Cyclone Case Study: 10 South LaSalle
Published by Ian O’Connor
10 South LaSalle is a 502 ft tall skyscraper in the LaSalle Street financial district of Chicago, Illinois. It was completed in 1989 and, at 37 floors, it is tied with One Superior Place for the 87th tallest building in the city. Located at the southwest corner of Madison and LaSalle streets, the building is owned by The Feil Organization and was designed by Moriyama & Toshiba Architects, making it the tallest building in Chicago designed by a Canadian architecture firm.
The 10 South LaSalle Management team sought retro-commissioning services through Cyclone Energy Group and the ComEd Efficiency Program. The project’s target energy cost savings were $30,000 per year, or roughly 4% of total building energy consumption. Under the ComEd RCx program, property owners receive a free retro-commissioning study to identify low and no cost energy efficiency measures. In addition, the property owner can have some, if not all the implementation cost covered by an incentive based on verified savings.
The building has water-cooled chillers and electric resistance heat at the terminal units. The airside systems are constant volume, cooling-only AHUs. The building automation system is over 15 years old and has limited visibility into many systems due to the presence of many pneumatic systems still present in the building. For example, the terminal unit heaters are locally controlled by individual thermostats within each zone and were not addressable within the scope of the RCx project. Despite these limitations and constraints, Cyclone Energy Group performed a comprehensive review of the equipment and building automation system to identify opportunities for improvement.
Eight ECMs were identified in the investigation phase.
- Condenser water return reset
- Chilled water temperature reset
- Exhaust fan scheduling
- AHU scheduling
- Efficient filter installation
- Optimize mixed air temperature control
- Economizer setpoint
- Minimum outside air reduction
In total, these ECMs were projected to save the building roughly 470,000 kWh per year, exceeding the 375,000 kWh target by a healthy margin.
Several ECMs were removed due to latent conditions. The building staff decided to plan a chiller replacement, so ECM 1 and 2 were removed since these would be addressed within that upcoming project. ECM 4 was removed because the AHU of concern must run 24/7, and ECM 7 was merged with ECM 8.
Four ECMs were chosen for implementation.
- Exhaust fan scheduling
- Efficient filter installation
- Optimize mixed air temperature control
- Minimum outside air reduction
As typical with Cyclone’s experience, most of the measures are related to improving equipment scheduling and tuning pressure and temperature set points with care taken to not disrupt occupant comfort. One measure alone was found to have the potential of saving 7% of total building energy use.
Despite the reduction in scope, the building achieved energy savings of over 860,000 kWh per year, largely due to the expansion of ECM 6 (Optimize mixed air temperature control) from one constant volume air handler, AHU-10-INT, to all 70 of them.
AHU-10-INT was identified as having a mixed air temperature setpoint of 58°F year-round. By resetting the mixed air temperature setpoint up to 65 degrees when the outside air is 35 degrees and below, the air handler can reduce the need for reheat at its downstream terminal units.
Upon implementation, it was discovered that all the AHUs had a fixed mixed air temperature setpoint of 58°F and significant reheat energy savings could be captured by applying the same logic to all the AHUs. This is a simple way to reduce energy consumption in constant volume, variable temperature AHUs. The building achieved energy savings of over $68,000 per year, more than twice the target savings. The outsized energy savings of the project is largely due to the mixed air temperature optimization measure. By resetting the mixed air temperature set point up to 65°F when the outside air is 35°F and below, the air handler can reduce the need for reheating at downstream terminal units.
During the verification phase of this project, Cyclone Energy Group confirmed there was no impact on occupant comfort.
Overall, the project achieved 860,000 kWh per year of savings, nearly 10% of the total building energy consumption. Due to the substantial energy savings, we are tracking and weather-normalizing the utility bills to compare with historical consumption to further verify the savings. So far, the weather-normalized utility savings for the first quarter of 2023 exceed 250,000 kWh per year.
