004.
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Review and Assessment of the Health and Productivity Benefits of Green Schools: An Interim Report FINDINGS AND RECOMMENDATIONS Finding 1: In its review thus far, the committee has found the following: There are no well-designed, evidence-based studies concerning the overall effects of green schools on the health or development of students and teachers, in part because the concept of green schools is quite new. There are, however, a few well-designed studies that examine specific building features often emphasized in green school design and the effects of these components on health and learning. Given the level of interaction between people and their environments and other confounding factors, establishing cause-and-effect relationships between an attribute of a school building and its effect on students, teachers, and staff is difficult. The effects of the built environment will necessarily appear to be small, given the number of variables. Empirical measures do not, however, necessarily capture all relevant considerations that should be applied when evaluating research results. Qualitative aspects of the environment are also important. Thus, in the committee’s collective judgment, there is value in attempting to identify design features and building processes and practices that may lead to improvements in learning, health, and productivity for students, teachers, and other school staff, even if empirical results are less than robust. Finding 2: In regard to issues related to building envelope, moisture management, and health, the committee has found the following: There is sufficient evidence to establish an association between moisture problems in buildings (floods, visible dampness, leaks, mold growth in spaces or in heating, ventilation, and air-conditioning [HVAC] systems) and adverse health outcomes, particularly asthma and respiratory symptoms, among children and adults. Excessive moisture in a building can lead to structural damage, deterioration of the performance of building systems and components, and cosmetic damage, all of which can result in increased maintenance and repair costs. Guidelines for green schools typically do not adequately address the design detailing, construction, and long-term maintenance of building envelopes to ensure that allergen sources are controlled, moisture is controlled, and a building is kept dry over the long term. Well-designed, constructed, and maintained building envelopes are critical to the control and prevention of the excessive moisture and molds that have been associated with adverse health effects in children and adults. Designing for effective moisture management will likely have benefits for the building, including lower life-cycle costs. Excellent resources for proper moisture control design include The Moisture Control Handbook, Principles and Practices for Residential and Small Commercial Buildings by Joseph Lstiburek and John
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Review and Assessment of the Health and Productivity Benefits of Green Schools: An Interim Report Carmody (1994) and The Building Foundation Design Handbook (ORNL, 1988), published by Oak Ridge National Laboratory. Recommendation 1: The control of excessive moisture, dampness, and molds to protect the health of children and adults in schools and to protect the structural integrity of a building should be a key objective for green schools. MASSTECH should develop guidelines that specifically address moisture control as it relates to the design, construction, operation, and maintenance of a school building’s envelope (foundations, walls, windows, and roofs); ventilation systems; and related items such as siting, landscaping, and plumbing systems. Finding 3: In regard to ventilation, pollutant source control, health, and performance, the committee has found the following: Numerous pollution sources and building system characteristics affect air quality in a school. The most important determinants of indoor air quality are (1) design and operation of the ventilation system to limit the buildup of pollutants and humidity and achieve thermal comfort, (2) control of indoor sources of pollutants, and (3) control of outdoor sources of pollutants. There is a robust body of evidence indicating that the health of children and adults can be affected by air quality in a school. A growing body of evidence suggests that teacher productivity and student learning, as measured by absenteeism, may be affected by indoor air quality as well. Indoor pollutants and allergens from house dust mites, pet dander, cockroaches, and rodents also contribute to increased respiratory and asthma symptoms among children and adults. The reduction of pollutant loads, both sensory and not, has been shown to reduce the occurrence of building-associated symptoms and to improve the health and comfort of people occupying the buildings. Although compliance with the American Society for Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) standards for ventilation rates may be the minimal acceptable standard for green schools, there is good evidence that increasing the ventilation rate beyond the ASHRAE standard will further improve comfort and productivity. However, an upper limit on the ventilation rates, indicating when the benefits of outside air begin to decline, has not been established. The committee will address additional issues related to heating, ventilation, air-conditioning, and their associations with health and productivity outcomes in its final report. Until this review is completed and the results are synthesized, the committee will defer making specific recommendations. Finding 4: In regard to lighting, performance, and health, the committee has found the following:
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Review and Assessment of the Health and Productivity Benefits of Green Schools: An Interim Report Daylight is a special light source because it may provide a view (through a window), high light levels, and good color rendering, and it is ever-changing. Direct and reflected sunlight can create significant visual problems if windows, skylights, and clerestories allow in too much or too little light. However, such problems can be controlled with manual blinds and other types of window treatments. There is good evidence from studies of adult populations that the visual conditions in schools resulting from both electric lighting and daylighting are adequate for most children and adults. There is, however, concern that a significant percentage of students in classrooms do not have properly corrected eyesight, and thus, the general lighting conditions suitable for visual functioning by the average student may be inadequate for those students without properly corrected eyesight. It could be hypothesized that daylight may benefit these children by providing higher light levels and better geometries than would otherwise be present from electric lighting alone. However, the potential advantages of daylight in classrooms for improving visual performance of children with or without properly corrected eyesight has not been systematically studied. Because of inconsistent results and the small number of well-designed studies, there is insufficient evidence at this time to determine whether or not an association exists between daylighting and student performance. A growing body of evidence suggests that lighting may play an important nonvisual role in human health and well-being through the circadian system. However, the effect of light on health through circadian regulation of sleep, depression, and cell cycle has not been directly studied in children. Recommendation 2: To determine the potential and actual performance of a lighting system, the entire system should be assessed because total performance cannot be effectively evaluated based solely on the source of illumination or on the individual components needed to create the entire lighting system. Recommendation 3: For green schools in which the lighting strategy is to use daylight extensively, control systems that can be easily operated, such as manual blinds or other types of window treatments, should be specified in order to control excessive sunlight or glare. Finding 5: In regard to noise, acoustics, student learning, and teacher health, the committee has found the following: Sufficient evidence exists to conclude that there is an association between decreased noise levels in schools and improvement in student achievement. Although there is strong evidence that reduced noise levels are most important for younger children because they are still developing speech discrimination, additional research is required to more precisely define possible needs for control of reverberant sound for younger children.
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Review and Assessment of the Health and Productivity Benefits of Green Schools: An Interim Report Some available evidence indicates that teacher health, in regard to voice impairment, may be adversely affected by noisier environments, although the magnitude of the effect cannot currently be estimated as a function of exposure to noise. Recommendation 4: To facilitate student learning, guidelines for green schools should include requirements to meet American National Standards Institute (ANSI) Standard S12.60, “Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools.” Finding 6: In regard to building condition and student achievement, the committee has found the following: The body of available research is suggestive of an association between the condition of a school building and student achievement. All of the studies analyzed by the committee found that student test scores improved as the physical condition of school buildings improved. The degree of improvement of students’ test scores varied across the studies, but in all cases students in buildings in better condition scored higher than students in buildings in poor condition. Recommendation 5: Guidelines for green schools should place significant emphasis on operations and maintenance practices if potential health and productivity benefits are to be achieved and maintained over the lifetime of a building.
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