School buildings are special places. They are the locus of education, the places where children come together to learn about civics and develop basic skills to be productive members of society. Schools are also used for adult education classes, voting, community events, and other activities, and may symbolize the community itself.
Research has shown that the quality of indoor environments can affect the health and development of children and adults. Buildings, including schools, also affect the natural environment, accounting for 40 percent of U.S. energy use and 40 percent of atmospheric emissions, including greenhouse gases. In the 1990s, the “green building” movement emerged to promote methods for designing buildings that have fewer adverse environmental impacts. Various guidelines have been developed to implement green building objectives.
SCOPE OF THE STUDY
At the request of the Massachusetts Technology Collaborative (MASSTECH), the Barr Foundation and the Kendall Foundation, the Connecticut Clean Energy Fund, and the U.S. Green Building Council, the National Research Council (NRC) 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.” The committee was also asked to look at the possible
connections between green schools and student and teacher health. 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, and teachers, as well as architects and engineers specializing in school design, both green and conventional.
COMPLEXITY OF THE TASK AND THE COMMITTEE’S APPROACH
The line of reasoning inherent in this study’s task—mapping connections from physical environments to student and teacher outcomes (health, learning, productivity)—poses significant challenges. Numerous factors contribute to the complexity of the task, including the lack of a clear definition of what constitutes a green school, the variations in current green school guidelines, the difficulty of measuring educational and productivity outcomes, the variability and quality of the scientific literature, and confounding factors. All of these factors are described in Chapter 2.
Lacking specific guidance, the committee identified those building characteristics and practices typically emphasized in current green school guidelines. The committee determined that green schools have two complementary, but not identical, goals and resulting outcomes. The goals are (1) to support the health and development (physical, social, intellectual) of students, teachers, and staff by providing a healthy, safe, comfortable, and functional physical environment; and (2) to have positive environmental and community attributes. Because they were first developed to minimize adverse environmental effects, current green school guidelines place less emphasis on features supporting human health and development. In line with its charge, the committee focused on outcomes associated with student and teacher health, learning, and productivity.
The committee developed a conceptual model for evaluating the links between green school buildings and outcomes (Figure ES.1).
The conceptual model assumes that a green school building’s location and design (site; orientation; envelope; heating, ventilation, and air conditioning; acoustics; lighting) will result in an indoor environment with appropriate (or inappropriate) levels of moisture, ventilation, air quality, noise, lighting, and other qualities. It also assumes that the indoor environment will be modified by season (e.g., presence of airborne pollen), over time (e.g., mold growth from chronic water leakage), and by operational, maintenance, repair, and cleaning practices. Finally, the indoor environment can affect student learning and health and teacher health and productivity.
GREEN SCHOOL BUILDING ATTRIBUTES THAT WOULD SUPPORT HEALTH AND DEVELOPMENT
After evaluating the research literature, the committee concluded that a green school with the following attributes would support student and teacher health, learning, and productivity:
Dryness: Excessive moisture, which has been associated with adverse health effects, particularly asthma and respiratory diseases, is not present.
Good indoor air quality and thermal comfort: Ventilation rates, air pollutants, humidity levels, and temperature ranges, which have been linked to human health, learning, and productivity, are effectively controlled.
Quietness: The acoustical quality, which has been shown to affect student learning and the development of language skills, meets the newly released Standard 12.60, “Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools,” of the American National Standards Institute.
Well-maintained systems: Building systems are commissioned1 to ensure that they perform as intended, and their performance is monitored over time. Routine preventive maintenance is implemented throughout a school’s service life.
Cleanliness: Surfaces are disinfected to interrupt the transmission of infectious diseases, and measures are implemented to help control indoor pollutants that have been associated with asthma and other respiratory diseases.
Additional green school attributes that should be aspired to include durability, increased acoustical quality for more sensitive groups, and improved cleaning practices to prevent the accumulation of allergens and irritants. The committee’s specific findings and recommendations are presented below.
FINDINGS AND RECOMMENDATIONS
Finding 1: School buildings are composed of many interrelated systems. A school building’s overall performance is a function of interactions 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.
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.
Complexity of the Task
Finding 2a: Given the complexity of interactions between people and their environments, establishing cause-and-effect relationships between an attribute of a green school or other building and its effect on people is very difficult. The effects of the built environment may appear to be small given the large number of variables and confounding factors involved.
Finding 2b: The committee did not identify any well-designed, evidence-based studies concerning the overall effects of green schools on human health, learning, or productivity or any evidence-based studies that analyze whether green schools are actually different from conventional schools in regard to these outcomes. This is understandable because the concept of green schools is relatively new, and evidence-based studies require a significant commitment of resources.
Finding 2c: Scientific research related to the effects of green schools on children and adults will be difficult to conduct until the physical characteristics that differentiate green from conventional schools are clearly specified. With outcomes as complex as student and teacher health, student learning, and teacher productivity influenced by many individual family and community factors, it may be possible in theory to design research that controls for all potentially confounding factors, but difficult in practice to conduct such research.
Recommendation 2: The attributes of a green school that may potentially affect student and teacher health, student learning, and teacher productivity differently than those in conventional schools should be clearly specified. Once specified, it may be possible to design appropriate research studies to determine whether and how these attributes affect human health, learning, and productivity.
Building Envelope, Moisture Management, and Health
Finding 3a: There is sufficient scientific evidence to establish an association between excess moisture, dampness, and mold in buildings and adverse health outcomes, particularly asthma and respiratory symptoms, among children and adults.
Finding 3b: Excess moisture in buildings can lead to structural damage, degraded performance of building systems and components, and cosmetic damage, all of which may result in increased maintenance and repair costs.
Finding 3c: Well-designed, -constructed, and -maintained building envelopes are critical to the control and prevention of excess moisture and molds. Designing for effective moisture management may also have benefits for the building, such as lower life-cycle costs.
Finding 3d: Current green school guidelines typically do not adequately address the design detailing, construction, and long-term maintenance of buildings to ensure that excess moisture is controlled and a building is kept dry during its service life.
Recommendation 3a: Future green school guidelines should emphasize the control of excess moisture, dampness, and mold to protect the health of children and adults in schools and to protect a building’s structural integrity. Such guidelines should 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) and related items such as siting and landscaping.
Recommendation 3b: Research should be conducted on the moisture resistance and durability of materials used in school construction. Such research should also investigate other properties of these materials such as the generation of bioaerosols and indoor pollutants as well as the environmental impacts of producing and disposing of these materials.
Indoor Air Quality, Health, and Performance
Finding 4a: A robust body of scientific evidence indicates that the health of children and adults can be affected by indoor air quality. A growing body of evidence suggests that teacher productivity and student learning may also be affected by indoor air quality.
Finding 4b: Key factors in providing good indoor air quality are the ventilation rate; ventilation effectiveness; filter efficiency; the control of temperature, humidity, and excess moisture; and operations, maintenance, and cleaning practices.
Finding 4c: Indoor air pollutants and allergens from mold, pet dander, cockroaches, and rodents also contribute to increased respiratory and asthma symptoms among children and adults. Although limited data are available regarding exposure to these allergens in U.S. schools, studies in both school and nonschool environments support the notion that allergen levels can be decreased through good cleaning practices.
Finding 4d: The reduction of pollutant loads through increased ventilation and effective filtration has been shown to reduce the occurrence of building-associated symptoms (eye, nose, and throat irritations; headaches; fatigue; difficulty breathing; itching; and dry, irritated skin) and to improve the health and comfort of building occupants.
Finding 4e: There is evidence that ventilation rates in many schools do not meet current standards of the American Society for Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE). Available research indicates that increasing the ventilation rate to exceed the current ASHRAE standard will further improve comfort and productivity.
Finding 4f: Scientific evidence indicates that increased ventilation rates can reduce the incidence of building-related symptoms, reduce pollutant loads associated with asthma and other respiratory diseases, and improve the productivity of adult workers. Increased ventilation rates may also reduce the potential for reactions among airborne pollutants that generate irritating products and may improve perceived air quality. However, the research conducted to date has not established an upper limit on the ventilation rates, above which the benefits of outside air begin to decline.
Finding 4g: Research comparing the effects of natural versus mechanical ventilation on human health is inconclusive. However, there is evidence that improper design, maintenance, and operation of mechanical ventilation systems contribute to adverse health effects, including building-related symptoms among occupants.
Finding 4h: Studies in office buildings indicate that productivity declines if room temperatures are too high. However, there are few studies investigating the relationship of room temperatures to student learning, teacher productivity, and occupant comfort.
Finding 4i: To date, no systematic research has examined the relationship of cleaning effectiveness to student and teacher health, student learning, or teacher productivity. Few studies have looked systematically at changes in exposures, health, or productivity based on changes in building materials, cleaning products, or cleaning practices.
Recommendation 4a: Future green school guidelines should ensure that, as a minimum, ventilation rates in schools meet current ASHRAE standards overall and as they relate to specific spaces. Future guidelines should also give consideration to planning for ventilation systems that
can be easily adapted to meet evolving standards for ventilation rates, temperature, and humidity control.
Recommendation 4b: Future green school guidelines should emphasize the importance of appropriate operation and preventive maintenance practices for ventilation systems, including replacing filters, cleaning coils and drip pans to prevent them from becoming a source of air pollution, microbial contamination, and mold growth. These systems should be designed to allow easy access for maintenance and repair. The Environmental Protection Agency’s Tools for Schools program is a well-recognized source of information on methods for achieving good indoor air quality.
Recommendation 4c: Additional research should be conducted to document the full range of costs and benefits of ventilation rates that exceed the current ASHRAE standard and to determine optimum temperature ranges for supporting student learning, teacher productivity, and occupant comfort in school buildings.
Recommendation 4d: Studies should be conducted to examine the relationships of exposures from building materials, cleaning products, and cleaning effectiveness to student and teacher health, student learning, and teacher productivity.
Lighting and Human Performance
Finding 5a: The research findings from studies of adult populations seem to indicate clearly that the visual conditions in schools resulting from both electric lighting and natural light (daylighting) should be adequate for most children and adults, although this supposition cannot be supported by direct evidence.
Finding 5b: There is concern that a significant percentage of students in classrooms do not have properly corrected eyesight, and so the general lighting conditions suitable for visual functioning by the most students may be inadequate for those students who need but do not have corrective lenses. It could be hypothesized that daylight might benefit these children by providing higher light levels and better light distribution (side light) than would electric lighting alone. However, the potential advantages of daylight in classrooms for improving the visual performance of children without properly corrected eyesight has not been systematically studied.
Finding 5c: Current green school guidelines typically focus on energy-efficient lighting technologies and components and the use of daylight to
further conserve energy when addressing lighting requirements. Guidance for lighting design that supports the visual performance of children and adults, based on task, school room configurations, layout, and surface finishes, is not provided.
Finding 5d: Windows and clerestories can supplement electric light sources, providing high light levels, and good color rendering. Light from these sources is ever-changing and can cause glare unless appropriately managed. Currently, there is insufficient scientific evidence to determine whether or not an association exists between daylight and student achievement.
Finding 5e: 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, little is known about the effects of lighting in schools on student achievement or health through the circadian system.
Recommendation 5a: Future green school guidelines should seek to support the visual performance of students, teachers, and other adults by encouraging the design of lighting systems based on task, school room configurations, layout, and surface finishes. Lighting system performance should be evaluated in its entirety, not solely on the source of illumination or on individual components.
Recommendation 5b: Future green school guidelines for the design and application of electric lighting systems should conform to the latest published engineering practices, such as the consensus lighting recommendations of the Illuminating Engineering Society of North America.
Recommendation 5c: Green school guidelines that encourage the extensive use of daylight should address electric control systems and specify easily operated manual blinds or other types of window treatments to control excessive sunlight or glare.
Recommendation 5d: Because light is important in regulating daily biological cycles, both acute effects on learning and lifelong effects on children’s health should be researched, particularly the role that lighting in school environments plays in regulating sleep and wakefulness in children.
Acoustical Quality, Student Learning, and Teacher Health
Finding 6a: Most learning activities in school classrooms involve speaking and listening as the primary communication modes. The intelligibility of
speech in classrooms is related to the levels of speech sounds relative to the levels of ambient noise and to the amount of reverberation in a room.
Finding 6b: Sufficient scientific evidence exists to conclude that there is an inverse association between excessive noise levels in schools and student learning.
Finding 6c: The impacts of excessive noise vary according to the age of students, because the ability to focus on speech sounds is a developmental skill that does not mature until about the ages of 13 to 15 years. Thus, younger children require quieter and less reverberant conditions than do adults to hear equally well. As adults, teachers may not appreciate the additional problems that excessive noise creates for younger students.
Finding 6d: Excessive noise is typically a more significant problem than is too much reverberation in a classroom. It is not possible to have both increased speech level (to maximize signal to noise) and reduced reverberation times. Good acoustical design must be a compromise that strives to increase speech levels without introducing excessive reverberation.
Finding 6e: The most substantial body of research related to excessive noise and learning in the classroom addresses the impacts of road traffic, trains, and airport noise.
Finding 6f: Some available evidence indicates that teachers may be subject to voice impairment as a result of prolonged talking in noisy school environments. However, there is no information to quantify a relationship between specific noise levels in classrooms and potential voice impairment.
Recommendation 6a: To facilitate student learning, future green school guidelines should require that new schools be located away from areas of higher outdoor noise such as that from aircraft, trains, and road traffic.
Recommendation 6b: Future green school guidelines should specify acceptable acoustical conditions for classrooms and should require the appropriate design of HVAC systems, the design of walls and doors separating classrooms and corridors, and the acoustic quality of windows and walls adjoining the outdoors. This recommendation is most easily achieved by requiring that green schools comply with American National Standards Institute (ANSI) Standard 12.60, “Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools.”
Recommendation 6c: Additional research should be conducted to define optimum classroom reverberation times more precisely for children of various ages.
Building Characteristics and the Spread of Infectious Disease
Finding 7a: Common viruses and infectious diseases can be transmitted by multiple routes: through the air, by person-to-person contact, and by touching contaminated surfaces (fomites). Certain characteristics of buildings, including the cleanliness of surfaces, relative humidity, and ventilation effectiveness, influence the transmission of common viruses. Evidence from studies in nonschool environments suggests that interventions which interrupt the known modes of transmission of common infectious agents may decrease the occurrence of such illnesses in schoolchildren and staff.
Finding 7b: The best way to control infections, especially gastroenteritis, appears to be instituting procedures that promote good hand cleansing. Available but limited information indicates that hand sanitizers are superior to the routine washing of hands.
Finding 7c: Cleaning of surfaces that are commonly touched (e.g., doors, faucets, desktops) is effective for interrupting the transmission of infectious agents. Disinfecting surfaces with water and detergents is apparently as effective as applying germicidal agents.
Finding 7d: The use of no-touch faucets, doorways, receptacles, and equipment seems to be a reasonable, though unproven, method for infection control.
Finding 7e: The survival, dispersal, and removal of airborne pathogens are affected by relative humidity, ventilation rate, and the percentage of recirculated air in the air supply. Increased ventilation rates have been shown to speed the dilution and removal of viral material. The use of displacement ventilation and the reduction of the percentage of recirculated air in the air supply have the potential to reduce building occupants’ exposures to airborne pathogens.
Finding 7f: Ultraviolet germicidal irradiation (UVGI) may be effective for inactivating and killing some infectious organisms, but its use in school room applications has not been systematically studied.
Recommendation 7a: Future green school guidelines should include measures for the regular cleaning of commonly touched surfaces and the availability of hand sanitizers at sinks. The use of “no-touch” faucets, receptacles, equipment, and egress from bathrooms should be considered, taking into account the age of the children in the school.
Recommendation 7b: Full-scale classroom and school studies should be conducted to quantify the efficacy of a variety of ventilation strategies, including displacement ventilation and the elimination of recirculated air, for the dispersion and removal of airborne infectious agents. Studies should also quantify the potential costs and benefits of such ventilation strategies.
Recommendation 7c: Additional research should be conducted to determine the optimal infection-control interventions in terms of measurable outcomes such as absenteeism and academic achievement. One line of research is the use of ultraviolet germicidal irradiation in supplemental or portable air-cleaning devices in school room applications and its effects on human health.
Overall Building Condition and Student Achievement
Finding 8: The methodologies used in studies correlating overall building condition with student achievement are not adequate to determine if there is a relationship between overall building condition and student test scores. This research tradition seems to address a more general and diffuse question and does not produce high-quality evidence relative to either school design or specific aspects of maintenance. Improved research for understanding how specific building conditions affect student and teacher performance would measure one or more building performance characteristics, develop a theory linking those characteristics and student and/or teacher outcomes, and test the linkage using adequate measures of the outcomes of interest and fully specified regression models.
Processes and Practices for Planning and Maintaining Green Schools
Finding 9a: Participatory planning, commissioning, and postoccupancy evaluation are processes that can both lower building operating costs and improve performance over a building’s lifetime. Current green school guidelines typically only address the practice of building commissioning.
Finding 9b: Inadequate planning for schools carries long-term fiscal, human, and academic costs. A strong planning process requires asking
the right questions, involving a full range of stakeholders, and having a clear sense of purpose.
Finding 9c: A commissioning process that starts in the planning phase and continues through building occupancy can help ensure that a school building performs in accordance with the stated design criteria and the owner’s operational requirements. Effective commissioning for green schools requires specific expertise in nontraditional elements such as moisture control, indoor air quality, lighting, and acoustics.
Finding 9d: If a green school’s performance and potential benefits are to be maintained over its service life, building systems and features should be monitored. Such monitoring can include the use of sensors and other technologies that provide data about current indoor environmental conditions and the likely performance of a building over time.
Finding 9e: Postoccupancy evaluations can help ensure the performance of existing schools and help improve the design of future schools.
Finding 9f: Green schools represent a significant public investment. That investment can be undermined if educators, support staff, students, and other stakeholders do not have the knowledge or training to appropriately use or operate a green school.
Recommendation 9a: Future green school guidelines should stress the importance of good planning processes that allow for the effective participation of a wide range of stakeholders.
Recommendation 9b: Future green school guidelines should require for all new schools a building commissioning process that begins in planning and continues through occupancy. The commissioning agent should specifically verify that moisture-management features are properly designed and installed, that intended ventilation rates are delivered to building occupants, that the lighting system is adequately designed and installed to ensure effective lighting based on tasks and school room configurations, and that acoustical measures meet the performance standards of ANSI Standard 12.60.
Recommendation 9c: Future green school guidelines should encourage the periodic monitoring of indoor environmental characteristics including moisture levels, absolute humidity, classroom temperatures, and ventilation effectiveness to ensure that performance objectives are maintained over the service life of a school.
Recommendation 9d: Educators, support staff, students, and other stakeholders should be informed of the design intent of a green school and given the appropriate information or training to fulfill their roles in using and operating a green school.
Linking Green Schools to Health and Productivity: Research Considerations
Finding 10a: Much is still not known about the potential interactions of building systems, materials, operation and maintenance practices and their effects on building occupants in general, or about school environments in particular. The necessary collaboration between architecture, engineering, physical science, medicine, and social science expertise is a challenge, but multidisciplinary research is required to fully study the potential relationship between a school building and the outcomes of students and teachers.
Finding 10b: In designing research studies to evaluate the unbiased effects of green schools on student learning or student and teacher health, several issues must be addressed. These include defining green schools for the purpose of scientific inquiry, defining performance and productivity outcomes plausibly related to green schools, and fully developing a theory explaining the links between green school design and health and learning effects. Finally, the hypotheses from these theories should be tested in ways that reduce systematic biases and provide compelling evidence about these linkages.
Finding 10c: Currently, the theory and evidence connecting green schools or characteristics associated with green schools to teacher or student outcomes is not sufficient to justify large-scale evaluations. However, the committee does consider it useful to carry out studies that assess the positive and negative consequences of the design and construction features as well as building performance characteristics that are associated with green schools using more rigorous study designs.
Finding 10d: Large-scale evaluations using randomized experiments and econometric or regression-based techniques should be conducted if they are justified from the results of smaller and less expensive studies, such as those outlined in Finding 10c. Finally, it is possible that improvements to the large-scale data sets that contain student achievement data will allow for relatively low cost studies of the effects of the school building environment on student achievement, which the committee considers to be an important side benefit.