Commissioning of Existing Buildings - CiteSeerX

Commissioning of Existing Buildings – State of the Technology and It’s Implementation David E. Claridge, Texas A&M University Mingsheng Liu, University of Nebraska W.D. Turner, Texas A&M University

Abstract This paper provides an overview of the motivation and processes for commissioning new and existing buildings, with an emphasis on the processes for existing buildings. It also provides summary information on the results of commissioning existing buildings in the United States and shows the need for continuing follow-up. It concludes with a brief summary of the uses and ownership of about 20 million ft2 of existing buildings that have been reported in the literature to have been commissioned and estimates that 100 to 200 million ft2 of existing buildings have undergone some form of commissioning subsequent to initial occupancy. Introduction to Commissioning The energy crisis of the early 1970s spurred U.S. realization that buildings could be made much more efficient without sacrificing comfort. Over the last 30 years, the building industry has made revolutionary changes: chiller systems have decreased their power requirements by a factor of two, from over one kW/ton to less than 0.5 kW/ton; use of the variable air volume system has become common practice; and the use of building automation systems has become the norm with digital controls increasingly replacing pneumatics. These HVAC technology advances have greatly improved building comfort and have significantly decreased building energy consumption. The technological advances have increased the importance of proper operational practices in achieving the efficiency potential of the HVAC systems. Commissioning of HVAC systems has been growing in popularity over the last decade, but is still not the norm in construction practice or building operation. So many people have offered definitions of commissioning that one of the recommendations in the “National Strategy for Building Commissioning” (PECI, 1999) was “to develop a standard definition of commissioning.” The definition in ASHRAE Guideline 1-1996 (ASHRAE, 1996, p. 23) is probably closest to a standard or consensus definition: “Commissioning is the process of ensuring systems are designed, installed, functionally tested, and operated in conformance with the design intent. Commissioning begins with planning and includes design, construction, start-up, acceptance, and training and can be applied throughout the life of the building. Furthermore, the commissioning process encompasses and coordinates

the traditionally separate functions of systems documentation, equipment start-up, control system calibration, testing and balancing, and performance testing.” It is important to note that commissioning is a process, not a formula, or a body of technical knowledge. Consequently, the process, the stakeholders who participate in the process, the benefits of the process, and approaches for overcoming the disincentives that have limited use of commissioning must be emphasized; not a set of engineering formulas. However, commissioning relies on the broad body of technical HVAC knowledge, just as does the HVAC design process. In principle, all building systems should be designed, installed, documented, tested, and building staff trained in their use. In practice, competitive pressures and fee structures, and financial pressures to occupy new buildings as quickly as possible generally result in buildings which are handed over to the owners with minimal contact between designers and operators, minimal functional testing of systems, documentation that largely consists of manufacturers system component manuals, and little or no training for operators. This in turn has lead to numerous “horror stories” such as mold growth in walls of new buildings, rooms which never cool properly, air quality problems, etc. Such experiences were doubtless the motivation for the facility manager for a large university medical center who stated a few years ago that he didn’t want to get any new buildings. He only wanted to get three-year old buildings where the problems had already been fixed. The principal motivation for commissioning HVAC systems is to really achieve HVAC systems that work properly to provide comfort to all the occupants of a building unobtrusively and at low cost. They should work as soon as the building is occupied, and continue to work throughout the building’s life. It has been estimated that a properly commissioned new building which operates according to design intent will save 8% in energy cost alone compared with the average building that is not commissioned (PECI, 1999). This offers a payback for the cost of commissioning in just over four years from the energy savings alone and also provides improved comfort and air quality. The motivation for commissioning existing buildings is similar. Deferred maintenance and changes in building uses and functions typically lead to problems that are not fully resolved by the operating staff. Efficiency is further compromised, and PECI estimated

that commissioning the typical existing building would result in energy savings of 12%, with a payback of just over one year. So why are a growing, but still tiny fraction of new buildings commissioned each year and a miniscule fraction of existing buildings? Three main factors have been identified: - lack of awareness of the commissioning process and its benefits on the part of building owners and other industry professionals; - a perception that commissioning drives up initial cost and slows the construction process; and - insufficient data on the costs and benefits of commissioning (PECI, 1999). Commissioning is a term and process that was originally used by the navy to ensure that battleships and submarines functioned properly before they were sent out to sea. It has been adopted and adapted within the building construction industry to apply to many different levels. Total building commissioning refers to the commissioning of all systems and components within a building, to include the envelope, life safety systems, lighting systems, etc. as well as the HVAC systems. This paper will be restricted to the HVAC systems in buildings. Initial HVAC system commissioning efforts were restricted to new buildings, but it later became evident that while initial start-up problems were not an issue in older buildings, most of the other problems which commissioning tackled were even more prevalent in older systems. Finding budgets to fund the work and making the case for the services was initially difficult, but the economics for commissioning existing HVAC systems today are even more compelling than for new buildings Most buildings continuously evolve in terms of use and function. Hence, the HVAC systems tend to become outdated over time. Consequently, while commissioning an existing HVAC system to the design intent generally improves comfort and efficiency significantly, it is still likely to result in a sub-optimal system set-up. Continuous commissioning addresses these problems by explicitly considering current functions and uses of the building and requirements on its systems and attempts to optimize the efficiency of the systems for the current application, to the point that design intent is not addressed. Application of this approach to commissioning of existing HVAC systems has been found to typically result in 20% reductions in building energy use, with typical paybacks of one to three years (Claridge et al., 1998). Another important element in this approach is periodic examination of energy performance with follow-up as needed to maintain systems in a continuously commissioned state (Claridge et al. 2002). While some owners have adopted commissioning primarily because they find that it provides higher quality buildings and results in fewer initial and subsequent operational problems, the direct and rapid payback of the

commissioning expense from lowered operating costs is the principal motivation for many owners. Documenting these lower operational costs is much easier if a specific plan is implemented to monitor and verify the results of the commissioning process. Commissioning New HVAC Systems The goal of the commissioning process for a new HVAC system is to achieve a properly operating system that provides comfort to the occupants in every room from the first day a building is occupied. The motivation for commissioning a building is sometimes the desire to achieve this state as quickly, painlessly and inexpensively as possible. In other cases, the primary motivation is to achieve operating savings and secondarily to minimize operating problems, while motivations are more complex in some cases. Disney Development Corporation has constructed over $10 billion in new facilities since 1990 and has concluded that commissioning is an essential element for their company. The corporation often uses innovative construction techniques and creative designs in highly utilized facilities where the occupants have very high expectations. Many if not most of their facilities are expected to be aesthetically and operationally at the cutting edge of technology (Odom and Parsons, 1998). Other major private sector property owners who have adopted commissioning include Westin Hotels, Boeing, Chevron, Kaiser Permanente, and Target. The U.S. General Services Administration has taken steps to integrate commissioning into its design and construction program. State and local governments have also been leaders in the move toward commissioning, with significant programs at the state or local level in Florida, Idaho, Maryland, Montana, New York, Oregon, Tennessee, Texas, and Washington (Haasl and Wilkinson, 1998). The Commissioning Process Perhaps the major reason that commissioning is needed is that in many projects, “commissioning” the project simply consists of turning everything on and verifying that all motors, chillers, and boilers run. The HVAC commissioning process ideally begins during the building programming phase and continues through the design phase, the construction phase, the acceptance phase, and into a post acceptance phase. It requires the participation of the owner (or representative), the commissioning coordinator (commissioning authority), the design professionals, and the construction manager. There is considerable agreement that a strong commissioning program requires a commissioning coordinator, often called the commissioning authority. The commissioning authority is the person or company who implements the overall commissioning process and coordinates commissioning related interactions between

the other parties involved in the design, construction, and commissioning process. The commissioning authority (CA) reports to the owner and works with the other design professionals during the project. The construction manager then has primary responsibility for ensuring that the various contractors carry out the intent of the design developed, with the CA providing a detailed verification that the project, as built, does in fact meet the design intent. To maximize the benefits of commissioning, the owner selects the CA early in the programming phase so they can develop a preliminary commissioning plan before the design phase begins. During the design phase, the principal responsibility of the CA is to review and comment on the design as it evolves and update the commissioning plan as necessary. During the construction phase, the full commissioning team comes on board, and training of the building staff begins, while the CA continues to closely observe the construction process. The major commissioning activity does occur during the acceptance phase, with a multitude of checks and tests performed, further staff training, and finally, reporting and documentation of the process. The new commissioning process for new buildings has been described in more detail in many places, including ASHRAE (1996) and Claridge and Liu (2000). The remainder of this paper will be devoted to the commissioning of existing buildings. Commissioning Existing HVAC Systems In buildings that are not commissioned, numerous problems are identified and corrected over time, but many are more subtle and are never identified or corrected. Problems with sensor and actuator calibration, damper leakage, control strategies, etc. tend to remain hidden, and the operators are generally unaware that they exist unless they lead to a comfort complaint. Other problems may be known to the operators, but their significance can go unrecognized, so they are not corrected. Examples include higher air-side and water-side pressures than needed, inefficient hot-deck and cold-deck set-points, reset ranges, etc. Operators and maintenance personnel often increase consumption when dealing with an immediate problem, e.g. by lowering chilled water supply temperature in response to a hot call. Buildings are modified almost continuously in response to changes in tenants, remodels for existing tenants, changes in use of a space, etc. These changes may be accompanied by band-aid changes to the HVAC system, but often lead to further inefficiency. Consequently, there is tremendous opportunity for commissioning to benefit existing buildings. The commissioning of existing buildings has been called retrocommissioning (commissioning of an existing building that has never been commissioned) and recommissioning (commissioning an existing building

subsequent to one or more previous commissioning processes). Whatever it may be called, commissioning of existing buildings is intended to identify any unresolved problems that occurred during construction, just as commissioning does in a new building, and to go beyond this point to identify and correct problems that have developed during subsequent operation of the building. Benefits of Commissioning Existing Buildings The specific benefits of commissioning existing buildings have been enumerated by Haasl and Sharp (1999) as follows: 1. Identifies system operating, control and maintenance problems 2. Aids in long-term planning and major maintenance budgeting 3. Helps ensure a healthy, comfortable, and productive working environment for occupants 4. Reduces energy waste and ensures that energy-using equipment operates efficiently 5. Provides energy cost savings that often pay back investment. 6. Reduces maintenance costs; reduces premature equipment failure 7. Provides complete and accurate building documentation; expedites troubleshooting 8. Provides appropriate training to operating staff to increase skill levels; increases staff effectiveness in serving customers or tenants 9. Reduces risk and increases the asset value of the building One study found that commissioning of existing buildings is very attractive economically, even if the only benefit considered is energy savings. Gregerson (1997) presented results from commissioning of 44 existing buildings that showed simple paybacks which ranged from 0.1 years to 4.2 years, with 28 having a payback of less than one year, 12 between 1.0 and 2.0 years and only 4 had a payback longer than 2.0 years. The buildings in this study were generally large buildings, with the smallest having 48,000 ft2, and only 12 were less than 100,000 ft2. Energy use in these buildings was reduced by 2% to 49% with an average reduction of 17.5%. The cost of commissioning was quite evenly distributed over the range from U.S. $0.03/ft2 to U.S. $0.43/ft2 with 11 buildings less than U.S. $0.10/ft2 and nine at more than U.S. $0.30/ft2. Procedures for Commissioning Existing Buildings In 1999, the U. S. Department of Energy (DOE) developed a practical guide for commissioning existing buildings (Haasl and Sharp 1999). While this guidebook discusses several building commissioning processes including new building commissioning, it emphasizes retro-commissioning. The main purpose of the retrocommissioning process is to solve existing problems in

buildings where new building commissioning was not conducted and to operate the building efficiently and effectively. Retro-commissioning primarily focuses on operation and maintenance (O&M) issues and solves existing problems using commonly available technical or operational solutions. The Continuous CommissioningSM (CCSM)1 process developed by the authors and emphasized in the description of commissioning procedures for existing buildings that follows is somewhat different from retrocommissioning and new building commissioning in its goals, methods, and results. The goals of the CC process are to optimize the HVAC system operation and control to minimize building energy consumption and to maximize comfort based on the current building conditions and requirements. The design intent is considered only as a reference, not as the performance target, realizing that (1) the building designer rarely has enough information to specify optimal operation of the design, and (2) the building function and use have often changed significantly from original expectations. The CC process is not limited to solving O&M problems. It focuses on innovative engineering solutions using state-of-the-art technologies. For example, calibrated simplified engineering models are used to identify system faults and to develop optimal operation schedules (Liu and Claridge 1998, 1999). The CC process has resulted in an average energy reduction of over 20% in 130 buildings (Liu et al. 1994, 1999a, Claridge et al. 1994, 2000) with simple paybacks typically less than two years. Innovative engineering solutions have been used to solve numerous engineering problems (Liu et al 1999b, Wei et al. 2002) that have eliminated or greatly reduced retrofit savings. The CC process maintains long-term savings by monitoring and verifying energy savings using dedicated meters and/or building automation systems. The CC process also upgrades the operating staff’s skills by allowing direct participation of O&M staff, as well as reducing O&M costs. Continuous Commissioning is an ongoing process to resolve operating problems, improve comfort, optimize energy use and identify retrofits for existing commercial and institutional buildings and central plant facilities. This statement defines the objectives and scope of the CC process, but does not indicate how the process is implemented. Any CC project must initially go through a project development phase in which the CC project scope is clearly defined and a contract is signed. This phase typically involves a CC audit followed by a proposal leading to a contract, which differs little from a normal 1

Continuous Commissioning and CC have been service marked by the Energy Systems Laboratory of the Texas A&M University System to ensure a consistent meaning for these terms as used in this paper.

retrofit project except in terms of the measures identified in the audit. Hence, it will not be discussed further. During the second phase of the CC process, the CC measures identified in the audit are refined and implemented. This phase includes six steps: (1) develop the CC plan and form the project team, (2) develop performance baselines, (3) conduct system measurements and refine proposed CC measures, (4) implement CC measures, (5) document comfort improvements and energy savings, and (6) keep the commissioning continuous. Step 1: Develop the CC plan and form the project team The objective is to develop a detailed work plan with a qualified team that includes a project manager, at least one CC engineer, one or more technicians and at least one member of the facility staff. When the work plan is developed, the following issues have to be considered: (1) the availability of funding for replacing/repairing broken parts, (2) the time commitment of in-house staff, and (3) the training needs of in-house staff. Step 2: Develop performance baselines The objectives are to document existing comfort and system conditions, and to develop baseline energy consumption models. Documentation of comfort conditions emphasizes existing comfort problems, e.g. areas that are too cold, too hot, too noisy, or too humid. The documentation of system conditions focuses on system operation problems such as valve and damper hunting, disabled mechanical and control systems or components, frequently replaced parts, and simultaneous heating and cooling. This is often done through detailed field measurements and inspections using skilled engineers or technicians. Baseline models of building energy performance are necessary if energy savings are to be documented after the building is commissioned. The energy baseline models normally developed include whole building electricity, cooling energy, and heating energy models. The energy baselines can be determined from regression models or a calibrated simulation program. Regression models typically express energy consumption as a function of outside air temperature. Baseline models can be developed from one or more of the following types of data: (1) shortterm measured data obtained from data loggers or the EMCS system; (2) long-term hourly or 15-minute whole building energy data, such as whole building electricity, cooling and heating consumption, and/or (3) data from utility bills for electricity, gas, and/or chilled or hot water. Techniques used to determine savings should be consistent with the International Performance Measurement and Verification Protocol (IPMVP 2001) and/or ASHRAE Guideline 14 (ASHRAE 2002).

Step 3: Conduct System Measurements and Develop CC Measures The objectives are to (1) identify current operating schedules and problems, (2) develop solutions to existing problems, (3) develop improved operation and control schedules, and (4) identify potential cost-effective energy retrofit measures. Detailed measurements are conducted to investigate the accuracy of sensors, the condition of actuators, and control schedules. Detailed engineering analysis is conducted, based on the measured data collected, to develop solutions for the existing problems; improved operation and control schedules are developed for terminal boxes, air handling units (AHUs), exhaust systems, water and steam distribution systems, heat exchangers, chillers, boilers, and other components as appropriate. Potential cost-effective energy retrofit measures are identified and evaluated. Step 4: Implement CC Measures The objectives are to (1) obtain approval for each CC measure from the building owner’s representative prior to implementation, (2) solve existing operational and comfort problems, and (3) implement and refine improved operation and control schedules. The building owner’s representative and building staff must be comfortable with each CC measure implemented or the measure will be quickly disabled. Measures should be modified if necessary to obtain staff buy-in. Implementation should start by solving existing problems. Difficult comfort and control problems are the first priority of the occupants, operating staff, and facility owners. Solving these problems improves occupant comfort and increases cooperation from operating staff. The economic benefits of comfort improvements are sometimes greater than the energy cost savings, though less easily quantified. Implementation of the improved operation and control schedules should start at the end of the comfort delivery system, such as at the terminal boxes, and should end with the central plant. This procedure provides benefits to the building occupants as quickly as possible. It also reduces the overall working load on the plant. If the process is reversed, the chiller plant is commissioned first and the chiller sequences are developed based on the current load. After building commissioning, the chiller load may be decreased by 30%. The chiller operating schedules are then very likely to need revision. Step 5: Document comfort improvements and energy savings The objectives are to (1) document improved comfort conditions, (2) document improved system conditions, and (3) document improved energy performance. The comfort measurements taken in step 2 should be repeated at the same locations under comparable conditions to determine

commissioning impact on room conditions. The measured parameters, such as temperature and humidity, should be compared with the results of step 2. The measurements and methods adopted in step 2 should be used to evaluate post CC energy performance. Energy performance should be compared using appropriate occupancy and weather normalization (IPMVP 2001, ASHRAE 2002). Typically, building energy consumption is regressed as a function of outside air temperature if annual projections are desired from short-term data. Step 6: Keep the Commissioning Continuous The objectives are to (1) maintain improved comfort and energy performance, and (2) provide measured annual energy savings through ongoing help from CC experts, who may provide follow-up phone consultation, review the energy data, and monitor and analyze system operation through the Internet or other remote means as needed. One year after initial CC implementation is complete, the CC engineer should write a project follow-up report that documents the first-year savings, recommendations or changes resulting from any consultation or site visits provided, and any recommendations to further improve building operations. Subsequent follow-up should be provided when energy use increases or difficult comfort problems occur (Claridge et al. 2002). CC Measures The CC process implements measures ranging from typical “improved O&M” measures to innovative engineering measures (Liu et al. 2002). “Improved O&M” measures refer to good operating practices such as shutting off systems at night and repairing malfunctioning components. These measures align the building systems with design requirements and specifications adapted to current building use. The innovative engineering measures can be grouped into two categories: control optimization measures and system modifications. The control optimization measures focus on optimizing operating schedules such as schedules for maximum airflow, minimum airflow, supply air temperature and static pressure, supply water temperature and differential pressure, primary/secondary loop pump control, and parallel pump control and are described in detail in Liu et al. (2002). The implementation of these control optimization measures requires a high level of engineering skill and results in significant energy savings. The innovative system modification measures integrate minor system retrofits with the control measures to achieve additional system optimization and savings (Liu et al. 2003). These measures are not typical energy conservation retrofit measures. Since the capital requirement for these measures is small, the payback for these measures is

routinely three years or less, similar to that of other CC measures.

building is heated and cooled by two (2) single duct variable air volume (VAV) air handling units (AHU) each having a pre-heat coil, a cooling coil, one supply air fan (100 hp), and a return air fan (25 hp). Two smaller constant volume units handle the teaching/lecture rooms in the building. The campus plant provides chilled water and hot water to the building. The two (2) parallel chilled water pumps (2×20 hp) have variable frequency drive control. There are 120 fan-powered VAV boxes with terminal reheat in 12 laboratory zones and 100 fan-powered VAV boxes with terminal reheat in the offices. There are six (6) exhaust fans (10-20 hp, total 90 hp) for fume hoods and laboratory general exhaust. The air handling units, chilled water pumps and 12 laboratory zones are controlled by a direct digital control (DDC) system. DDC controllers modulate dampers to control exhaust airflow from fume hoods and laboratory general exhaust. A CC investigation was initiated in the summer of 1996 due to the extremely high level of simultaneous heating and cooling observed in the building (Abbas, 1996). Figures 1 and 2 show daily heating and cooling consumption (expressed in average kBtu/hr) as functions of daily average temperature. The Pre-CC data heating given in Figure 1 shows very little temperature dependence as indicted by the regression line derived from the data. Data values were typically between 5 and 6 MMBtu/hr with occasional lower values. The cooling data (Figure 2) shows more temperature dependence and the regression line indicates that average consumption on a design day would exceed 10 MMBtu/hr. This corresponds to only 198 sq.ft./ ton based on average load.

Cases Where Continuous Commissioning May Be Used The CC process has been applied almost exclusively to buildings with a floor area of at least 50,000 ft2. About 90% of the buildings to which the process has been applied are in cooling dominated climates where typical cooling consumption in large buildings is at least two times the heating consumption. However, it has also been successfully applied to buildings in the coldest parts of the continental United States. It is a relatively labor intense process at this time, making it generally more applicable to buildings with large air handlers and large total energy use. Automated control systems tend to simplify implementation of CC and it has been particularly effective in buildings that exhibit significant simultaneous heating and cooling. If the CC process were to be implemented in all in the commercial buildings larger than 50,000 ft2 in the United States, and achieve comparable savings, it would have the potential to reduce consumption in the commercial buildings sector by 8%. Of course, if it were successfully implemented on that scale, it can be anticipated that a variety of automated techniques would make it applicable to smaller buildings and expand the potential impact. Case Study - Kleberg Building The Kleberg Building is a teaching/research facility on the Texas A&M University campus consisting of classrooms, offices and laboratories, with a total floor area of approximately 165,030 ft2. Ninety percent of the

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Figure 2. Pre-CC and post-CC cooling water consumption at the Kleberg Building vs. daily average outdoor temperature. It was soon found that the preheat was operating continuously, heating the mixed air entering the cooling coil to approximately 105˚F, instituted in response to a humidity problem in the building. The preheat was turned off and heating and cooling consumption both dropped by about 2 MMBtu/hour as shown by the middle clouds of data in Figures 1 and 2. Subsequently, the building was thoroughly examined and a comprehensive list of commissioning measures was developed and implemented. The principal measures implemented that led to reduced heating and cooling consumption were: • Preheat to 105˚F was changed to preheat to 40˚F • Cold deck schedule changed from 55˚F fixed to vary from 62˚F to 57˚F as ambient varies from 40˚F to 60˚F • Economizer – set to maintain mixed air at 57˚F whenever outside air below 60˚F • Static pressure control – reduced from 1.5 inH2O to 1.0 inH2O and implemented night-time set back to 0.5 inH2O • Replaced or repaired a number of broken VFD boxes • Chilled water pump VFDs were turned on. Additional measures implemented included changes in CHW pump control – changed so one pump modulates to full speed before second pump comes on instead of operating both pumps in parallel at all times, building static pressure was reduced from 0.05 inH2O to 0.02 inH2O, and

control changes were made to eliminate hunting in several valves. It was also observed that there was a vibration at a particular frequency in the pump VFDs that influenced the operators to place these VFDs in the manual mode, so it was recommended that the mountings be modified to solve this problem. These changes further reduced chilled water and heating hot water use as shown in Figures 1 and 2 for a total annualized reduction of 63% in chilled water use and 84% in hot water use. Additional follow-up conducted from June 1998 through April 1999 focused on air balance in the 12 laboratory zones, general exhaust system rescheduling, VAV terminal box calibration, adjusting the actuators and dampers, and calibrating fume hoods and return bypass devices to remote DDC control (Lewis, et al. 1999). These changes reduced electricity consumption by about 7% or 30,000 kWh/mo. In 2001 it was observed that chilled water savings for 2000 had declined to 38% and hot water savings to 62% as shown in Table 1. Chilled water data for 2001 and the first three months of 2002 are shown in Figure 3. The two lines shown are the regression fits to the chilled water data before CC implementation and after implementation of CC measures in 1996 as shown in Figure 2. It is evident that consumption during 2001 is generally appreciably higher than immediately following implementation of CC measures. The CC group performed field tests and analyses that soon focused on two SDVAV AHU systems, two chilled water pumps, and the Energy Management Control System (EMCS) control algorithms as described in Chen et al. (2002). Several problems were observed as noted below.

Table 1. Cooling water and heating water usage and saving in the Kleberg Building for three different years normalized to 1995 weather. Type CHW HW

Pre-CC Baseline (MMBtu/yr) 72935 43296

Post-CC Use/Savings Use (MMBtu/yr) Savings (%) 26537 63.6% 6841 84.2%

Problems Identified

• VFD control on two chilled water pumps was again by passed to run at full speed. • Two chilled water control valves were leaking badly. Combined with a failed electronic to pneumatic switch and the high water pressure noted above, this resulted in discharge air temperatures of 50F and lower and activated preheat continuously. • A failed pressure sensor and two failed CO2 sensors put all outside air dampers to the full open position. • The damper actuators were leaking and unable to maintain pressure in some of the VAV boxes. This caused cold air to flow through the boxes even when they were in the heating mode, resulting in simultaneous heating and cooling. Furthermore some of the reheat valves were malfunctioning. This caused the reheat to remain on continuously in some cases. • Additional problems identified from the field survey included the following: 1) high air resistance from the filters and coils, 2) errors in a temperature sensor and static pressure sensor, 3) high static pressure set points in AHU1 and AHU2. A combination of equipment failure compounded by control changes that returned several pumps and fans to constant speed operation had the consequence of increasing chilled water use by 18,894 MMBtu and hot water use by 9,510 MMBtu. This amounted to an increase of 71% in chilled water use and more than doubled hot water use from two years earlier These problems have now been largely corrected and building performance has returned to previously low levels as illustrated by the data for April-June 2002 in Figure 3. This data is all below the lower of the two regression lines and is comparable to the level achieved after additional CC measures were implemented in 1998-99.

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Figure 3. Cooling water data for the Kleberg Building since January 2001. When Is Follow-Up Commissioning Needed? For the Kleberg Building, it is clear that a combination of control changes and component problems led to a need for follow-up commissioning measures. In principle, these measures could be viewed as routine maintenance, but since they had not led to comfort problems, it is unlikely that they would have been addressed unless they ultimately resulted in a comfort problem. Even then without the evidence of the $66,500/year increase in consumption, it is unlikely that a comprehensive follow-up effort would have occurred. But how often do such problems occur? The ESL has conducted a study of 10 buildings on the A&M campus that had CC measures implemented in 199697. Table 2 shows the baseline cost of combined heating, cooling and electricity use of each building and the commissioning savings for 1998 and 2000. The baseline consumption and savings for each year were normalized to remove any differences due to weather (see Turner, et al. 2001 for details). Looking at the totals for the group of 10 buildings, savings decreased by over $207,258 (17%) from 1998 to 2000, but were still very substantial. However, it may also be observed that almost ¾ of this decrease occurred in two buildings, the Kleberg Building, and G. Rollie White Coliseum. The increased consumption of the Kleberg Building was due to a combination of component failures and control problems as already discussed. The increased consumption in G. Rollie White Coliseum was due

Table 2. Commissioning savings in 1998 and 2000 for 10 buildings on the Texas A&M campus. Building Kleberg Building G.R. White Coliseum Blocker Building Eller O&M Building Harrington Tower Koldus Building Richardson Petroleum Building Veterinary Medical Center Addition Wehner Business Building Zachry Engineering Center Totals

Baseline Use ($/yr) $ 484,899 $ 229,881 $ 283,407 $ 315,404 $ 145,420 $ 192,019 $ 273,687 $ 324,624 $ 224,481 $ 436,265 $ 2,910,087

to different specific failures and changes, but was qualitatively similar to Kleberg since it resulted from a combination of component failures and control changes. The five buildings that showed consumption increases above 5% from 1998 to 2000 were all found to have different control settings that appear to account for the changed consumption (including the decrease in the Wehner Business Building). This data does not explicitly answer the question “When is follow-up commissioning needed?”, but the authors believe it suggests that tracking consumption and investigating the reasons for significant increases is likely to provide real benefits. Existing Buildings Commissioned There have been no comprehensive surveys of the extent of commissioning of existing buildings. The proceedings of the National Conference on Building Commissioning from 1996 – 2001 were scanned to identify the basic characteristics of commissioned buildings as reported in case studies or papers that gave sufficient information to determine the size and use of different existing buildings that have been commissioned in the U.S. and Canada in recent years. Table 3 summarizes the findings of this effort. Three fourths of the buildings and over 85% of the area commissioned were offices and medical facilities. Some of the offices reported here are private buildings, but many are public sector buildings, including some that include classroom space on university campuses. The “Lab./Office” category shown in Table 3 is primarily public sector buildings that include substantial laboratory space, but generally include significant office space as well.

1998 Savings ($/yr) $ 313,958 $ 154,973 $ 76,003 $ 120,339 $ 64,498 $ 57,076 $ 120,745 $ 87,059 $ 47,834 $ 150,400 $ 1,192,884

2000 Savings($/yr) $ 247,415 $ 71,809 $ 56,738 $ 89,934 $ 48,816 $ 61,540 $120,666 $ 92,942 $ 68,145 $127,620 $ 985,626

Table 3. Summary of the area and types of existing buildings reported as commissioned in the Proceedings of the National Conference on Building Commissioning: 1996 – 2001 (NCBC 1996 – 2001). Building Use Office Retail Lab./Office Library Medical School Gym Total

Number Commissioned 38 6 7 2 22 4 1 80

Area (ft2) 9,509,213 1,053,238 912,711 187,380 7,514,488 312,489 177,838 19,667,357

Of the total of 19,667,357 ft2 of space commissioned, only 4,333,238 ft2 is clearly privately owned. Another 1,595,000 ft2 did not have ownership clearly specified. 13,739,119 ft2, or about 70% of the total area commissioned was owned by various public entities. Clearly, this does not constitute the total area that has been commissioned in the existing buildings sector. The amount or thoroughness of commissioning that has occurred in these buildings also varies considerably. We estimate that 100 million to 200 million ft2 of existing commercial buildings have received some form of retrocommissioning. We also expect that the sample above is skewed more heavily toward the public sector than the total set of commissioned buildings. It is also probable that a larger fraction of existing public sector buildings have been commissioned than is true of private sector buildings. The commercial sector in the United States includes 67.3 billion ft2 of floor space (EIA 1999) and 41.1 billion ft2 of this is in buildings of 25,000 ft2 or larger, which constitutes the vast bulk of the buildings reported as retrocommissioned to date. Hence, it would appear that even the upper limit of our estimate suggests that considerably less than 1% of the larger buildings in the commercial sector have yet been retro-commissioned.

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