Chief Engineers & Facility Managers Conference: Retrocommissioning

Buildings need tune-ups, and F&S’ cross-disciplinary retrocommissioning (RCx) teams do important work to make sure utilities and systems are doing what they should and working correctly… including at the right times.

RCx teams at F&S are made up of eight people: two electricians, two temperature control mechanics, two sheet metal workers, one engineer, and one programmer.

Andy Robinson, energy services administration engineer, gave a talk detailing how his team completed work and changed systems at Sidney Lu Mechanical Engineering Building. Most of the building is teaching space with some offices and mechanical labs that required typical energy tune-ups.

Robinson and his interdisciplinary team dug through utility and energy usage data to find higher than average energy use and a cleanroom kept to higher standards than the typical office or teaching space. Even by cleanroom standards, this ‘yellow room’–named for its yellow lighting–was practically spotless… or “particle-less.”

Hello Yellow Room

The goals of the cleanroom and those who use them are important, as Robinson recounted.

“They want that room to get to 65 degrees Fahrenheit with 30-55% relative humidity (Rh), which in the summer, is really cold and dry,” Robinson said. “It’s a big energy use in that space, including a 75-horsepower fan using a lot of power. It’s about 580 square feet and used only two afternoons per week. In general, the 12 people ‘max occupancy’ is only reached two afternoons per week. It’s sporadic use in this space.”

Per the Grainger College of Engineering, the space is for “research in the design and fabrication of small-scale mechanical systems. The lab supports research and instruction in the general area of micro- and nano-electro-mechanical systems (MEMS & NEMS), and nano-chemical-electrical-mechanical-manufacturing systems (Nano-CEMMS). The current focus is on devices employing nano-to-microscale mechanisms and the integration of these mechanisms into meso-scale devices.”

Robinson also noted how energy experts might tighten up at the mention of a cleanroom.

“When the word ‘cleanroom’ comes up, everyone buttons up and becomes very conservative. You just take baby steps. Just try one change at a time, not a wholesale change all at the same time.”


What the RCx team decided to do was based on that relatively rare room use: the primary cooling coil was being used fully and completely, seemingly all the time; and airflow was measured at about 400 ‘air changes per hour,’ which Robinson called “an enormous” amount per hour in that amount of space and nearly twice what this class of room required.

By reducing the fan from 75 to 20 horsepower, airflow lessened and the cooling coil and rooftop sub-chiller reduced, but the room has remained cold and clean, even for cleanroom standards. People are what make a cleanroom dirty, so adding occupancy sensors allow the fans to slow down even more at night.

Robinson said now the fan runs at 65% power when occupied and 30% when unoccupied. This, and reducing the power of the fan, will avoid approximately $35,000-50,000 of electricity and cooling costs. Further savings could be achieved with automatic particle counters, but these are costly and require expensive calibration.

A handheld particle counter had to be re-, double-, and triple-checked when data first came in. Eventually, testers realized the room is extremely clean.

“It’s an ultra cleanroom,” Robinson concluded.

Robinson’s top 11 ways to avoid cost and save energy.

  • Schedule units off when building is closed
  • Calibrate AHU sensors (temp, humidity, pressure, CO2)
  • Check outdoor air dampers (tight bolts, tune actuators)
  • Check for simultaneous heating and cooling
  • Check that Supply Air Temp and Pressure resets are working
  • Go through each room – lighting, CO2 and Temp sensors, calibrate VAVs, reduce reheat valve leakage
  • Reduce outdoor air and exhaust
  • Look for motors or pumps that can turn down or need VFD
  • Add steam isolation valves to disable steam radiators in summer
  • Identify constant volume reheat that could be variable volume
  • Add or upgrade digital controls