It is Time to Learn How Buildings Actually Perform

how buildings actually perform
Brian McCowan for Zondits, May 15, 2015. Image credit: gr8effect

The move toward outcome-based building performance assessment and code compliance is a major step forward for energy efficiency efforts. The outcome-based methodology is so logical, in fact, that most people outside this industry already assume that the energy performance of commercial buildings, and especially those that have benefitted from rate-payer funded efficiency programs, is determined by measuring the actual performance. With the recent and current advancements in metering, it is time for the efficiency industry to seriously question why extensive predictive modeling and the performance evaluation of a small statistical sample of buildings should not be replaced by simply measuring and evaluating the performance of operating buildings. The Getting to Outcome-Based Performance report published by the National Institute of Building Sciences (NIBS) and the New Buildings Institute (NBI), makes a compelling case for making this transition.

Energy code compliance is an area that would benefit greatly from outcome-based performance evaluations. ERS has conducted hundreds of energy code trainings for code officials and design professionals. In addition, we have conducted several code compliance studies which included extensive interviews of code officials. It has been clearly demonstrated that the energy code for commercial buildings has become too complex and expansive to be effectively enforced. Code officials are very busy with a variety of life-safety codes, and they have backgrounds that are primarily focused on residential construction.

Commercial building energy codes generally include two compliance paths: prescriptive and predictive performance. The prescriptive path assumes that a set of design features and equipment installations will be appropriate for the building, correctly installed, properly commissioned, and will operate as intended. Performance paths require that two building designs be configured: one that represents the proposed design, and a second (base) design of the same size the meets the code prescriptive requirements. The two designs are modeled for hourly performance and the proposed design must be predicted to use no more energy than the base design. Neither path has been proven to be particularly accurate, and the predictive performance path is especially vulnerable to mistakes and or intentional manipulations that are extremely hard to detect.

High performance commercial new construction programs target efficiency levels better than code minimums, but are, in fact, based on the same procedures used for code compliance. Some simply require performance better than code by some percentage, while others establish an alternative set of prescriptive requirements. Outcome-based performance evaluation would improve compliance and ultimately performance for participant projects, just as it would for code compliance.

A major reason for resisting outcome-based performance evaluation in the past has been the expense and complexity of metering multiple end uses of electricity and fossil fuel usage. However, metering technology is advancing fast, and by the time outcome-based strategies become widely adopted, the next wave of monitoring technologies, including wireless metering with cloud connectivity, will be readily available. Monitoring systems with user dashboards are already in use in many facilities and it’s an obvious next step to begin monitoring the actual performance of the buildings we design and construct.