Cleanrooms and labs are energy-intensive spaces, with significant opportunities for improved efficiency. However, their inherent complexities create unique challenges to maintain the required environmental performance when combined in a single facility—in this case, the 100,000/10,000/1,000/100 cleanroom classification lab environments at the NASA Langley Research Center (LaRC) Measurement Systems Laboratory (MSL).
The program yielded of a wide range of lab types: laser/calibration/sensor, chemistry, electronics, prototyping, cleanrooms and special labs, which include a machine shop, mechanical/electrical fabrication labs and a high-intensity radiated fields lab. In order to allow for manageable change and adaption over time, the lab complex was made flexible by utilizing 12-ft x 24-ft modular lab units. A key to the planning was grouping labs with similar environmental requirements, rather than simply keeping departments or branches collocated. This non-territorial approach was instrumental in creating efficient labs and mechanical systems. Furthermore, it was an important move to encourage collaboration and cross-pollination of ideas. Bringing together both the research and engineering directorates allowed groups with different drivers to learn from each other in this new, functionally diverse facility.
Lab building energy use is generally multiple times higher than a typical building because of the large volumes of outside air used to maintain indoor air quality. By contrast, cleanroom energy use is strongly dominated by large volumes of recirculated air, plus high process loads. In response, our team categorized research spaces into labs with single-pass air, labs with recirculated air and cleanrooms with various classifications. This seemingly simple approach made the most impact in overall building energy reduction.
The MSL required several tiers of classified cleanrooms, flexible research spaces, significant ceiling heights for research instruments and a 90 hBtu/sf/yr Energy Use Intensity (EUI) target. There was also a goal of LEED Silver certification, and an energy target of 30% better than ASHRAE 90.1 2007. And, of course, there was a limited budget. Our design approach included identifying areas with high energy consumption, identifying labs with minimal chemical usage, vertically stacking labs with single-pass air requirement, while defining the appropriate level of space and engineering system flexibilities. Several energy systems were evaluated, and numerous energy-conservation measures were considered in order to identify and implement the right mix of systems for this unique facility. Some of those integrated were outside air pre-conditioning via air-to-air heat exchangers; DOAS with energy-recovery, enthalpy-based economizers; desiccant wheels; VAV units; high-efficiency motors; high-efficiency chillers with VFDs; absorption chiller utilizing campus steam, cooling towers and pumps with VFDs; high-performance envelope/glazing; and sensor-controlled LED lighting.
An important air circulation challenge to overcome was lab air change rates, as this consideration has a direct impact on energy consumption. Typical labs were set at a minimum rate of 6 ACH during occupied periods, and 4 ACH during unoccupied periods, while Class 10,000 cleanrooms are at 60 ACH and 60 ACH, Class 1,000 at 200 ACH and 150 ACH, and Class 100 at 360 ACH and 240 ACH, respectively.
One significant feature introduced was integrated fan-powered plenum modules for the primary cleanroom environments, consisting of multiple fans, accessible from below, with high-efficiency brushless DC motors fully controllable with BMS connections. Cooling coils are integrated in the plenum for sensible cooling. These fan modules are an excellent option for compact/low-clearance installations and, being a pre-engineered, packaged system, it’s easier to validate.
Another technology integrated was fan wall technology air-handling units. These units have multiple fans and provide numerous benefits: greater flexibility in unit dimensions, less floor space required due to shorter fan sections and shorter supply/return air plenums, lower noise due to less turbulence and optimized energy usage. These units can have 6 to 10% higher efficiency due to fully loaded (peak efficiency) fans in part-load operation, and tend to have greater system reliability, along with simpler and quicker fan replacement and maintenance.
In the end, the annual energy savings was a key goal, and the design has tracked well in this regard. With an average benchmark data of 226.91 kBtu/sf/yr, our design resulted in the estimated actual data of 100.1 kBtu/sf/yr, representing a 55% reduction from the benchmark data. The project is also on track to qualify for Gold LEED certification.
For more information on the project, please click here.
Dave Tash is principal at AECOM. He leads the HC and life sciences engineering practice at the DC office and is the AECOM North American Lab & Pharma Market Sector leader. Edward Weaver is Vice President at AECOM and an Architecture Practice Leader in the National Capital Office in Arlington, Va.