One Illinois Center vs Promontory Apartments

Comparing the One Illinois Center and the Promontory Apartments is particularly interesting because they share the same skyline in Chicago, IL, and were both designed by Mies van der Rohe. However, they were completed more than 21 years apart.

This offers a unique perspective on how the architect's style and the city's architecture evolved over time.

The One Illinois Center is clearly the larger tower of the two, both in terms of height and number of floors. It rises to 361ft (110m) with 30 floors above ground, while the Promontory Apartments reaches 218ft (66.5m) with 22 floors above ground.

Of course, each project may have faced different briefs or regulatory constraints, which we don't really know about and could also explain the outcome.

Both the One Illinois Center and the Promontory Apartments were designed in line with the aesthetic conventions of the International Style style.

At the time, this style was at the height of its popularity. So Mies van der Rohe followed what was in many ways expected at the time, producing designs that fit comfortably within contemporary architectural norms rather, than breaking with convention.

The One Illinois Center is primarily commercial, while the Promontory Apartments is primarily residential.

The Promontory Apartments offers 122 residential units.

The One Illinois Center also provides 866 parking spaces.

Both towers share the same structural solution, a Frame system.

A frame structure uses a grid of columns and beams to carry the building's loads. This frees the walls from structural duties, allowing for flexible floor plans and larger windows.

However, when it comes to the facade, both buildings use different approaches. The One Illinois Center uses a Curtain Wall facade, while the Promontory Apartments uses a Window Wall facade.

A Curtain Wall facade like the one seen in the One Illinois Center uses a lightweight glass curtain wall hung from the structure, while a window-wall facade like the one seen in the Promontory Apartments uses panels fitted between floor slabs, leaving slab edges visible.