The project: Onni Group’s major gut-renovation of the 933,143-sf, 33-story office tower at 225 W Randolph St in Chicago, IL.

The goal: The building, which originally opened in 1966, required an extensive overhaul from various aspects. Onni Group’s plans for the building included the creation of new core and shell office spaces with a new bar and restaurant in the lobby and a three-level addition to the top of the building to house a spa, pickleball court, and lounge. The building also contains two subterranean levels of garage parking and back of house spaces.

Design approach: IMEG performed a full life cycle cost analysis prior to design in order to select cost-effective and efficient systems that would integrate well into the existing structure (with relatively low floor-to-floor heights) and maximize tenant space. Key systems and capacities included a new water cooled VRF system with 2500-tons of condenser water production and 36 million BTU of boilers. Additionally, IMEG’s designs included new electrical distribution throughout (replacing 4 existing service switchboards and distribution) and a new 600kW life safety generator. The building also received upgraded glazing throughout to assist in energy reduction.

Challenge: Working within an existing, operational structure. Solution: Close coordination with the owner (who is also the GC) and structural engineer.

Challenge: The building is landmarked, so exterior modifications were subject to scrutiny by the city. Solution: the project team worked together to obtain the city’s approval and move forward to complete the exterior modifications.

The outcome: The renovation and addition provide great efficiency, comfort, acoustics, and height to each tenant floor. The newly renovated facility is LEED Gold and WELL Certified.