SE-14-C035 -- Performance-Based Building System Evaluation for DOE Energy Asset Score PDF

The Commercial Building Energy Asset Score, being developed by Pacific Northwest National Laboratory for the Department of Energy(DOE), aims to help building owners evaluate overall building energy efficiency under typical operation and occupancy conditions, defined bybuilding use type. The Asset Scoring tool, a web-based application, consists of a simplified user interface built on a centralized simulationengine--EnergyPlus. The tool analyzes the as-built physical characteristics (including building envelope, the mechanical and electrical systems),pinpoints building systems with potential for efficiency improvement , and identifies cost-effective retrofit opportunities. A pilot project with morethan 100 buildings revealed that use of whole building Energy Use index (EUI) could not adequately examine efficiency and performance ofindividual building systems. A building with a well-insulated envelope and low-efficiency HVAC equipment could, theoretically, use the sameamount of energy as a building with a poorly insulated envelope and high-efficiency HVAC equipment. For two buildings with the same energyAsset Score (based on source EUI), the system-level evaluations can give tool users insight into the system-level performance and identify buildingcomponents that need greater attention. Hence, a performance-based system evaluation method has been developed to analyze individual buildingcomponents pertaining to the building envelope, lighting, heating, cooling, and service hot water systems, as well as their interactions. Aprescriptive approach for evaluating building components, though simple to use, is often limited to single variable input comparisons. Asimulation-based performance approach has been selected as the primary system evaluation method due to the multivariate nature of most systemsexamined by the Asset Scoring tool. The performance approach compares the energy use of a building system with that of baselines. The baselinevalues are determined using the DOE Commercial Building Models (Thornton et. al 2011). A series of performance ranges for different buildinguse types are developed from the highest and lowest energy use obtained by modeling the prototype buildings available for similar use types, typicallywith the ASHRAE Standard 90.1-2004 model defining the lower limit performance and the 90.1-2010 model defining the higher limit. Abuilding system is ranked by being compared to the predefined performance ranges. For example, a system falling within the range is considered"good." This methodology allows a high level of flexibility and considers a building as an integrated system.