The expansion of the east wing represents the symbiosis of a 1927 building with contemporary exigencies. To uphold this institution’s international trauma centre reputation, it was necessary to expand. Here, through a rhythmic reproduction of the original window patterns, the natural light that soothes body and mind is captured via abundant fenestration for the well-being of patients and health care professionals alike. Respectful of the heritage character of Sacré-Coeur, the vertical alternation between solid walls and curtain walls also enables greater energy efficiency.