Complexity: Is it worth it?
Year after year, designers and owners have pushed to safely reduce the energy consumption of labs. They have added increasing numbers and types of systems and controls, and expect multifaceted algorithms to wring more and more Watts out of a lab’s energy performance. This extended abstract on a presentation delivered at the annual I2SL Conference explores the results of a study of three lab buildings on the Tempe campus of Arizona State Univ. (ASU) to help determine if differing levels of complexity was worth the investment.
Our first step was to define complexity and identify how to measure it. We looked at things we could measure, such as the number of devices that required maintenance. But this count was too subjective—do you count safety showers, as they require annual testing? We looked at the number of air valves and terminal units, but realized that approach excluded some mechanical, plumbing and electrical systems. We tried to isolate systems that only served labs, but couldn’t easily extract that data. We then settled on the total number of hard-wired and software points in the building’s control systems. To establish a normalized metric, we divided the total number of control points by the total building area and multiplied by 1,000 to resolve the fraction. Thus, a lab with 10,000 total control points and a gross area of 100,000 sf has a “complexity factor” of 100.
ASU Interdisciplinary Science Building 1 (ISTB 1) was constructed and occupied in 2005. Its 193,294 sf includes 23% of lab space for research, imaging and a large data center. It’s a relatively simple building with a constant volume lab air management system, with very few resets. The control system utilizes 10,690 soft and hard-wired control points. The Complexity Factor for this building is calculated at 10,690/193,294 x 1000 = 55. The 2014 energy cost was $2,098,157 or $10.85/year and 608 kBtu/sf/year. This building is considered relatively uncomplicated and serves as the baseline for complexity and energy usage comparison.
ASU Biodesign Institute, also constructed in 2005, is moderately complex with a full variable volume air system and an Aircuity active air quality control system that was retrofitted the second year of operation. It houses a large special-use research lab, BSL-3 and is 100% wet lab. The lab comprises 29% of the building, which is 363,019 gsf. With 23,825 control points, the Complexity Factor is calculated at 23,825/363,019 x 1000 = 66. With a 2014 energy cost of $2,535,260, or $6.89 and 388 kBtu/sf/year.
ASU’s ISTB 4 was constructed in 2011 and occupied in 2012. It is very complex with 10 air management systems with labs (including five cleanrooms) accounting for just over 31% of the 327,256-gsf building area. It has 29,052 control points of which 80% are software points used for metering, monitoring and resets. This puts the Complexity Factor at 29,052/327,256 x 1000 = 89. With a 2014 Energy cost of $2,197,604, or $6.72 and 372 kBtu/sf/year.
As shown in Figure 1, when compared against the relatively simple ISTB-1, the Biodesign Institute used about $1,405,000 less in energy in 2014. With 3,748 more control points, it provides a savings of $374/control point. When compared against the relatively simple ISTB-1, ISTB-4 used $1,353,000 less energy in 2014. With 18,362 more control points, it provides a savings of $124/control point. At $1,500/control point, the Biodesign Institute’s added complexity has a simple payback of four years. ISTB 4, on the other hand, is currently providing a 12-year simple payback. If ISTB-4 was performing as designed, it would provide a simple payback of six years.
The bottom line is to determine whether added complexity is worth it, you must first determine if the owner can afford to invest two to three years in the fine-tuning of the systems that wring the energy costs out of the building then continue a high level of operations for the life of the building. If the answer is yes, then the complexity is certainly worth it as millions of dollars can be saved in utility costs every year.
James Wermes is a Principal Mechanical Engineer at HDR Architecture whose 40 years of experience has focused on sustainable design.