Benchmarking is an everyday practice that allows us to understand how well a building is performing against our expectations. We can compare a building’s performance to similar buildings or against a defined performance level. For example, benchmarking can verify that a lighting retrofit completed two years earlier is delivering the anticipated light output at the expected energy savings. If not, this may be an opportunity for evaluation, given that insufficient lighting may reduce the productivity of the building’s occupants, or energy saving are not what was anticipated due to control issues.
If the objective is to track a building’s performance changes or cost savings over time, a baseline is required to establish a starting point for this analysis, and the intervals between measurements should be identified. In addition to allowing comparisons, benchmarking may also help diagnose performance issues. When actual performance or savings fall outside of expected targets, it could mean that maintenance or other adjustments need to be made.
Asset versus Operational Benchmarks
Focusing on energy, there are two primary types of benchmarks: operational and asset.
An operational benchmark is a measurement of a building’s energy performance based on metered, or actual, energy consumption over a given time period. These benchmarks normalize raw energy consumption for factors including climate, occupancy level, and operating hours to enable an apples-to-apples comparison of energy efficiency against a baseline or between different properties. While operational benchmarks are influenced by a building’s structural characteristics and systems, they most often heavily reflect the energy consumed during operation in tenanted spaces and common areas. Therefore, building managers use operational benchmarks to determine whether energy efficiency is optimized in operations and management practices. Because newly constructed buildings lack historical energy-usage data, operational benchmarks apply only to existing buildings. However, tracking energy use for a new building should not be delayed, as 12 months of data is all that is typically needed to establish a benchmark.
An asset benchmark is a measurement of a building’s predicted energy performance based on physical and structural characteristics, such as its thermal envelope, mechanical and lighting systems, fenestration, and orientation. Tracking of water use is also being used as a benchmark. To create an asset benchmark, an engineer conducts an energy simulation (also known as an energy model) of the building’s design characteristics and installed systems using a set of standard operating conditions. By removing actual tenant and occupant consumption from the procedure, asset benchmarks provide a clear picture of how a building is expected to perform based only on its physical features.
Asset benchmarks are most commonly applied during the design of new construction and renovation projects, where they can guide energy-efficiency decisions during the project and help predict overall post-construction energy performance.
Asset and operational benchmarks are complementary; they help building operators optimize energy efficiency by identifying discrepancies between predicted and actual performance. However, there are major differences in the inputs and levels of sophistication needed to conduct asset and operational benchmarks.
An asset benchmark typically requires an engineer to conduct an on-site inspection of a building, review construction and design documents, and run a complex computer simulation of the building’s key characteristics under assumed operating conditions. Asset benchmarks may take between a few days and several weeks to complete, depending on the level of detail needed.
An operational assessment is much less technical than an asset benchmark and much faster to conduct. The key pieces of information for most operational benchmarks include historical energy consumption data and a few nontechnical building and space-use metrics, such as square footage, operating hours, the number of occupants, and primary space-use classification. Several software programs allow building operators to generate their own operational benchmarks.
Globally, buildings consume approximately 40 percent of primary energy, or raw fuel. While designing and constructing buildings with energy-efficient features is important, the most significant opportunities for energy efficiency occur once construction is complete. Even when buildings are constructed to be energy efficient and comply with requirements in local building energy codes, poor operation and maintenance during a building’s life span can result in significant underperformance.
Informed Energy-Efficiency Investments
Benchmarking represents the process of understanding the current status and position within a specific environment, as compared to an established standard. The ability to quantify changes, both favorable and unfavorable, as they are influenced by operations helps explain how implemented strategies are performing. Investors use the information obtained from benchmarking to evaluate the effectiveness of any energy-efficiency investments made, and to determine if corrective action is required when the results are not as expected. This assessment is critical for goals that are significant or important to the organization. Benchmarking is not just a data collection exercise; instead, the aim is to deliver actionable information to the user. There are many industry tools available to building management to meet benchmarking needs and requirements.
Three Types of Benchmarking Tools
Benchmarking tools are any resources that support efforts to benchmark an activity. These tools can be devices, rating systems, or operational behaviors. As an example, mechanical and electrical devices such as meters and sensors may be used as benchmarking tools. Other examples include rating systems that may be used to track operating results or to translate performance levels to a common standard. Finally, there are operational behaviors, such as timely verification or updating of actions and activities, which are essential for benchmarking efforts to be successful.
This article is adapted from BOMI International’s High-Performance Sustainable Building Investments, part of the new High-Performance Sustainable Buildings credential (BOMI-HP™). More information regarding this course or the BOMI-HP™ credential is available by calling 1-800-235-2664. Visit BOMI International’s website, www.bomi.org.