James E. Woods, Ph.D., P.E.

Article One of Four

INTRODUCTION
As accountability increases for performance of buildings and their systems, the need increases for valid and reliable testing, adjusting and balancing (TAB) of HVAC and whole building systems. Building owners and managers, designers, manufacturers and contractors have realized for many years that these systems reduce energy and operating costs when they perform as intended by design. However, within the last few years, and especially within the last year, a renewed awareness has also been realized that the performances of these systems affect occupant health, safety, sense of well-being and security, and productivity. Through the establishment of the Testing, Adjusting and Balancing Bureau (TABB), a certification program now exists that synchronizes performance evaluation of all components in an HVAC system in order to assist building owners and designers in gaining assurance that the HVAC and whole building systems are performing in accordance with the design specifications.

This series of articles will explore the technical aspects of TABB Procedures that can be used to assure HVAC and whole building performance during normal and extraordinary (i.e., naturally occurring, accidental, or intentional) conditions. This first article focuses on the needs and foundations for the current TABB Procedures. In the second article, current and future procedures for diagnosing and commissioning building performance will be explored. The third article will focus on procedures needed to assure acceptable human responses, occupant performance, and productivity. And the fourth article will consider procedures needed to ascertain desired HVAC and whole building performance during normal, and to ascertain the "preparedness" of these systems to effectively respond to extraordinary (i.e., naturally occurring, accidental, or intentional) conditions. The intent of this series of articles is to stimulate discussion regarding the challenges and opportunities associated with accountability for the performance of HVAC and whole building systems, including the provision of credible documentation.

NEEDS AND FOUNDATIONS FOR TABB PROCEDURES
A fundamental need in assuring HVAC and whole building system performance is the "Continuous Accountability" that must exist during the planning and design, construction, and operational phases of a building. If design documentation is not complete, or the owner and designer have not adequately expressed the intended performance of the HVAC or building systems, the results from any TAB procedures, no matter how well conducted, cannot assure occupant health, safety, or environmental security. Nor can TAB results, alone, assure energy efficient or cost-effective building performance and productivity during normal conditions, or "preparedness" of HVAC or building systems for responses to extraordinary conditions. Conversely, if the design intent is clearly expressed but TAB results are not credible, assurance cannot be obtained that the HVAC or whole building systems are performing as intended to provide for the needs of the occupants or the building owner. Therefore, credible TAB results are necessary but not sufficient to assure HVAC or whole building performance.

The objective of this article is to express the conceptual and technical framework underlying the credibility of the TABB Procedures. In the first part of this article, the concepts of Continuous Degradation, Continuous Accountability, and Building Diagnostics are introduced. In the second part, the importance of psychrometrics to assuring system balances is emphasized. And in the third part, the current and future needs for "Testing, Adjusting and Balancing" are discussed.

CONCEPTUAL FRAMEWORK
The primary purpose of buildings is to provide secure, safe, and healthy conditions for the occupants. The secondary purpose is to facilitate the well-being and productivity of the occupants, tenants, and building owners. In this article, buildings are categorized as Residential, Commercial and Public Assembly, Educational, and Health Care. While each of these categories may require some differences in TABB Procedures, each also has two fundamental objectives of environmental control: 1) to prevent adverse health or safety effects, and 2) to provide for the desired conditions of human response, occupant performance, and productivity.

CONTINUOUS DEGRADATION
According to the U.S. Department of Energy, approximately 4.7 million commercial (e.g., office and public assembly, educational, health care) buildings and 100 million residential buildings exist in the U.S. These are being replaced at a rate of approximately 1 - 2 % per year. Therefore 80 - 90% of the buildings that will exist twenty years from now have already been built. These facts lead to the logical conclusion that the performance of existing buildings, as well as new buildings, is critical to the health, security and productivity of the country. However, all of these buildings are not currently performing as intended. As reported by this researcher and others, approximately 50 - 70% of the existing building stock perform as intended (i.e., "Healthy Buildings") and 10 - 20% perform with "Undetected Problems," but 20 - 30% have significant problems characterized as "Sick Building Syndrome" (i.e., 10 - 25%) or "Building Related Illness" (i.e., 5 - 10%). This characterization of the performance of the existing building stock has been described as "Continuous Degradation."

CONTINUOUS ACCOUNTABILITY: A Professional Role for TABB
Interception and recovery from this Continuous Degradation process requires knowledge and commitment. As shown in Fig. 1, the knowledge is obtained from diagnosing the cause of the degradation. From the results of the Building Diagnostics, interventions can be identified and implemented to regain the Healthy Building performance. This process of assuring the Healthy Building status has been described as "Continuous Accountability."

Fig. 1 Intervention of Continuous Degradation

To achieve Continuous Accountability, three commitments are required. First, an Accountable Person must be identified for each phase of the building's life (i.e., planning, design, construction, and operations). Second, the Accountable Person at each phase must be empowered with the authority to assure the required performance during that phase. Third, the Accountable Person at each phase must possess the education and training to assure the required building performance and protection of the occupants. TABB's Mission Statement is consistent with this concept of Continuous Accountability:

"The Testing, Adjusting and Balancing Bureau (TABB) is committed to the welfare of the general public, engineers, building owners and design professionals to assure that all building environmental systems are installed properly and all systems are adjusted to these design specifications. TABB Certified Professionals subscribe to a strict Code of Conduct and pledge to regularly upgrade their skill level to meet cutting-edge technological advances in the heating, ventilation and air conditioning industry."

During the design phase, the TABB-Certified Professional (i.e., TABB-Certified Supervisors and Contractors) can assist the Accountable Person (e.g., owner or designer) in specifying and documenting the performance requirements of the systems, including the Commissioning Process, Value Engineering, and the Substantial Completion Process. During the construction phase, the TABB-Certified Professional may take a leadership role in Commissioning, Value Engineering, and TAB processes to assure that the installed systems are performing in accordance with the design intent (i.e., in compliance with design documentation and evaluation criteria). During the operations phase, the TABB-Certified Professional can assist the Accountable Person (e.g., building owner) in assuring that the systems continue to perform in accordance with design intent.

BUILDING DIAGNOSTICS: A Technical Role for TABB
A fundamental tool required in Continuous Accountability is Building Diagnostics, which has been defined by the National Research Council as a "Process in which a skilled expert draws on available knowledge, techniques and instrumentation in order to predict a building's likely performance over time." Four essential elements are required in Building Diagnostics: 1) knowledge of what to measure; 2) availability of appropriate instrumentation; 3) expertise in interpreting the measurements; and 4) capability of predicting likely performance. Therefore, Building Diagnostics is a hypothesis-based process that is intended to detect a true outcome with a minimum of false positive or false negative errors. During the design and construction phases, the Building Commissioning process may be considered as a subset of the Building Diagnostics, but it is not hypothesis-based and does not minimize the occurrence of false positive or false negative errors. The differences between Building Diagnostics and Commissioning processes will be further discussed in article two.

During the design and construction phases, TABB-Certified Professionals and Technicians can assist the Accountable Persons (e.g., owner, designer, contractor) by supporting or leading the Commissioning and TAB processes. During the operations phase, the TABB-Certified Professionals and Technicians can assist the Accountable Person (e.g., building owner) by supporting or leading the Building Diagnostics procedures for investigations regarding complaints, opportunities for improved productivity, or assurance of preparedness for environmental security.

PSYCHOMETRICS AND SYSTEM BALANCES: A Technical Foundation for TABB
The two fundamental objectives of environmental control are achieved through the simultaneous control of thermal, indoor air quality, lighting, and acoustic parameters. To assure this simultaneous control, energy and mass balances for the occupied spaces, as well as for the HVAC and whole building systems, are needed. Three basic mechanisms for energy and mass transfer exist with which to control these parameters within predetermined sets of values (i.e., control criteria): conduction, radiation and convection. Conduction is important for heat, and sound and vibration transfer across building materials; radiation for sensible heat, lighting and sound transfer between occupants and their enclosed spaces; and convection for heat, contaminant, and sound transmission within and across occupied spaces. Of these, convection is unique as it is an effective means of sensible heat transfer and the only means of controlling the mass transfer of gaseous and particulate contaminants, moisture, and water vapor and its corresponding latent heat transfer. Therefore, to provide assurance that the two fundamental objectives of environmental control are being achieved in new or existing buildings, credible documentation is needed for the air distribution performance within occupied spaces; through supply, return, and exhaust air plenums and ductwork; and at local and central control devices for heat and mass exchange.

Although the principles of psychrometrics do not extend to applications for performance analysis (e.g., energy balances) of lighting and acoustic systems, these principles are critically important to assuring the performance (e.g., energy and mass balances) of the thermal and air quality control systems. Psychrometrics literally means the "measurement of cold" and is practically defined by ASHRAE as "determining the thermodynamic properties of moist air, and using these properties to analyze conditions and processes involving moist air." Therefore, air quality control is a natural extension of psychrometrics and focuses on the interactions between moist air and airborne contaminants.

Psychrometric analysis conventionally involves the simultaneous solutions of steady-state, energy and mass balance equations in the form of Q = ma Dh and W = ma Dw. In these equations, Q is the heat transfer rate (Btu/hr), W is the transfer rate of water vapor (lb water vapor/hr), ma is the mass air flow rate (lb dry air/hr), Dh is the enthalpy difference (Btu/lb dry air) across the controlled device (e.g., cooling coil, occupied space, etc.), and Dw is the difference in humidity ratio (lb water vapor/lb dry air) across the controlled device. Extension of the psychrometric principles to analyze air quality control systems only requires the conversion of the mass balance equation for water vapor to other contaminants: X = ma Dx. In this case X replaces W and represents the transfer rate of any air contaminant such as water vapor, CO2 or particulate matter (mg contaminant/hr), ma is the mass air flow rate in consistent dimensions (kg dry air/hr), and x is the concentration of the contaminant (mg contaminant/kg dry air).

Until tabulated data on emission rates of contaminants become more readily available, a practical approach to psychrometric analysis of air quality control systems may be taken in two steps: 1) conduct conventional psychrometric analysis for moist air, but pay particular attention to humidification/dehumidification control; 2) verify that the system selected in step one complies with the required contaminant balances for the specific contaminants of concern and modify the selection as necessary. Step two can usually be performed with analytical tools such as spreadsheets. TABB-Certified Professionals and Technicians can assist the Accountable Persons (e.g., owner, designer, contractor) by obtaining the appropriate field data and by providing leadership in this two-step analytical process.

CURRENT AND FUTURE NEEDS FOR "TEST, ADJUST AND BALANCE"
The three terms "Test, Adjust, and Balance" are often taken for granted in our industry. However, in terms of Continuous Accountability, each of these terms takes on additional meaning: Test for what? Adjust to what criteria? Balance what?

Currently, "Testing" conventionally means obtaining and reporting data on air-side and water/refrigerant-side pressures and flow rates of controlled devices, temperature and moisture content of the air in these systems and in the occupied spaces, and some sound pressure and electrical power data associated with components in the HVAC systems. Within the near future, it is likely that TABB Certified Professionals and Technicians will be requested by Accountable Persons to obtain and report on additional data needed to assure HVAC and whole building system performance.

"Adjusting" conventionally means calibrating or setting the controls of HVAC systems to some pre-determined criteria. During the TAB process, these criteria are usually assumed to mean "as specified in the design documents." However, when these criteria are not specified or not evident, "Adjusting" of the system becomes somewhat of an artform that is expected of the TAB contractor. As the concept of Continuous Accountability evolves, the criteria to which the systems are to be adjusted should become more objective.

Similarly, the meaning of the term "Balancing" is expected to become more explicit as the concept of Continuous Accountability increases. Today, the term typically means to rationalize the adjusted test values with the design criteria. Unfortunately, the results of the current process do not assure psychrometric balances at full or partial loads. Within the near future, however, it is likely that TABB Certified Professionals and Technicians will be requested by Accountable Persons to assure the energy and mass balances of HVAC and whole building systems needed to achieve performance in compliance with the specified criteria for acceptable human responses, indoor exposures (including thermal, air quality, lighting and acoustics), energy and economic performance, productivity, safety, and environmental security.

A question that arises from this discussion is what are the future roles and opportunities for TABB-Certified Professionals and Technicians? In the following three articles, this question will be considered regarding Building Diagnostics and Commissioning processes and methods to assure acceptable human response, occupant performance, productivity, and environmental security.