Final answer:
Louis Sullivan's Wainwright Building differs from International Style buildings due to its use of ornamental elements and a transitional architectural approach that is less austere than the latter's emphasis on volume, industrial materials, and rejection of decoration.
Step-by-step explanation:
What distinguishes Louis Sullivan's Wainwright Building from International Style buildings is primarily the approach to design and ornamentation. Louis Sullivan, who is often quoted for the axiom "Form follows function," was a proponent of architectural design that still incorporated ornamental elements despite its functional-driven form. This concept was a bridge between traditional architectural styles and the emerging modernist functionality. In contrast, the International Style, as defined by the Getty Research Institute, involves buildings that emphasize volume over mass, utilize industrial materials, and strongly reject ornament and color in favor of repetitive modular forms and flat surfaces, often with large areas of glass.
While the Wainwright Building does exhibit a strong alignment with the functionality of a commercial office building, it is also known for its ornate terra cotta friezes and a distinct architectural expression that represented a transition from older styles to modernism, marking it as a precursor to what would become the less adorned International Style.