Chicago’s Old Post Office building is getting some new windows—2,400 to be exact

After a decade of vacancy and decay, it’s difficult to fathom just how large Chicago’s Old Post Office really is. After all, the Art Deco structure isn’t particularly tall by Windy City standards—rising only 15 stories above the banks of the Chicago River. While an on-going effort to convert the hulking building into a whopping 2.5 million square feet of rentable Class A office space sounds like an impressive number, visualizing the sheer scope of the project can still be a tricky exercise in abstract thought.

However, thanks to a recent building permit, the true magnitude of the renovation can be more clearly grasped. According to the City of Chicago document, the Old Post Office building at 404 W. Harrison Street will be receiving no less than 2,404 replacement windows.

This mind-bogglingly massive window job is just one component of developer 601W Companies’ $500 million plan to reposition the behemoth structure straddling Chicago’s Eisenhower Expressway. Teaming up with architect Gensler, the New York firm is upgrading the old building’s roof, elevators, stairs, plumbing, and other mechanical systems. Plans also call for an overhaul of the PO’s grand lobby and the addition of a riverwalk plaza and three-acre rooftop fitness center.

601W hopes to lure large scale commercial users attracted to the building’s 18-foot ceilings and 250,000-square-foot open floor plans. With a total of 2.5 million square feet—and 2,400 new windows—on tap, Chicago’s Old Post Office is expected to be home to as many as 12,000 employees once work is completed and tenants are secured.

Gensler

• Renovation/alteration permit at 404 W. Harrison Street [Chicago Cityscape]
• Permits signal work on Chicago’s Old Main Post Office moving inside [Curbed Chicago]
• Another big permit issued for Chicago Main Post Office renovation [Curbed Chicago]