The environmental impacts of human activity have been a source of controversy and concern for many years. Much of the focus over that time has been on impacts such as pollution and the destruction or degradation of wildlife habitats and ecosystems. Over the past few decades, however, concerns have increased greatly about greenhouse gases, resource depletion, and degradation of ecological services such as water supply. Over that time, the impacts of buildings have come under increasing scrutiny. There are many different kinds of buildings—residential, commercial, government, and those with special uses such as schools and hospitals—and they form a large and core component of the nation's infrastructure. The construction, characteristics, operation, and demolition of buildings are now recognized as a major source of environmental impact, including direct effects on the humans who use them. U.S. buildings consume vast amounts of resources annually in the form of electricity for lighting and temperature control, drinkable water for indoor and outdoor use, and construction materials with diverse supply chains and manufacturing processes; they also produce substantial waste streams throughout their lifecycles, from construction to daily operations to demolition. Such resource use can impose high environmental and financial costs. For example, buildings account for about 40% of energy consumption in the United States, producing approximately 40% of anthropogenic greenhouse gas emissions, and costing consumers more than $430 billion a year in energy bills. A building's location and interaction with its surrounding environment also influences its ecological and human health impacts. Buildings create impermeable surfaces that can have substantial effects on stormwater management and associated health and environmental impacts. A building's proximity to public transportation affects the energy required to transport occupants to and from the premises. If an office is not accessible by walking or public transit, for example, occupants may need to commute by car, contributing to traffic delays, smog, and greenhouse gas emissions. Occupant health and productivity is also affected by building features that determine indoor air quality. Most people spend far more time indoors than outside, and the air in buildings often has substantially higher concentrations of pollutants than the air outside, contributing in extreme cases to a phenomenon known as "sick building syndrome." These and other undesirable environmental and health impacts can be addressed for construction, renovation, and operations of both new and existing buildings. Green building is a tool for transforming the ways in which buildings are designed, built, operated, and demolished that has generated substantial interest in recent decades. Since emerging as a relatively novel concept in the 1990s, green building has grown into what many consider a respected approach to building, with an increasing number of stakeholders. They include, among others, private construction firms, building owners and occupants, green building certification and standards-developing organizations, federal and state lawmakers, local code officials, and a variety of government agencies. This report discusses the concept of green building, major federal policies and programs relating to it, and associated issues. Topics covered include how green building is defined, what it consists of, the major areas of environmental impact it seeks to address, an overview of the tools available for ensuring that a building conforms to green criteria, outstanding issues in the implementation of green building, an overview of the major statutory and executive authorities that address it, and programs in federal agencies that involve one or more elements related to it. Environmentally sensitive building is not a particularly recent phenomenon, but the modern practice of green building began emerging in the 1990s. One milestone in the United States was the formation in 1990 of the Committee on the Environment within the American Institute of Architects (AIA), followed within a few years by the founding of the U.S. Green Building Council (USGBC) and other organizations. The most prominent federal green building project in that decade was the "Greening of the White House." From those beginnings, the concept of green building has expanded to encompass both the movement to promote environmentally conscious design principles and the set of practices and strategies by which builders seek to reduce harmful impacts of the built environment. There is no single consensus definition of green building; efforts exist along a design and performance continuum. What some call green building is barely distinguishable from standard building practices. At the extreme, the term can be used in an almost meaningless way, purely as a marketing tool. Such practices are sometimes called "greenwashing." In contrast, some practitioners aim to provide buildings with environmental impacts that are greatly reduced from those of typical buildings. Examples include the so-called "zero-impact" building, which is intended to have no net environmental impact, including but not limited to net-zero energy use; and the "minus-impact" building, which would provide a net environmental benefit (see " Net-Zero Buildings ," below). Most green building efforts have less ambitious reduction goals. In general, green building might best be characterized as an integrated approach to building design, construction, and operations that significantly reduces the environmental footprint of buildings in comparison to standard practices. The environmental footprint is the overall impact of a structure or activity on the environment, including the human environment. This characterization captures two common features of the various meanings given to the term. First, green is a relative concept—a green building is one that is greener than average. Second, it is not limited to only one factor, such as energy consumption, but involves integration across several, as is discussed below. The green building approach can be applied to any class of building: large or small, commercial or residential. Green builders seek to achieve improvements in environmental performance through a variety of techniques and strategies, from the implementation of innovative technologies (such as energy-efficient heating and cooling systems) to design features intended to influence occupant behavior (such as placing stairways prominently to encourage their use). Some of these techniques will be discussed in more detail below. Decisions about which of these techniques will be used are often made in the design and planning phase, but can impact the environmental footprint of a building throughout its lifecycle. As a result, green building techniques are most often applied to new construction, through there is a growing incidence of green renovation and retrofit projects. The term green building is often used interchangeably with others such as sustainable building , and that practice is followed in this report. However, the terms may also be used in ways that are not exactly synonymous. For example, sustainable building may be described as a form of green building, but with a more stringent goal of indefinitely maintaining environmental footprints that are small enough that they will not impede future human activity and the functioning of ecosystems. Another term often used interchangeably with green building is high-performance building. However, high-performance building usually involves other factors such as security in addition to environmental ones. There are two federal statutory definitions: a building that integrates and optimizes all major high-performance building attributes, including energy efficiency, durability, life-cycle performance, and occupant productivity, and a building that integrates and optimizes on a life cycle basis all major high performance attributes, including energy conservation, environment, safety, security, durability, accessibility, cost-benefit, productivity, sustainability, functionality, and operational considerations. Additional objectives may also be considered in the design of high-performance buildings, including aesthetics and historical preservation. The " Energy Independence and Security Act of 2007 " (EISA) further refined the concept by establishing a detailed definition for high-performance green buildings (see " Definitions of Green Building ," above). Descriptions of green building generally focus on specified elements, which in various documents may also be referred to by other terms such as attributes, life-cycle parameters, performance areas, or impact categories. Commonly cited elements are energy, water, materials, waste, and health. Another is siting, particularly with respect to transportation, ecology, and smart growth. The siting element has increased in prominence over the last several years as more attention has focused on the built environment beyond the building itself. Most descriptions do not explicitly include a serviceability, productivity, or functionality element, but that may be because those would be commonly expected to be integral elements of any building design. However, they are included explicitly among the objectives for high-performance buildings, which may also consider such others as disaster and climate resilience. These objectives have risen in prominence in the wake of a number of high-profile natural disasters, including Hurricanes Katrina and Sandy, and the 2011 earthquake and tsunami that initiated the Fukushima Daiichi nuclear meltdown. The goals of a given green building project may vary depending on the needs of the stakeholders, including a building's expected occupants. As a result, different elements may be prioritized in different projects (see " Net-Zero Buildings ," below). Local factors such as climate zone and flood risk may influence the design process in ways that affect the relative emphasis placed on the various elements discussed below. A reduced energy footprint is probably the most widely cited element of green building. Techniques include energy efficiency and conservation, through such means as energy-efficient appliances and lighting, weatherization, and daylighting; use of alternative, renewable sources of energy, such as solar or geothermal power or combustion of biomass; utilization of energy storage technologies, often in combination with on-site renewable energy generation; and participation in smart-grid innovations such as demand-response programs. Energy is widely considered a crucial element because of the economic costs and environmental impacts associated with energy use. A 2010 study by the National Academies found the potential energy savings from widespread deployment of energy efficiency measures to be significantly higher for buildings than for transportation and industry. In a 2015 report on energy technologies, the Department of Energy estimated that buildings using the best available energy efficiency technologies would consume about half as much energy on average as those in the current building stock. Federal law sets numeric requirements for reductions in energy use by federal buildings. The energy intensity of such buildings declined by more than 22% from 2003 to 2015. Nevertheless, 2015 consumption exceeded the federal goal. Given its importance, energy is sometimes mistakenly treated as the predominant or even the sole element to be considered in green building. However, while a green building almost always addresses the energy element, a building that focuses solely on energy may not be a green building: It could have other environmental impacts that outweigh any benefits from its reduced use of energy. Reducing water usage in buildings can provide cost savings. It can also aid management of water resources, especially in arid areas and in response to periodic drought elsewhere. Reductions can be achieved through such measures as reduced-flow plumbing fixtures, recycling of wastewater, and landscaping designed to reduce irrigation requirements. Water management may also include how the building and associated land handle rain, on-site water, and run-off. Development designed to ensure that the way a site handles water is similar to how it did so before development is called low-impact developmen t , which "uses natural and engineered infiltration and storage techniques to control stormwater where it is generated." Among the methods used are reduction in impervious surfaces through landscaping, use of porous materials and green roofs, and use of holding ponds, swales, rain gardens, and similar measures. Such techniques for water management are sometimes referred to collectively as green infrastructure (see the section on " Environmental Protection Agency "). The materials used in a building, during both construction and operations, can contribute substantially to the building's environmental footprint. The choice and use of materials affects resource depletion, pollution, embodied energy, and health. "Environmentally preferable" or "green-labelled" products can reduce the impact. Such materials may have significant recycled content, be made from renewable biological resources (so-called "biobased" products), or be created with processes that use low amounts of energy and produce low amounts of pollutants. They may also be designed to reduce health risks such as those from formaldehyde and other volatile organic compounds (VOCs). There is some debate about what constitutes an environmentally preferable material. The lack of a consistent vocabulary for describing the sustainability attributes of materials, as well as inconsistencies in the measurement methodologies and reporting frameworks used by various eco-labelling systems, can make it difficult to determine whether a given material is preferable to a substitute. The environmental impacts from a building's waste stream over its life cycle can be mitigated by waste-reduction efforts, which fall broadly into four main categories: source reduction, reuse, recycling, and waste-to-energy. The waste from standard demolition and construction processes can be reduced through more efficient use of materials (source reduction) and recycling or reuse of waste products. Landscaping can be planned to reduce or eliminate chemical pollutants from grounds maintenance and to recycle waste such as lawn clippings through mulching and composting. High-efficiency boilers and furnaces can reduce the production of many atmospheric pollutants. Operational solid waste such as paper and foodstuffs can be recycled or otherwise processed to reduce their environmental impact. Several factors can influence the health impacts of buildings. For some, the health effects are obvious, such as the presence of indoor air pollutants like mold, radon, carbon monoxide, asbestos, and VOCs. Indoor air quality (IAQ) has a significant impact on occupant health, given that most people tend to spend a large percentage of each day indoors. Primary techniques for maintaining high IAQ include ensuring adequate ventilation; providing air filtration; and using materials without heavy metals, VOCs, asbestos, or other potentially toxic substances. Overall indoor environmental quality (IEQ) includes, in addition to IAQ, factors such as lighting, climate control, acoustics, and ergonomic design; those may also have significant impacts on the health of building occupants. Where a building is situated can have significant effects on its environmental footprint. For example, siting of buildings near transportation hubs can facilitate the use of public transportation and reduce impacts from private automobiles. Site selection may also take into account the ecological sensitivity of potential sites, to minimize adverse impacts on ecological services and native species of plants and animals. The orientation of building axes and surfaces, and the building's proximity to trees and other plantings, affect its heating and cooling requirements. Climate-related risk factors may also be incorporated into siting decisions. Risks from sea-level rise, flooding, and extreme weather events, all of which may be affected by climate change, are of increasing concern to builders, particularly in coastal areas. A building that is not useful to its occupants is unlikely to be worth its cost, no matter how small its environmental footprint. Therefore, productivity and other measures of utility comprise an important element of green building that is not always discussed. A large percentage of U.S. workers spend their days in offices, and studies have suggested that IEQ strongly influences worker comfort and productivity. There is some evidence that green buildings can lead to improved productivity among occupants. However, that is not always the case. For example, poor acoustic performance has been repeatedly observed in certified green buildings, suggesting that trade-offs do sometimes occur between serviceability and other elements. While serviceability is not generally considered as a separate element in green-building design, it is explicitly identified as an objective for high-performance buildings and has received increasing attention in green certification systems. Resistance to hazards such as earthquakes, hurricanes, flooding, subsidence, and forest fires can increase the useful life of a building and permit it to function when services such as transportation and utilities are not available. Approaches to resilience include such practices as resistant construction; locating critical mechanical components on upper levels away from potential flood waters; on-site power generation, such as through photovoltaic and wind-turbine technology; rainwater harvesting; and water recycling capabilities. An increasing emphasis has been placed on climate-resilient design, defined in Executive Order 13693 as assets designed to "prepare for, withstand, respond to, or quickly recover from disruptions due to severe weather events and climate change for the intended life of the asset." One of the most salient features of green building is integration. The green building approach considers integration across (1) elements, in order to improve performance in multiple impact areas, and (2) stages, in order to minimize environmental impacts throughout the building's lifecycle. This approach, with its focus on the whole building (see " Whole Building Design Guide ," below), can lead to better assessment of the overall environmental impact of a building. It also permits explicit assessment of and balance among potentially competing goals, and it allows planners to examine how different elements and stages interact and to develop an integrated strategy. Integration and performance with respect to several elements can be enhanced by the appropriate use of information technology in building operations (see " Smart Buildings and the Internet of Things ," below). A focus on one element at the expense of others can be counterproductive. For example, energy efficiency can be improved by sealing the building envelope to prevent conditioned air from escaping. But an absence of air exchange can result in increased concentration of pollutants in the building and can impede moisture control, fostering the development of mold and deterioration of building materials. Addressing both energy efficiency and health requires either a compromise or technologies such as active ventilation with heat exchange. A green building approach reduces the risk of unanticipated problems by forcing an examination of how actions affecting each element impact others, so that an overall optimization can be achieved. Nevertheless, in some cases, such as many renovations, only one or a few factors might be feasible to address. In other cases, it may make sense to prioritize certain elements at the expense of others due to cost or feasibility constraints, local environmental factors, or occupant priorities. A focus on only one stage in the life cycle of a building can lead to savings at that stage but losses at another. For example, in the absence of sufficient data on the environmental impacts of developing, manufacturing, installing, using, and eventually disposing of alternative building materials, a choice that appears to be environmentally sound may in fact not be. Use of concrete walls provides more insulation on average than use of wood, but has much higher net emissions of carbon dioxide over its life cycle. Far more energy is used in operating a building than in constructing one, however, so choices made during construction may need to be balanced with planning for the postoccupancy stage. A green building approach can reduce such problems by facilitating an assessment of the impact from actions at one stage on all the others. Many elements are also clearly interdependent. For example, use of environmentally preferable products can affect occupant health, which in turn can affect productivity. A building with on-site renewable energy generation may be well-prepared to function during periods when power is unavailable from utilities, such as after a natural disaster. On-site stormwater management can facilitate the provision of ecological services. Formal systems and tools have been developed over the last few decades that set criteria for green and sustainable buildings and methods for assessing whether new construction or renovation projects meet those criteria. The systems and tools fall into one or more of four main categories: rating systems, certifications, standards, and codes. Given the range and interconnections of elements involved, determining whether a building is green or sustainable is not straightforward—there is no simple metric for determining how well a building meets the desired criteria. To address this problem, in the 1990s, some professional organizations in the building sector developed rating and certification systems that helped to standardize and define green building practices and raised public awareness of them. The term rating system is often used interchangeably with certification system , although they refer to somewhat different concepts. Many systems, such as the well-known Leadership in Energy and Environmental Design (LEED), combine both rating and certification into a single system. Rating systems assign points to buildings for meeting established criteria in various green building design categories. That results in an overall score and, often, assignment to one of a number of ranked tiers indicating the level of rigor of the criteria a building attains. Certification provides validation that a building meets or exceeds specified design or performance requirements. It is arguably most objective when an independent entity conducts the assessment and awards the certification. Such a third party must be independent of the builder, contractor, and designer, as well as the organization that developed the rating system or standard. A handful of organizations currently offer rating and certification for green buildings. By far the most prevalent certification system within the United States is LEED, developed by the U.S. Green Building Council (USGBC). When it launched in 1998, LEED was among the first voluntary, consensus-based certification systems in the United States. It quickly became widely recognized as a benchmark for green building design. The number of LEED certifications has increased annually since the first certification was awarded in 2000. As of April 2017, more than 37,300 commercial buildings had been certified by LEED worldwide. USGBC has also expanded the categories of building certifications offered to include new commercial construction, existing buildings, building interiors, homes, schools, retail, healthcare, whole neighborhoods, and others (see textbox on " Special-Use Buildings "). Certification is also available for operations and maintenance of existing buildings (including buildings first certified when new), with a five-year recertification cycle. LEED focuses primarily on six green building elements: location and transportation, sustainable sites, water efficiency, energy and atmosphere, materials and resources, and indoor environmental quality. It also has credit categories for innovation and for regional priority, which considers specific factors of importance to sustainability within a specified region. To be LEED-certified, a building must meet a set of mandatory basic requirements for most elements and must also receive a designated number of the total points that can be earned within each element from optional items. A building's total score determines its level of certification: Certified, Silver, Gold, or Platinum. While this "checklist" approach has been criticized, it permits comparatively simple assessment of compliance and can facilitate the kind of integrated consideration of elements that many observers regard as a hallmark of green building. The LEED rating system is updated periodically; the most recent version, LEED v4, was released in November of 2013. Other rating and certification systems in use in the United States include the following: The Building Research Establishment Environmental Assessment Method (BREEAM) is a British system developed in 1990. Though BREEAM rating systems have been used internationally since then, only the BREEAM In-Use certification has been introduced in the United States, beginning in 2017. BREEAM In-Use is an online rating system for existing commercial building performance. Unlike LEED, BREEAM In-Use has no prerequisites; any existing building can use it to benchmark performance and certify subsequent improvements. BREEAM ratings are Acceptable, Pass, Good, Very Good, Excellent, and Outstanding, which are signified by between one and six stars. Rating levels are based on a building's score across nine impact categories: management, health and well-being, energy, transport, water, materials, waste, land use, and ecology and pollution. To remain valid, certifications must be renewed annually. Green Globes was developed in Canada by the Green Building Initiative. It is based on BREEAM, and has an associated standard (see " Green Building Codes and Standards "). A building may earn between one and four Globes based on the number of points earned out of a possible total of 1000. Points are distributed across six elements—site, energy, water, materials and resources, emissions, and indoor environment—plus project management. Like BREEAM In-Use, Green Globes has no mandatory provisions or prerequisites that must be met before certification can be considered; certification and rating level are based solely on the number of points earned. The International Living Future Institute's Living Building Challenge offers three certifications: Living Building Certification, Petal Certification, and Zero Energy Building Certification. Criteria for certification fall into seven performance areas, referred to as "Petals": place, water, energy, health and happiness, materials, equity, and beauty. Living Building Certification requires a building to meet requirements in all seven performance areas. Petal Certification requires compliance with no fewer than three of the seven Petals, one of which must be water, energy, or materials. Zero Energy Certification requires a building to generate all of its energy needs on site without using combustion. Unlike new-building certification under the other ratings systems, which occurs upon completion of construction, certification under the Living Building Challenge also requires a 12-month assessment of actual building performance. Different ratings systems emphasize different aspects of green building. Therefore, whether one or another is more appropriate may depend on local conditions and priorities. Systems also differ in the types of buildings for which they offer guidelines and certification; some focus primarily on new construction, while others are more geared toward existing buildings. In addition to the comprehensive green certification systems discussed above, some additional programs exist to certify that a building has taken steps to improve environmental performance for a single element or in a limited number of performance areas. These include Energy Star (energy-efficiency), Indoor airPLUS (indoor air quality), WaterSense (water efficiency), Zero Energy Ready Home (energy and air quality), and Passive House/ PHIUS+ (energy, water, and air quality). In many cases, a building may be separately certified under more than one of those programs. Several federal statutes and policies impose green building requirements on federal offices and agencies, and some agencies have been using third-party green building certification systems since the late 1990s. While no certification system meets all of the federal requirements for green buildings, the General Services Administration (GSA) has recommended that agencies use third-party green certification systems, and some federal agencies have found the use of third-party certification systems to have benefits that include simplifying compliance with federal guidelines, reducing the need for additional staff, and providing a recognizable label to communicate sustainability efforts within the agency and to the public. Several agencies have elected to establish internal policies on certification under one of the available rating systems. EISA required the Secretary of Energy, in consultation with GSA and the Department of Defense (DOD), to identify a third-party certification system and level that the Secretary "determines to be the most likely to encourage a comprehensive and environmentally-sound approach to certification of green buildings" (42 U.S.C. §6834(a)(3)(D)(i)(III)). The Secretary's recommendation is to be reviewed and updated every five years, taking into account the results of a study to be conducted by the Director of GSA's Office of Federal High-Performance Green Buildings, which was also established by EISA (42 U.S.C. §17092). As of 2013, GSA recommended that federal agencies use either LEED or Green Globes, and that agencies using one of these systems should achieve either a LEED Silver rating or Two Globes under the Green Globes system for new construction and major renovation projects. Instead of specifying a particular rating system, the 2014 Department of Energy rulemaking on green building certification sets out minimum criteria for a rating system to be eligible for use by federal agencies. Those agencies choosing to pursue third-party certification must choose a system that meets those criteria. In addition to federal policies, many states require green building certification or the equivalent for government buildings, and many cities or counties have such requirements for buildings in the commercial sector. Some jurisdictions also provide grants or tax incentives for some green building certifications. Green building rating and certification systems have served as testbeds for objectives and practices that have subsequently been incorporated into model building codes and standards. Unlike rating and certification systems, building codes are often mandatory. While most standards are not themselves mandatory, they, along with model codes, may be incorporated into mandatory codes or laws. This section discusses comprehensive green building codes and standards that address multiple green building elements. Codes and standards dealing solely with energy efficiency are not discussed. Building codes specify minimum requirements for building design and construction. Historically, they have focused primarily on health and safety, but they can cover many other aspects of a building's design or construction, from aesthetics to resource use. The " Energy Policy Act of 1992 " (EPACT 1992) established a baseline for energy efficiency in building codes. Beyond such federally mandated minimum requirements, it is left to state and local governments to determine the contents of the codes that regulate buildings within their jurisdictions. Rather than create and revise their own codes, however, many state and local jurisdictions adopt or modify national model codes generated by code development organizations. Green building codes specify additional requirements for environmental design and performance that go beyond, and, in some cases, can be layered on top of existing building codes. They are occasionally referred to as "beyond-code" or "above-code" options, because they exceed minimum building code requirements. Governments adopting green building model codes can choose to make them mandatory or treat them as voluntary measures for meeting green building objectives. Both model codes and mandatory building codes often incorporate technical standards for specific components or features. Those standards are created by recognized standards development organizations (SDOs). Some such organizations have used the standards-development process to create more general green building standards. The Whole Building Design Guide defines a standard as "a set of guidelines and criteria against which a product can be judged." Just as a building may be certified under a rating system, a building that has achieved a given standard may be certified as having met the criteria of that standard. For both green building codes and standards, specific requirements may be achievable by multiple pathways. Prescriptive pathways specify the precise method of achieving a given requirement, whereas performance pathways allow designers flexibility in their methods provided that the projected or modelled end results meet the necessary requirements. A newer option is outcome-based requirements, which establish a performance target that must be met and verified through measurement and reporting after construction ends. Green building standards are sometimes described as code-intended, indicating that they are written in mandatory, code-enforceable language, and may be adopted by jurisdictions, either as they are written or with modifications made by the adopting entity. Both codes and standards are developed through a consensus process that involves multiple stakeholders, but SDOs typically require accreditation by a body such as the American National Standards Institute (ANSI), ensuring that their development process adheres to a set of approved procedures. ANSI standards also require that certification be performed by a third party. There are two main developers of national green building model codes and standards in the United States: the International Code Council (ICC) and ASHRAE. Their efforts are discussed below. The ICC is responsible for the development of a comprehensive family of integrated International Codes, covering a number of building sectors. The ICC International Building Code (IBC) is widely used in the United States. In 2012 the ICC released the International Green Construction Code (IgCC), described as "the first model code to include sustainability measures for the entire construction project and its site." The IgCC functions as an overlay code, meaning that it is fully compatible, and can be adopted in conjunction with, the full family of ICC codes governing building safety and other features. The most recent revision was released in 2015. Municipalities choosing to adopt the IgCC as an overlay may choose from among various compliance pathways and options in order to make the mandated requirements more or less strict, as well as to account for local climate and other pertinent factors. The IgCC covers most building types, with the exception of low-rise residential buildings. The IgCC refers low-rise residential builders to the ICC 700 National Green Building Standard (NGBS), an ANSI standard developed in partnership with ASHRAE and the National Association of Homebuilders (NAHB). The NGBS is structured as a rating system, much like LEED, but can be adopted by ordinance, much like a model code. ASHRAE, USGBC, and the Illuminating Engineering Society of North America (IES) have also jointly released a high-performance green building standard for nonresidential buildings and residential buildings of more than three stories. Known as Standard 189.1, it functions as a code-intended standard and is offered as a compliance option under the IgCC. The standard contains requirements in the following areas: site sustainability, energy efficiency and renewable energy, water-use efficiency, indoor environmental quality, and building impacts on the atmosphere, materials, and resources. Elements of Standard 189.1 have been incorporated into the building requirements for Department of Defense properties. In 2015, the ICC and ASHRAE announced a partnership to fully integrate Standard 189.1 to serve as the technical content of the 2018 version of the IgCC. The new code will also be aligned with the LEED rating system, providing the market with a streamlined set of beyond-code tools. In addition to such national efforts, several state, local, and tribal authorities have developed their own green building codes. Several federal laws, executive orders, and other policy instruments have provisions relating to green building. Selected relevant provisions are described below. However, the list presented in this report is not exhaustive. For example, the Resource Conservation and Recovery Act of 1976 (RCRA), as amended (42 U.S.C. §6901 et seq.), requires agencies to procure products with recycled content. This report also does not include discussion of state and local policies, which have substantial influence on green building efforts within those jurisdictions. The Energy Policy Act of 1992 ( P.L. 102-486 ), known as EPACT 1992, contained incentives and requirements relating to efficient use of energy and water in federal, commercial, and residential buildings. It included, among other matters, provisions relating to state building energy codes, energy efficiency in federal buildings and public housing, a pilot program for mortgages for energy-efficient housing, the development of energy-efficient technologies, and energy and water efficiency requirements for appliances, plumbing fixtures, and building materials. Among other provisions, the Energy Policy Act of 2005 ( P.L. 109-58 ), known as EPACT 2005, required the development of energy and water conservation programs for congressional buildings and a reduction in energy consumption by federal buildings of 20% (relative to 2003) by 2015; promoted the procurement of energy-efficient products by federal agencies; established a testbed program for advanced building efficiency; set an energy consumption target for new federal buildings of 30% below existing standards; and required the application of sustainable-design principles to new and replacement federal buildings. It also continued authorization of DOE's weatherization assistance program. The act set an improvement goal of 25% by 2012 from a 1990 base for state energy conservation plans. It also authorized funding for states to administer rebate programs for residential energy-efficient appliances, to assist local governments in improving energy efficiency in public buildings, and for other state activities, including incentives to states to establish building energy-efficiency codes that meet or exceed established standards. It established the Energy Star labeling program as a joint program of DOE and EPA, and established public information and education programs relating to energy conservation. It also set energy and water conservation standards for various specific products. The act requires agencies to purchase products that either have an Energy Star label or are designated as energy-efficient by the Department of Energy. EPACT 2005 set energy-efficiency standards for public housing and directed the Department of Housing and Urban Development to develop a strategy for energy conservation and efficiency. The act also provided various tax incentives to businesses and individuals for energy and water efficiency. The Energy Independence and Security Act of 2007 ( P.L. 110-140 ), known as EISA, provided both a general legislative framework for federal green building efforts, including a definition of high-performance green building (see " Definitions of Green Building ," above), and specific actions and requirements. Titles III, IV, and V relate most specifically to green building. Title III set efficiency standards for various appliances and electric lighting. It also required the use of energy-efficient lighting in facilities leased by GSA and further directed that such facilities adhere to energy efficiency and renewable energy requirements to be set by the agency. Title IV has provisions relating to residential, commercial, federal, and certain other kinds of buildings: Residential. The act increased funding for DOE's program to provide assistance to low-income families for weatherization of residences, to improve energy efficiency. It required a feasibility study by DOE of the unfunded state rebate programs for energy efficiency and renewable energy that EPACT 2005 had authorized. It also established energy-efficiency standards for manufactured housing such as mobile homes. Commercial. The act required DOE to create an Office of Commercial High-Performance Green Buildings to facilitate the development of green commercial buildings, including zero-net-energy buildings, in partnership with other federal and with nonfederal entities. Federal. EISA increased the overall rate of required reduction in total energy consumption of federal buildings in each agency, from 20% (relative to 2003) to 30% by 2015. It set more stringent energy goals for new construction and major renovations, requiring them to reach a 65% reduction by 2015, and zero-net energy use by 2030; and it required the identification and use of a green building certification system for such structures. It also set general water-conservation guidelines and stormwater runoff requirements for property development. Agencies are required to ensure that new building equipment implementing the above measures is commissioned to be operating at design specifications, to plan for operations and maintenance of equipment, and to measure energy and water savings. Agencies were also directed to install advanced metering devices in federal buildings and to record and report energy use data for metered facilities into a building energy benchmarking system. Federal buildings must undergo regular evaluations of energy and water use, with the Office of Management and Budget (OMB) issuing scorecards twice per year on agency performance in energy management. The life cycle over which energy costs are assessed was extended from 25 to 40 years. Any new major equipment installed must be energy efficient, and the act accelerated the use of energy-efficient lighting and other cost-saving technologies in GSA facilities. Any buildings leased by a federal agency must have a recently earned Energy Star label. The act also established an Office of Federal High-Performance Green Buildings within GSA to coordinate and facilitate the development of such buildings in the federal sector. GAO is to perform audits of implementation of these requirements. Other . The act contains provisions to facilitate the greening of schools, with emphasis on environmental health and energy efficiency. It also authorized energy-efficiency assistance for state and local public facilities and institutions of higher learning. It required the Department of Housing and Urban Development to use updated energy-efficiency standards for public and assisted housing. It also established green building research and demonstration projects through GSA, DOE, and EPA. Title V contains energy-efficiency provisions relating to the U.S. Capitol complex, and amended provisions in law relating to energy savings performance contracts. It also specified certain actions to promote energy efficiency at executive branch agencies and in the supply of electricity and natural gas by utilities, and for state and local governments to develop and implement strategies for energy efficiency and conservation. Other relevant provisions in the law include authorization of research and development (R&D) relating to energy efficiency and renewable energy, and loans and other activities to help small businesses improve energy efficiency. The American Recovery and Reinvestment Act of 2009 ( P.L. 111-5 , ARRA) provided $4.5 billion to convert GSA facilities to high-performance green buildings. It also provided $250 million to the Department of Housing and Urban Development (HUD) for green retrofits of housing. It permitted states to use a portion of provided education funds for green renovations of public schools. It also provided funds to various agencies for energy-efficiency improvements to buildings. The Energy Efficiency Improvement Act of 2015 ( P.L. 114-11 ) directs GSA to develop model leasing provisions to encourage the implementation of energy and water efficiency measures by tenants in commercial buildings. GSA may use those provisions for leases involving federal agencies, and it must make them available to state and local governments for their own use. The act also amended EISA to add provisions regarding improving energy efficiency in tenant spaces. These include directing DOE to study the feasibility of improving energy efficiency in commercial buildings through the implementation of energy-efficiency measures in discreet spaces within those buildings; directing the DOE's Energy Information Administration to collect additional occupant energy-use information as part of its Commercial Buildings Energy Consumption Surveys; and directing EPA to develop a Tenant Star recognition label as a part of the Energy Star program. The act also contains provisions related to the establishment of energy conservation standards for grid-enabled water heaters used as energy storage or demand-response assets, and energy efficiency benchmarking requirements for federal agencies leasing space in buildings without an Energy Star label. DOE is also directed to study the impact of state and local performance benchmarking policies on commercial and multifamily buildings and maintain a public database of energy-related information on such buildings. In 2015, President Obama signed Executive Order (E.O.) 13693, Planning for Federal Sustainability in the Next Decade . The order revoked and replaced previous Executive Orders 13423 and 13514, which established green building as a key component of federal efforts to reduce environmental impacts, improve resource use efficiency, and lower operating costs at federal facilities. E.O. 13693 expanded upon the sustainability goals of the previous orders and set new targets for federal agencies to achieve by FY2025. Targets include requiring each agency to reduce building energy intensity by 2.5% annually relative to FY2015, reduce potable water consumption intensity by 36% relative to FY2007, produce at minimum 25% of total building electric and thermal energy from clean sources, and ensure that all new buildings with more than 5,000 gross square feet of floorspace are designed to achieve net-zero energy, and, if possible, net-zero water or waste by FY2030. The order also called for the inclusion of climate-resilient design elements in federal buildings, and directed the Chair of the Council on Environmental Quality (CEQ) to issue revised " Guiding Principles for Federal Leadership in High Performance Sustainable Buildings ." E.O. 13693 directed agencies to ensure that, for federal buildings of more than 5,000 square feet in area, all new ones and at least 15% (by FY2025) of existing ones comply with the Guiding Principles, with the ultimate goal of achieving compliance in the entire inventory. According to a GSA analysis, agency efforts to comply with E.O. 13693 led to an 18% increase in the number of federal sustainable buildings between FY2014 and FY2015. In 2006, representatives of 19 federal agencies and offices signed a memorandum of understanding (MOU) titled "Federal Leadership in High Performance and Sustainable Buildings." The MOU was developed concurrently with the enactment of EPACT 2005 and contained the first set of five core Guiding Principles for federal high performance and sustainable buildings: employ integrated design principles, optimize energy performance, protect and conserve water, enhance indoor environmental quality, and reduce environmental impact of materials. Subsequent revisions of the Guiding Principles were issued in 2008 and, most recently, in 2016 to reflect progress in green building design and to address a broader set of issue areas, including the health and productivity of building occupants. It also added a sixth overarching principle to the list: assess and consider climate change risks. See " Guiding Principles " textbox for more detail. The federal government owns or leases about 273,000 buildings in the United States, comprising nearly 3 billion square feet in floorspace ( Table 1 ) and costing nearly $6.1 billion in energy bills. EISA and other policy instruments require all federal agencies to implement green building practices for buildings they control. Several federal offices provide guidance and support for the implementation of those requirements. Except for GSA and DOD, which together control three-quarters of all federal building floorspace, this report does not discuss green building within individual agencies, although such efforts may be significant. However, several agencies have programs and activities that have a broader focus than reducing the environmental impacts of the facilities of that agency. This section of the report discusses selected examples. The General Services Administration (GSA) manages about 425 million square feet of space in over 8,500 buildings, providing workspace for over 1.2 million federal workers. In 2010, the agency announced that it would require all GSA-owned new construction and major renovation projects to be LEED-certified at the Gold level or above. Properties that GSA leases on behalf of another agency may be either LEED or Green Globes certified at the Silver or Two Globes levels, respectively. By 2020, GSA says that all new buildings will be designed to achieve net-zero energy, water, or waste, exceeding the timeframe and requirements of Executive Order 13693. GSA's Green Proving Ground program conducts evaluations of next-generation building technologies and recommends those that meet agency standards for deployment throughout GSA's property holdings. Several offices contribute to GSA green building efforts, including the Energy Program, Environment Program, Leasing Program, Office of Design and Construction, and the Office of Federal High-Performance Green Buildings. EISA required GSA to establish the Office of Federal High-Performance Green Buildings, to coordinate activities relating to such buildings across federal agencies (42 U.S.C. 17092). The office delivers actionable information to improve building performance and conducts assessments on existing green buildings. It created and maintains the Sustainable Facilities Tool (SF Tool), an interactive website supplying green construction, purchasing, and operations resources and information to federal agencies and other interested parties. Much of the research and recommendations generated by the office's other programs are made available on the SF Tool website. The Facility Management Institute is another GSA initiative intended to assist agencies in improving the operations and management of federal buildings. GSA has several green-building programs and projects that are the result of collaborations with other agencies and offices. EISA (Sections 433 and 436) directed the Director of the Office of Federal High-Performance Green Buildings to provide recommendations to the Secretary of Energy on rating and certification systems that can be used by agencies for meeting federal green building requirements, based on the results of a study to be conducted by the office every five years (42 U.S.C. §6834(a)(3); 42 U.S.C. §17092). The office must also coordinate with the Department of Energy on commercial high-performance green building activities under EISA. GSA and DOE cochair the Interagency Sustainable Working Group, which is tasked with reporting on agency progress toward the goals laid out in E.O. 13693. GSA participates in climate adaptation planning for buildings as part of the Agency Adaptation Planning Working Group, which is a subgroup in the Interagency Climate Change Task Force. GSA was also a leader in the interagency effort to develop sustainable design principles for the federal government, culminating in the development of the Whole Building Design Guide. GSA has also collaborated with the Department of Health and Human Services and New York City agencies to develop FITWEL, a voluntary certification program to promote occupant health and wellness through the design of workplaces. Most of the external green building activities of the Department of Energy (DOE) relate to the energy element (see " Elements of Green Building "), through the Building Technologies Office (BTO), the Federal Energy Management Program (FEMP), and the Weatherization and Intergovernmental Programs Office (WIP) of the Office of Energy Efficiency and Renewable Energy (EERE). BTO sponsors and performs R&D to improve both commercial and residential energy efficiency. It is also involved in the development of energy codes and enforcement of appliance and equipment standards, transfer of relevant technologies to the marketplace, and integrated design of energy-efficient buildings. According to BTO's Multi-Year Program Plan for 2016-2020, the office's long-term goal is to achieve a 50% reduction in energy use intensity in commercial and residential U.S. buildings compared to 2010 levels. A major focus for the program in the next several years will be on enabling the development of cost-effective net-zero energy buildings for the residential and commercial sectors. BTO has several notable programs, including the following: Building America is an R&D program in partnership with the building industry. It focuses on a whole-building, integrated approach to improving energy savings in residential buildings. The Commercial Buildings Integration program implements initiatives related to energy savings in commercial buildings, including improving building design, accelerating market adoption of high-efficiency technologies, and increasing access to building performance data. The Better Buildings Alliance is a public-private partnership that promotes energy efficiency in commercial buildings through collaboration with members of the U.S. commercial building community. Energy Star is a joint program with EPA that uses voluntary labeling to promote energy-efficient products. Zero Energy Ready Home is a recognition program that builds on the requirements of Energy Star and EPA's Indoor airPLUS program to recognize builders that achieve a minimum energy efficiency improvement of 40% over the average new home. The Building Performance Database provides public access to data on the energy performance of commercial buildings. The Federal Energy Management Program (FEMP) assists federal agencies in implementing energy savings and management, including the designation required by EPACT 2005 of energy-efficient products for purchase by agencies. It provides assistance with procurement, construction, operations, and maintenance. It also chairs, along with the GSA, the Interagency Sustainability Working Group, which is responsible for assisting agencies in implementing sustainable building design, including technical guidance for implementation of the sustainable buildings requirements in E.O. 13693. FEMP collects data and issues reports annually on energy consumption by agencies and on related topics. Among other DOE entities, the Energy Information Administration (EIA) collects and reports on data relating to energy, including that used by buildings, most notably the residential and commercial energy consumption surveys. Some of DOE's national laboratories also perform R&D relating to green buildings. The Advanced Research Projects Agency-Energy (ARPA-E) funds R&D for early-stage energy-related technologies, including several projects focused on developing innovative, energy-efficient heating and cooling systems for buildings. The Environmental Protection Agency (EPA) has a broad range of programs and activities relating to one or more of the main elements of green building. Notable programs and activities include the following: Energy. EPA originated the Energy Star program. The Energy Star Portfolio Manager can be used to measure, track, and benchmark building energy use. The agency's Green Power Partnership supports the procurement of power from renewable resources by government and private-sector organizations. Water. EPA administers WaterSense, a voluntary labeling program established in 2006 to promote water efficiency. Manufacturers may earn WaterSense labels for their products, and landscape-irrigation professionals can be certified under the program. WaterSense-labelled homes and products are independently certified to be at least 20% more water efficient than average. The Green Infrastructure Collaborative and related activities promote community adoption of green infrastructure, a stormwater management approach that uses vegetation, soils, permeable pavements, and other practices to reduce stormwater runoff and maintain or restore natural water filtration and storage in built environments. Materials and Waste . The Sustainable Materials Management Program (SMM) encourages a life-cycle materials management approach that seeks to reduce environmental and human health impacts associated with materials use, from extraction to disposal. SMM provides resources for governments and businesses on assessing and reducing material use, purchasing recycled materials, and increasing recycling and reuse of construction and demolition materials. SMM programs include WasteWise, a public/private partnership in which participants set goals and report progress on preventing waste, expanding recycling, and increasing purchasing of recycled materials; and the Federal Green Challenge, which encourages government agencies to reduce their waste footprint and water usage, among other goals. The Environmentally Preferable Purchasing (EPP) Program assists federal agencies in meeting green purchasing requirements. The Comprehensive Procurement Guideline program identifies recycled products that comply with RCRA requirements. Health. EPA supports activities such as R&D and awards programs to develop safer and more environmentally friendly chemicals, including "green chemistry" technologies. The Indoor Air Quality Program provides information and tools to ensure the protection of indoor environmental quality in schools, residences, and commercial buildings. Indoor airPLUS is a voluntary partnership and labeling program that specifies minimum air quality design features for homes. Siting. The Smart Location Database is a nationwide geographic data resource that measures neighborhood characteristics such as housing density, neighborhood design, and transit accessibility to produce a measurement of a location's siting efficiency. The agency also has a variety of programs and activities relating to smart growth and sustainability. EPA has also published resources on implementing green building policies for local governments and tribal communities. The Department of Defense (DOD) has the largest building footprint in the federal government ( Table 1 ) , with a portfolio that contains more than 276,000 buildings covering 2.2 billion square feet and located across thousands of sites worldwide. DOD issues its own requirements for Department-owned buildings and facilities under the Unified Facilities Criteria (UFC) program. UFC documents contain technical criteria and standards relating to the planning, design, construction, operations, and maintenance of DOD facilities. Two recently issued UFC documents contain requirements relating to green building: UFC 1-200-02 High Performance and Sustainable Building Requirements (2016) provides guidance toward complying with the minimum building requirements for federal buildings established by EISA, EPACT 2005, the Guiding Principles, and E.O. 13693. All new construction and major renovations must comply with these criteria. UFC 3-210-10 Low Impact Development (2016) provides guidance for complying with EISA provisions governing stormwater management by using low-impact development (LID) techniques aimed at infiltrating and storing stormwater in order to restore site hydrology and mitigate adverse effects of runoff. DOD also sets and reports on a variety of goals aligned with green building objectives through the annual publication of its Strategic Sustainability Performance Plan (SSPP). The update for SSPP FY2016 lists department-wide goals for reducing use of facility energy and potable water, stormwater management, solid waste diversion, construction and demolition debris diversion, and increasing the percentage of high performance sustainable buildings. Some of the service branches of DOD have created their own branch-wide green building goals and initiatives. The Army issued a directive in 2014, expanding a Net Zero Installations pilot project into an Army-wide initiative. The Air Force uses Sustainability Development Indicators to ensure that installation development plans consider a wide range of environmental impact areas and performance elements. In December of 2016, DOD and EPA signed a Memorandum of Understanding listing, among others, goals to work together to implement sustainable and resilient military installations, promote a sustainable and resilient natural and built infrastructure, and to engage DOD installations as test beds for innovative technologies. The position of Federal Chief Sustainability Officer was originally established under the title of the Federal Environmental Executive in 1993 by Executive Order 12873. Executive Orders 13423 and 13693 broadened that position to include an Office of the Federal Environmental Executive, later renamed the Office of the Chief Sustainability Officer, and extended the duties to include assisting and monitoring the implementation by agencies of the order, including its green building requirements, and advising the Council on Environmental Quality. The green building efforts of the National Institute of Standards and Technology (NIST) are housed in NIST's Engineering Laboratory. The Sustainable and Energy-Efficient Manufacturing, Materials, and Infrastructure Program focuses on improvements in measurement science and data relating especially to intelligent building systems, sustainably engineered materials, and achieving net-zero energy buildings with high indoor air quality. A component of this program is the Net-Zero Energy High-Performance Buildings Program, which is focused on developing building metrics for overall building sustainability and reducing building energy usage through improvements in specific component areas. The Net-Zero Energy Residential Test Facility (NZERTF), developed under this program, is a laboratory and demonstration facility dedicated to the development of measurement science needed to achieve net-zero energy homes. NIST has also developed Building for Environmental and Economic Sustainability (BEES), a software tool that uses life-cycle assessment methods to facilitate the selection of environmentally preferable building products. NIST has also helped to add resources on climate resiliency for buildings to the U.S. Climate Resilience Toolkit, through participation in the Community Resilience Panel for Buildings and Infrastructure Systems, which it cosponsors. The Department of Housing and Urban Development (HUD) administers several mortgage insurance and home-financing programs that contain provisions intended to encourage the adoption of green building elements in public housing. The Mark-to-Market program is an initiative that restructures HUD-insured mortgages for multifamily housing projects. A component of the program offers financial incentives for green building measures to be incorporated into eligible housing projects. The Federal Housing Administration (FHA) administers the Energy Efficient Mortgage Program, a program intended to enable homeowners and buyers to finance the cost of energy-efficiency improvements through their FHA-insured mortgage. The Public Housing Capital Fund and the Public Housing Operating Fund provide funding to Public Housing Agencies that may be used to make energy and water efficiency improvements. HUD also administers the Lead Hazard Control and Healthy Homes Program, which conducts research and provides grants to reduce home health hazards relating to lead-based paint, exposure to mold, moisture, poor indoor air quality, pesticides, dust, and other substances that contribute to poor health outcomes. The rise in prominence of green building since the 1990s has raised questions about its impacts. Those questions cover a broad range of issues, including market penetration, cost, actual building performance, the underlying measurement science, the extent to which legislative goals are being met, and the general approach and implementation of green building. Those issues are discussed below. The building industry is a substantial component of the U.S. economy. In 2016, the total value of construction and renovation work in the United States exceeded $1 trillion and accounted for more than 6% of U.S. gross domestic product (GDP). The percentage of the overall construction market devoted to green building has grown substantially in recent years, spurred by a variety of factors, from government requirements to the prospect of attractive investment returns to increasing concerns about environmental degradation and quality of life. In 2005, according to one analysis, only 2% of new residential and commercial construction in the United States consisted of green building. By 2013, that percentage was estimated to have grown to 20%. Green construction spending in the United States has been growing faster than general construction spending as a whole. Spending on green construction more than tripled from $39 billion in 2008 to $129 billion in 2014. One analysis projected that green building activities will generate $303.4 billion in GDP between 2015 and 2018. New institutional construction is expected to be a large future driver of green building growth in the United States, primarily due to certification requirements for public buildings and schools. The percentage of certified-green floorspace may also be on the rise among existing buildings, although estimates vary significantly. The National Green Building Adoption Index has reported a rise in the percentage of office space that has been certified by LEED or Energy Star from 5% in 2005 to 38% in 2016 for the 30 largest U.S. office markets. Nevertheless, there remains a large portion of the U.S. residential and commercial building stock that was not constructed according to green building criteria and for which rapid retrofitting or replacement to meet those criteria does not seem feasible. Green building efforts can impact the financial performance of a building by affecting initial construction costs, operating expenses, rental rates, and property values, among other factors. Actual and perceived costs of implementing green building measures have a strong bearing on design and construction decisions. However, information on true costs is not always easy to obtain, and such informational barriers can distort perceptions about the economic benefits of green building. Moreover, researchers have noted that the flexibility inherent in designing individual green buildings makes generalizing about the cost performance of the market segment as a whole difficult. As a result, empirical evidence of the financial performance of green building investments is limited. It is widely believed that the initial costs of green buildings are higher than for conventional buildings. A survey of construction industry professionals found that higher perceived initial cost was among the top three obstacles for green building in the United States. Such higher costs can result from several sources. Not only can many features, such as high-efficiency appliances and high-performance windows, be more expensive than conventional approaches, but design costs may be higher, and if the building is to be certified, the process may be time-consuming and expensive in its own right. There is some evidence, however, that the costs for constructing green buildings are not substantially higher than those of standard construction. A DOE review of the existing literature on green-certified buildings concluded that the available evidence shows construction costs for green buildings to be comparable to those of conventional buildings. The use of integrated design may also result in some reductions in initial costs, and some evidence supports that claim. Proponents of green building assert that operational cost savings will eventually recoup any initially higher investment. One way green buildings can create operational cost savings is by reducing usage of utility resources, and, in some cases, through selling site-generated renewable energy back to the grid. GSA, for instance, claims to have saved over $340 million in energy and water costs between FY2008 and FY2015 from efficiency improvements. More than two dozen studies support the contention that green certification is associated with reduced utility expenses. However, utility costs, such as electricity, gas, and water bills, only make up approximately 19% of a commercial building's operating costs, and evidence is mixed on whether green certification reduces overall operating expenses. There is also evidence to suggest that green-labeled buildings command price premiums on the real estate market, both in the amount that renters are willing to pay to use the space, and in terms of overall market value. Some features of real estate markets can, however, reduce incentives for investments in green building. For example, building owners, especially homeowners, often move after a few years, reducing the time they would require for a return on their initial investment through potential utility savings. The problem can be exacerbated if the building is rented or leased. The financial return on green building investments made by owners would depend on how much of a premium they could charge current or new tenants. The return for investments by tenants would depend on the length of their tenure—only long-term tenants would be likely to benefit from making such an investment. This is sometimes called the principal/agent or split-incentive problem. Finally, many potential beneficiaries of green building renovations may be limited by constraints on the availability of capital for such investments, even outside the residential sector. Such constraints are reported to be a problem with respect to such significant users of energy as educational institutions, hospitals, and municipalities. Cost barriers to the use of green building may continue to decrease as the practice becomes more widespread and economies of scale lower the initial cost differential. Also, financial incentives, offered by some states and municipalities, may help to defray higher initial costs, making green building investments more financially attractive. Some observers argue that costs beyond simple monetary expenditures should be considered. Such thinking has led to the use of concepts such as the "triple bottom line" in literature on green building. The term refers to the inclusion of social and environmental returns, in addition to financial ones, in assessing business performance. In evaluating the efficacy of green building efforts, it is necessary to distinguish between design and performance. Much of the focus of green building, including rating systems such as LEED, has been on design and construction specifications. Historically, actual environmental performance of green buildings was not incorporated into certification requirements for most rating systems. There are, however, many factors that can affect operations and potentially degrade the performance of a building after it has received its green rating. Such factors include inadequate maintenance of systems, alterations to prescribed building controls, and unintended changes in building use and occupancy. Consequently, it is not certain that a nominally green building, even one for which the design and construction are certified, will perform in a manner that is significantly better or worse than a conventional building. Indeed, there are well-publicized examples of certified green buildings that have been shown to be extremely resource-intensive postoccupancy. Studies that have evaluated actual green building performance are discussed later in this section. However, even where greater resource-use efficiency can be demonstrated, savings may be offset by other factors. For example, green building efforts and related energy-efficiency initiatives appear to have helped reduce energy-use intensity (see " Measurement ") in U.S. homes built since 2000. Yet, those homes use more total energy on average because they are 30% larger than older ones and have more electronic appliances and other devices. The energy performance of green buildings has received the most scrutiny. Researchers have shown that there is often a significant difference between the predicted or modelled energy use of a building and its measured performance. This difference is sometimes referred to as a "performance gap." Closing that gap is a topic of ongoing interest and concern to the construction industry. In response to such concerns, rating system developers have placed increasing emphasis on postoccupancy performance assessment. Recent revisions of the LEED rating system have sought to address critiques centered on the one-time assessment nature of certification by requiring installation of building-level energy and water meters, the data from which are to be compiled and reported to USGBC for the first five years following certification. Other systems, such as BREEAM In-Use and the Living Building Certification, explicitly include performance parameters within the criteria for certification (see " Green Rating Systems and Certifications "). Building codes are also moving toward incorporating performance outcomes into requirements: the 2015 IgCC included an outcome-based compliance pathway for energy usage, allowing builders to meet requirements through actual performance. Building systems may also be commissioned—that is, independently assessed to ensure they are designed, installed, tested, and capable of being operated as planned. Available data support the contention that commissioning improves environmental performance, especially for energy use. The process can be used not only for new buildings, but also existing ones, either during retrofitting or continuing operations. In addition to certification and commissioning, an organization can develop an environmental management system (EMS), for which international standards are available. To be certified under the standards, an organization must have an explicit environmental policy that includes commitments to conform to relevant environmental requirements, continuously improve environmental performance, and prevent pollution, among other things. Such commitments are arguably far easier to meet if the EMS includes performance measurement. Networked building monitoring and diagnostic tools are becoming increasingly prevalent. Such tools can allow early fault detection in critical building equipment as well as providing resource use analytics, allowing building managers to more effectively respond to changing use patterns in real time. (See textbox " Smart Buildings and the Internet of Things ," above.) For example, GSAlink, a GSA-developed building diagnostic tool, has been used to identify over 33,000 instances of sub-optimal equipment performance within GSA holdings alone. Many studies have attempted to measure and evaluate green building performance. However, a lack of consensus on the criteria for defining green building, as well as on the outcomes to be measured, has made it difficult to compare results between studies. Generally, the evidence that green buildings perform significantly better than conventional buildings is mixed. Recent studies have shown green buildings to exhibit a wide range of measured energy performance, with some buildings performing far below design expectations. The selected studies discussed below primarily use LEED ratings as the criteria for inclusion. Because other rating systems are not as prevalent in the United States, little information is available on the performance of buildings constructed under those systems in the U.S. market. A study of energy use by more than 100 LEED-certified buildings found that, on average, they performed 24% better than other buildings. However, about one in seven performed worse than average. This study was criticized as misleading because of purported sample bias, inappropriate baselines for comparison, and other concerns. A follow-up assessment using the same data concluded that primary energy savings from LEED certification were nonexistent for lower levels of certification and 13% better than average for Gold and Platinum-certified buildings. A GSA study of 22 green federal buildings, most of which had received LEED certification, found that, on average, the buildings studied performed better than the national average in all measured performance areas, including energy use, water use, operating costs, occupant satisfaction, and carbon emissions. Some buildings performed worse than the national average in certain areas, however. A study of the energy consumption of 11 LEED-certified Navy buildings found that 9 of the 11 buildings did not meet the federal requirement at the time of the study (30% electricity savings over the benchmark). Furthermore, the majority consumed more electricity than the national average. An assessment of Arizona's LEED-certified new construction buildings supported the existence of the energy performance gap, as the majority of the sample underperformed both the design and the baseline energy-use simulations, highlighting a disconnection between the efficacy of the strategies employed and the modeling results. Taken together, the findings in those studies do not appear to provide sufficient evidence of improvements in performance with LEED certification to conclude that such certification consistently reduces building energy consumption. However, sample sizes were small and may not be representative of the overall performance of green-certified buildings. Performance data is often proprietary and therefore often inaccessible to researchers conducting evaluations. Greater access to building performance data is frequently cited as a prerequisite to more comprehensive performance assessments. As the discussion above shows, performance measurement is important for ensuring that green buildings meet the environmental targets claimed for them and to assess ways to improve those targets. However, methods for measuring the performance of green buildings are not yet well-developed for most elements. Some, such as energy and water use, are comparatively easy to measure quantitatively, for example through metering. Others may be difficult to quantify and may be possible to evaluate only on the basis of the presence or absence of certain features or through other more qualitative measures. Even for elements that are relatively simple to measure, such as energy usage, there may be disagreement about which of several possible metrics captures the most relevant information. For instance, energy use intensity (EUI), which is the primary metric used to evaluate federal building performance, has traditionally been defined as the amount of energy used per square foot. GSA's Green Building Advisory Committee has recently proposed two additional methodologies for measuring EUI: energy use per occupant and area-based EUI measuring energy used in commuter transportation to and from the building. As the Advisory Committee notes in its report, a building's energy use patterns may appear to vary based on which metric is used. However, a study by Pacific Northwest National Laboratory cautioned that a lack of accurate building occupancy data could complicate efforts to calculate occupancy-adjusted EUI. Furthermore, there is some evidence that commonly accepted metrics, such as an Energy Star score, are not highly correlated with the outcomes they are intended to measure. Given the life expectancy of buildings—in most cases far longer than occupancy by any given resident—measurement of performance is important not only initially but over the building's entire lifespan. In the absence of such regular measurement and adjustment, environmental performance is likely to deteriorate over time for many elements. Eventually, some form of standard life-cycle assessment may be feasible for whole buildings. EISA requires that federal agencies measure the performance of their buildings against specified targets, especially with respect to energy use. Targets are more stringent for new construction than existing stock. Energy performance is to be measured against a baseline of consumption levels in 2005. Determination of an accurate baseline may be difficult in the absence of adequate measurement of energy use. Despite the recognized importance of measurement and the availability of options and resources for its application, uncertainties and gaps exist that can make effective application challenging. Consensus may not exist on specific measurement goals or metrics. Reliable and consistent data are often difficult to obtain. Measurement science relating to green building is an active area of research. In 2008, the National Science and Technology Council listed the development of appropriate measurement science as the top research need for progress in green building. Developing metrics and tools for measuring building sustainability is a priority of the National Institute of Standards and Technology. Agency progress toward meeting federally mandated green building goals varies widely. In the Obama Administration, OMB released annual sustainability and energy scorecards for each agency with sustainability reporting requirements. Scorecards reported on agency progress toward federal sustainability goals in the following areas: Scope 1 and 2 GHG Emission Reductions, Scope 3 GHG Emission Reductions, Reduction in Energy Intensity, Use of Renewable Energy, Reduction in Potable Water Intensity, Reduction in Fleet Petroleum Use, and Green Buildings. Scorecards included both numeric reports of agency progress, in the form of percentage reductions in target areas, as well as a color score of green, yellow, or red. The precise meaning of a score color differed slightly for each target area. Generally, however, a green score indicated that an agency had met or was on track to meet the target; yellow indicated that some progress has been made toward a target; and red indicated that the agency was neither on track to achieving a given target nor demonstrating significant progress. Federal progress toward three buildings-related goals is discussed below. See Table 2 for information on the reported progress of selected agencies toward those goals. Green Building Goal: E.O. 13693 directed federal agencies to ensure that at least 15% of agency buildings with more than 5,000 square feet of floorspace comply with the Guiding Principles by FY2025. Some agencies have already surpassed this target, while others are making progress. At least three agencies have achieved compliance in fewer than 2% of buildings, however. Several more have received a red score in the green buildings category from OMB for FY2015. Energy Intensity Goal: EISA set a goal for federal facilities to reduce energy intensity by 30% from 2003 levels by 2015. Many agencies did not meet this goal. Government-wide energy intensity declined only 22% during this period. E.O. 13693 directs agencies for reduce energy intensity by 2.5% per year relative to 2015. Progress on this goal will be reported starting for FY2016. Potable Water Intensity Goal: E.O. 13514 set a goal for a 26% reduction in potable water intensity between 2007 and 2020. E.O. 13693 replaced that goal in 2015 with a 36% reduction from 2007 levels by 2025. OMB scorecards for 2015 scored agencies on the basis of their progress toward achieving the earlier goal from E.O. 13514. Many agencies have already achieved the earlier goal, with several making substantive progress toward the 36% reduction required for 2025. Although green building is widely considered a positive development, some observers have expressed concerns about the approach. Some of those criticisms have been directed at rating and certification systems, for the reasons described above and others. The certification process is more rigorous for some systems than for others, and critics have pointed out that many systems do not set caps on performance metrics such as energy use, making claims to sustainability relative. Some argue that the design criteria are not sufficiently integrative—they do not provide sufficient integration across elements or stages in the building's life cycle—or that they are too incremental in scope. Others have argued that mere mitigation of environmental impacts is not sustainable, and that new approaches are preferable, for example based on maintenance or even enhancement of ecosystem services. Such approaches would arguably need to go beyond individual buildings and include other components of the built environment. Some observers worry that builders new to green building may fail to appreciate the importance of taking a forward-thinking, integrative approach to green building design. Instead, some may regard green building measures as items that can simply be tacked on to a construction project, rather than being an integral part of the project from its inception onward. The scientific and technological knowledge base for green building is also limited, which is not surprising given the recent origin of the discipline. These limitations make it difficult to identify the most appropriate approaches. Substantial research is considered by many as needed to improve the knowledge base relating to all elements of green building. Such issues can be compounded by differences in goals and perspectives among different proponents of green building. Identifying objective, rather than subjective, criteria and approaches may also be difficult, especially for elements of green building, such as siting, that are not as amenable to quantitative evaluation as others, such as energy. Four of the questions Congress may expect to face with respect to green building are How well are current federal green building programs working? How effective are current methods for coordinating the green building activities of different agencies? To what extent and by what means should Congress extend federal efforts to facilitate and support adoption and implementation of green building measures throughout the United States? What priorities should Congress give to the different elements of green building, especially those such as siting that have received less attention in the past? What actions should Congress take to facilitate the growth of scientific and technical knowledge relating to green building? If Congress wishes to take additional action on such questions, it could do so through appropriations, new statutory requirements, and tax law. It could also review current and proposed agency programs, regulations, and policies. GAO has released several reports over the last decade addressing various federal efforts relating to green building. One of those reports identified 94 initiatives across 11 agencies relating to green building in the nonfederal sector. However, few of those initiatives focused on green building in the integrative sense it is discussed in this report, but rather focused on specific elements such as energy, IEQ, or water. GAO recommended that agencies coordinate to assess the relative performance of the initiatives. Congress may wish to examine how well—in terms of both performance and efficiency—federal agencies are implementing green building programs, and what impacts those efforts are having on the adoption of green building practices both within the federal government and nationwide. In addition to oversight of the activities of individual agencies, it may also be useful to examine how well agency efforts are being coordinated. In addition to programs and activities such as those described above, some federal agencies such as the Federal Housing Administration and the Department of Veterans Affairs also support the availability of mortgages that promote energy efficiency. Lenders who provide such mortgages may also become Energy Star partners. If Congress finds that such measures are not adequate, it could consider such steps as providing stronger mortgage and tax incentives, broadening the scope of mortgage and tax incentives to include elements of green building in addition to energy, funding the rebate program authorized by EPACT 2005, and specific appropriations to speed adoption of green building in areas where market penetration has been lagging, such as residential renovation. Congress could also consider regulatory actions, although such efforts might be complicated by federalism issues and differences in regional requirements relating to climate and other variables. Congress could consider identifying ways in which current green building efforts in federal agencies could be further enhanced. In addition to accelerating green building for new and existing stock, Congress might consider whether programs and activities are sufficiently integrated within agencies such as EPA and DOE, and whether activities across agencies are sufficiently harmonized, such as through participation in the WBDG (see the text box " Whole Building Design Guide ," above). Among the elements of green building discussed in this report, energy has received far more attention than any other. This priority is not surprising, given concerns about fossil fuel imports, strategic vulnerability, negative effects of climate change, and the high and inefficient levels of use of energy by most of the current building stock in the United States. Nevertheless, Congress may wish to examine whether federal efforts in green building are effectively balanced among the component elements. If they are not, existing programs relating to particular elements could be strengthened or new ones established. In addition, Congress may wish to explore whether the incremental approach embodied in most green building activities is sufficient to address national needs, or if some modification or acceleration of efforts would be preferable. Development of the scientific and technological knowledge base for green building is supported by R&D funded by both federal and private-sector sources. Levels of funding from both sources may be suboptimal to address the needs currently identified. According to a 2007 study, green building received less than 0.5% of total funding for federal nondefense R&D. Also, a 2003 study found that despite its economic importance, construction sector investment in R&D was at a much lower rate than the industry average. Funding for R&D relating to the different elements of green building has also varied, with some elements such as energy being a much higher priority than others. That may well be considered appropriate by most observers, but given the range of green building elements and the need for improved knowledge about them, as well as the accepted importance of integration and economics to successful green building efforts, Congress may wish to consider whether federal funding levels and priorities should be modified, and whether to create incentives for increasing private-sector R&D funding. In addition, Congress may wish to consider whether the availability of training and education relating to relevant areas of expertise is sufficient to ensure a knowledgeable workforce for construction, certification, and operation of both federal green buildings and others, such as schools and hospitals (see the textbox " Special-Use Buildings ," above). 

Summary: Buildings, whether residential, commercial, government, or special-use, are core components of the nation's infrastructure. Their construction, operation, and demolition are increasingly recognized as major sources of environmental impact. Without significant transformation of building construction and operations, that impact is expected to increase with population growth and changes in other demographic and economic factors. One strategy for achieving that transformation is most widely known by the term green building. However, the term is used differently by various proponents and practitioners, denoting a continuum of practices, from those differing minimally from standard practices, to those aimed at providing buildings with a minimum of environmental impact. In general, green building can be characterized as integrated building practices that significantly reduce the environmental footprint of a building in comparison to standard practices. Descriptions of green building generally focus on a number of common elements, especially siting, energy, water, materials, waste, and health. Serviceability or utility is also an explicit design element for a class of green buildings known as high-performance buildings. One of the most salient features of green building is integration of the various elements. Although individual elements can be addressed separately, the green building approach is more comprehensive, focusing on the environmental footprint of a building over its life cycle, from initial design and construction to operations during the building's useful life, through eventual demolition and its aftermath. The desire to integrate the various elements of green building has led to the development of rating and certification systems to assess how well a building project meets a specified set of green criteria. The best-known system is Leadership in Energy and Environmental Design (LEED). Developed by the U.S. Green Building Council, it focuses on site, water, energy, materials, and indoor environment. Recently, green building practices have found their way into building model codes and technical standards. Green building has received substantial attention from government, industry, and public interest groups. Several federal laws and executive orders have provisions relating to green building. Among these are the energy policy acts (EPACTs) of 1992 and 2005 (P.L. 102-486 and P.L. 109-58), the Energy Independence and Security Act of 2007 (EISA, P.L. 110-140), and Executive Order 13693. EISA and other policy instruments require all federal agencies to implement green building practices. However, several agencies have programs and activities that have a focus that goes beyond reducing the environmental impacts of the facilities used by that agency—for example, by performing research or facilitating the green-building activities of nonfederal entities. Among those agencies are the General Services Administration, the Environmental Protection Agency, the Office of Federal Sustainability, the National Institute of Standards and Technology, and the Departments of Defense, Energy, and Housing and Urban Development. Green building raises issues relating to performance, cost, market penetration, and the approach itself. Among the questions Congress may face with respect to such issues are the following: How well are current green building programs working? How effective are current methods for coordinating the green building activities of different agencies? To what extent and by what means should Congress extend its efforts to facilitate and support the adoption and effective implementation of green building measures? What priorities should Congress give to the different elements of green building? What actions should Congress do to facilitate the growth of the scientific and technical knowledge base relating to green building?