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Weekly UpdatesA MAJOR ISSUE IS EVOLVING WITH REGARD TO THE MEANING and implications of the term "building performance." To some, this expression means a promise to design buildings that will function in accordance with "green" or "high-performance-green" ratings. Others aspire to operate safe, secure and healthy buildings. And most owners expect their buildings to yield attractive rates of return on investment. Yet the criteria with which to measure and evaluate actual building performance are seldom defined in objective and measurable terms. The intent of this article is to explore this issue by reviewing the concepts and principles of building performance, the functional status of the existing building stock, and the risks and opportunities associated with accountability for the performance of these buildings.
THE IMPORTANCE OF BUILDING PERFORMANCE
Fundamentally, buildings have a two-fold purpose: 1) to provide safe, healthy and secure conditions for occupants; and 2) to facilitate the well-being and productivity of the occupants, owners and managers of the property. If buildings are designed, constructed and operated for this purpose, the natural consequences are effective use of energy, environmental and financial resources. Conversely, if promises and policies are made to minimize energy consumption and environmental impact without achieving the two-fold purpose, then safety, health, security, and economic risks are likely to increase.
To credibly account for how well a building is achieving its two-fold purpose at any time during its useful life, objective methods for measuring and evaluating building performance are required. Based on principles of control theory and the assumption that a building functions as a system:
Building performance can be defined as a set of measured responses of the building, as a system, to anticipated and actual forcing functions. (1)
In this definition:
* Measured responses are data that are obtained in terms of valid parameters and values of human responses (e.g., perceptions and judgments), occupant exposures (e.g., environmental stressors that affect human responses), system performance (e.g., measurable factors that affect occupant exposures), energy consumption and economic performance (e.g., consequences of system performance and occupant behavior). (2)
* Forcing functions are quantitatively determined physical and social forces that perturb the building system and the measured responses during both normal and extraordinary conditions. (3) Sources of physical forces include climate (outdoor temperature and humidity conditions), wind, rain and snow loads (hurricanes, tornados, blizzards), earthquakes, fires, floods, chemical and biological releases, and blasts. Sources of social forces include aesthetics, economic and other motivations of occupants, tenants and owners, secular trends (e.g., policies on smoking, green practices), and threats (e.g., job security, reliability of utilities, criminal intent, terrorist activities).
This definition of building performance does not presume a predetermined quality of performance. However, some other definitions have been promulgated that promise a certain quality of performance (e.g., green, high, net-zero energy, sustainable), but have not defined the constellation of forcing functions or the set of responses in measurable terms that can be used to evaluate and account for the actual building performance under normal or extraordinary conditions, which may be caused by natural, accidental or intentional hazards. (4) Such a qualitative definition has recently been proposed by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE): (5)
A high-performance green building is defined as "a building designed, constructed and capable of being operated in a manner which increases environmental performance and economic value over time, safeguards the health of occupants, and enhances satisfaction and productivity of workers through integration of environmentally-preferred building materials, and water-efficient and energy-efficient systems." (Emphasis added)
In this ASHRAE definition, the physical or social forcing functions for normal and extraordinary conditions (e.g., weather conditions and anticipated hazards) are not identified, but the italicized terms promise improvements (i.e., increases, safeguards, enhancements) of response functions and processes that may not be quantitatively measurable.
A comparison of these definitions indicates that risks are inherent in promising building performance that cannot be objectively measured and evaluated for compliance with established criteria (e.g., building codes and standards, contract requirements, owner and tenant policies). Some of the risks associated with the unfulfilled promises of achieving high-performance green buildings during the design process have been discussed by Butters. (6) Similar risks are also expected as a result of unfulfilled promises made to justify modifications, renovations, or changes in operations within existing buildings.
FUNDAMENTAL CONCEPTS AND PRINCIPLES OF ENVIRONMENTAL CONTROL
To achieve and sustain the fundamental purpose of buildings, environmental control must be provided to meet the following objectives:
(1.) Prevent adverse health and safety effects during normal and extraordinary or emergency operational conditions; (7)
(2.) Provide for desired conditions of human response, occupant exposure, and productivity. (8)
In general, the quality of control required to achieve the second objective also provides the means and methods required to achieve the first objective.
TWO PRIMARY PRINCIPLES
To meet these objectives, simultaneous control is required for at least four indoor environmental parameters (i.e., thermal, lighting, acoustics and indoor air quality [IAQ]). The priority of the site-specific control strategies and the range of values of the selected control parameters should be based on two primary principles: 1) the Maslow Hierarchy of Needs (physiological, safety and security, belonging, esteem and self-actualization); (9) and 2) the definition of Health as defined in the Constitution of the World Health Organization (WHO): "A state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity." (10) From the perspective of building design and operations, these two principles are synergistic:
* The WHO definition of Health emphasizes that control to prevent illness is necessary but is not sufficient to provide for occupant well-being;
* The Maslow Hierarchy of Needs emphasizes that control to provide for occupant well-being must include the higher order needs of belonging, esteem and self-actualization.
SUSTAINABLE DESIGN
As shown in Table 1, a set of three objectives and six principles has now been incorporated into another concept of building performance: "sustainable design."
These objectives and principles, which promise both outdoor and indoor environmental control, are similar to ASHRAE's definition of high-performance green buildings. They promise a certain quality of performance through design without defining the constellation of forcing functions or a set of responses in measurable terms that can be used to evaluate the actual building performance under normal or extraordinary conditions. Moreover, these objectives and principles appear to invert the control priority established by the Maslow Hierarchy of Needs and to exacerbate the risks in promising sustainable building performance. As typically advocated, these objectives and principles tend to focus first on minimizing the impact of building performance on climate change and depletion of natural resources, then on controlling for the health, safety and well-being of the building occupants. Taken to its logical extreme, this apparent inversion would require that buildings not be built or operated. Conversely, if buildings are to function, they must provide for occupant health, safety and well-being; and the physical laws of nature require the use of energy, other natural and human resources, and the necessary discharge of waste products. Therefore, integration of the objectives and principles of sustainable design should focus primarily on developing and using quantitative measures to assure compliance with the Maslow Hierarchy of Needs.
RISK MANAGEMENT
A critically important lesson has been learned during the last two decades. Buildings must be resilient: they must perform under normal forcing functions during their entire useful lives, and be prepared to effectively respond during and after the occurrence of extraordinary forcing functions caused by relatively short periods of natural disasters, accidental incidents and intentional events. (12)
The strategies for resilient control during the normal and extraordinary periods should be evaluated and updated through periodic risk assessments of the specific site, which identify the threats (i.e., forcing functions), the vulnerabilities or weaknesses in the building system (i.e., measured responses), and risks that can result. As an example of resilient control, consider the required performance of a building with a critical need to continue its operations during an extraordinary weather event. It must have adequate emergency and redundant electrical power generating equipment (e.g., diesel generators), HVAC capacity, and flexibility of control to provide for occupant health and safety; and it must reliably power the critical operations during the event in addition to re-establishing normal operations rapidly after the event. A flow diagram of this resiliency is shown in Figure 1.
[FIGURE 1 OMITTED]
A building is subject to vulnerabilities under normal as well as under extraordinary conditions which may be markedly different. An energy efficient system during normal conditions may prove to have very high vulnerabilities to intentional acts or vice versa. No building can avoid a level of residual risk which remains no matter what the desire to eliminate all risk. Rather, this residual risk needs to be managed. In fact, the resiliency of a building is its capacity to minimize this residual risk so that it can quickly return to its proper functional reason for being.
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