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Think of retro-commissioning (RCx) as the built environment equivalent of fine-tuning a high-performance race car. The pit crew car chief and the building engineer are both focused on optimizing performance through controls programing and sequencing, improving energy efficiency, and taking the lead for others to follow. Not to be confused with retrofitting where outdated building equipment (or worn racing tires) are replaced, RCx targets improving the efficiency of systems and machinery already in place. And it may also extend the service life of your existing equipment.

Pole Position on North Franklin

The Formula One example in the following case study is the building at 151 North Franklin in Chicago. ESD, now Stantec, recently completed a comprehensive retro-commissioning

Thermal Chicago District Cooling System

A network of five plants positioned across Chicago provides energy-efficient cooling for over 100 downtown buildings including iconic landmarks such as the Old Main Post Office, the Chicago Board of Trade, and the Merchandise Mart. Plant number two alone houses a mammoth-sized ice maker with 45 miles of tubing and 434 cooling coils all connected in a closed-loop system to keep office workers comfortable.

This Ice Thermal Storage system makes ice at night to take advantage of lower energy costs and decreased demand on the power grid. Water is cooled to just above freezing and then piped through an interconnected infrastructure to meet cooling demands during the day. The Chicago system is the largest in North America. It provides customers with reliable and cost-effective energy solutions, improving reliability while reducing electricity demand and water consumption.

review of the 35-story, Class-A high-rise office building located in the heart of the city. The building was already in great shape boasting an advanced heating, ventilation, and air conditioning (HVAC) system with extensive control capabilities as well as a state-of-the-art dedicated outdoor air system coupled with floor-by-floor air handling units that provide efficient pre-conditioning and distribution of air throughout the facility.

Described as technically advanced, sustainable, and forward-looking, the 820,422 square-foot office tower is well-credentialed with certifications including:

  • First WELL v1 Gold Certified Core & Shell high-rise in the nation
  • WiredScore Platinum 100/100
  • LEED Gold Core & Shell Certified
  • WELL Health & Safety Certified
  • SmartScore Platinum
  • ENERGY STAR

The building also leverages Chicago’s district cooling system (see sidebar) and relies on 100 percent electric heating to minimize its carbon footprint.

Earning the Checkered Flag in Efficiency

The goal of the retro-commissioning project was twofold:

  • To identify and enhance the operational energy efficiency of the already high-performing building
  • To identify opportunities to improve the performance of the HVAC equipment and the building automation system in light of the issues of the COVID/post-COVID world

Achieving these goals was prioritized without compromising the health and comfort of the building occupants. We worked with the Buck Management Group and building engineering teams to take advantage of the ComEd Retro-Commissioning Program. This energy efficiency initiative offered by the utility facilitated the engineering study and provided reimbursements to the building for automation control upgrades based on resulting energy savings. Through this program, our team underwent a thorough examination of potential energy conservation measures within the building’s control system. These measures were identified to minimize implementation costs while maximize efficiency gains. Here are some of the opportunities we uncovered:

Reducing any isolated situation of simultaneous heating and cooling: By adjusting control strategies and addressing equipment inefficiencies, the project team successfully reduced instances of simultaneous heating and cooling, thus avoiding energy waste, and optimizing thermal comfort.

Improving unoccupied operational efficiency: Adjustments of the building automation system enabled the implementation of optimized unoccupied operation sequences, resulting in significant energy savings during periods of low occupancy.

Adjustments to energy recovery systems: By tuning and optimizing energy recovery systems, efficiency of heat exchange processes was maximized, thereby conserving energy, and reducing the building’s overall demand.

Aligning conditioning requirements with building demand: Through careful analysis of occupancy patterns and occupancy-based control strategies, the team aligned the conditioning requirements more closely with the actual building demand. This approach ensures a more efficient use of energy resources.

Optimizing outdoor air ventilation: The team recalibrated and optimized the outdoor air ventilation rates to match the requirements of the occupied spaces. This adjustment ensures an ideal balance between indoor air quality and energy consumption.

Victory Lane Project Recap

The project resulted in a substantial improvement in operational efficiency, representing a 7% decrease in the building’s annual energy consumption and utility costs.

Retro-Commissioning

The figure below illustrates the year-over-year improvement to operational efficiency. This energy consumption data is weather normalized to account for variations the building’s heating and cooling loads and shows a consistent reduction in electricity consumption occurring throughout the first half of 2023.

Retro-Commissioning

It’s a three-way tie of winners in the retro-commissioning game: building owners, operators, and occupants. This project exemplifies the value of optimizing existing buildings for improved energy efficiency and occupant comfort.

Through the collaboration between ESD, now Stantec, property management, and the building engineering team, the 151 North Franklin study successfully identified energy conservation opportunities, resulting in substantial energy savings and cost reductions. This demonstrates the efficacy of retro-commissioning as a viable solution for enhancing the sustainability and performance of commercial buildings, ultimately benefiting both the environment, and building owners.

Matt Zweibruck shares his expertise in the demand-side energy services industry in support of the company’s mission to build communities and improve society through the built environment.

Contact ESD, now Stantec’s experts for more information on how we can help with energy efficiency and other carbon reduction planning.

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