Editor's note: Following is Part 2 in a three-part series.
Read Part 1: A Vision for Energy Performance
Accountability is key for the success of any strategy aimed at a large-scale improvement in building energy performance. A properly developed industrywide policy on energy-performance accountability will attract new, more-efficient energy technology to the industry and ensure that it is applied and supported effectively. Because of the fragmented structure of the various entities that make up the buildings industry and the nature of the utilities that serve it, developing energy accountability is not a simple matter. To accept accountability, one generally must have some authority or control over the technology and processes involved throughout the design, implementation, and operation of a building.
However, designers and contractors have limited control over aspects beyond their scope during the construction process and usually no control over buildings once they are occupied and operating. It is the building owner who wields ultimate control over the design and construction of energy systems in new buildings or the acceptance of those systems in a purchased building. Furthermore, it is the building owner who has primary access to ongoing metered building-energy-use information and control over operations. It is reasonable to conclude that the fundamental accountability for the energy performance of building stock should reside with building owners.
METRICS FOR MEASURING ENERGY PERFORMANCE
Studies have found that providing building owners with relevant and useful energy-performance and utility-pricing information leads to energy-performance improvements. So, if building-performance responsibility is defined properly, targets are set, and useful information is made available, building owners are well-positioned to dictate energy performance as a criterion in the purchase or design of buildings, as well as effectively manage the energy performance of occupied buildings.
However, if public policy puts building owners on the front lines of greater building energy efficiency, it also must provide some compensation or reward for their efforts in helping make this transition. Benefits, such as preferred energy rates or tax incentives, need to be a component of the policy for building owners who succeed in capturing energy reductions. Options for incorporating such incentives will be discussed later in this column.
If building owners are accountable for building energy performance, three key issues need to be resolved to give owners the tools to manage building energy performance more effectively. First, various building types should be held to energy-performance standards. Second, energy-performance metrics should be used to judge whether the appropriate energy-performance standards are being met. Finally, tools that allow building owners to verify performance upon the purchase or construction of a building may be required. When rated performance is not achieved, tools may be required to determine areas in need of improvement for energy use to be aligned with energy-performance standards. To be effective, each of these tools must be clear and simple to apply.
Because total-building energy use is the fundamental parameter of concern, basic energy-performance standards and metrics should be developed around the actual metered energy use of each building. When building energy use exceeds energy-performance standards, additional performance-monitoring metrics need to include more information than just utility-meter data. To provide additional performance information, public policy should require that specific performance monitoring be integrated into all building systems.
Designers, contractors, and equipment manufacturers need to incorporate adequate metrics into each new building or upgrade to ensure that all of the energy-consuming systems perform as expected when turned over to the owner. Building owners then need specific performance information to help keep each piece of equipment and system operating efficiently throughout the building's life and meet the overall building-performance standard each month.
To procure information that goes beyond utility-meter data, two categories of building-system-performance metrics need to be developed. The first category is efficiency-based information. This includes heating and cooling operating efficiency and, in some cases, air-delivery operating efficiency expressed as an overall system coefficient of performance (COP), watts per unit output, energy-efficiency ratio, or other agreed-upon and widely used term.
To ensure that an owner or operator can diagnose and correct building-operation problems when energy use begins to climb, a second use-based metrics category should include heating, cooling, air delivery, lighting, and plug-load energy use expressed in energy-use-per-unit building area, such as kilowatts or thermal units per square foot, over a variety of accounting periods, primarily monthly and annually. Also, an instantaneous peak rate of energy use for each of these categories expressed in kilowatts per square foot may be helpful.
In the event that energy use increases slowly, periodic information for each of these categories can be compared with historical use or published norms to determine which building-operation areas need attention. Ongoing building-commissioning procedures that operate with such comparisons already have been proven effective when supported properly over the long term.
The exact energy-monitoring parameters that are required will vary depending on the complexity of the building and the nature of the systems incorporated. Large commercial or industrial buildings are likely to require a full set of efficiency and use metrics that are monitored by the building-control system and compared daily or weekly with historical values to ensure ongoing building-performance compliance. Basic performance-monitoring parameters are selected to ensure owners can confirm upon their buildings' completion or purchase that the promised level of energy performance has been achieved. As the building owner assumes responsibility for operating the building systems, the performance information must be able to ensure that the building can meet its overall performance goal each month.
HPAC Engineering's Engineering Green Buildings and Commissioning Green Buildings conferences and expos will be held Oct. 21 and 22 at Mandalay Bay Resort and Casino in Las Vegas. To register, visit www.egbconference.com or www.cgbconference.com.
A member of HPAC Engineering's Editorial Advisory Board and principal of The Hartman Co., Thomas Hartman, PE, is an internationally recognized expert in advanced high-performance building-operation strategies. Among his recent innovations are the Equal Marginal Performance Principle and the development of demand-based control, which together offer an effective method to optimally configure and operate complex HVAC systems. He has lectured on advanced-technology topics at seminars around the world.
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