Ensuring our buildings are fit for the 21st century is a key industry challenge. The challenge is particularly vexing when dealing with existing building stock and having to decide between a sustainable retrofit within the scope of an existing building use case, or adapting the building for a different use case. A realistic scenario in this context requires students to advise a client on the relative merits and recommended option between sustainable retrofit or conversion. For example, a commercial office building in the Sydney CBD, approximately 25 years old, and a concrete framed, 17 storey high rise building with retail use on the ground and lower ground floors. The building is classified as a PCA Grade B office. There is 10% vacancy in the building and the owners are concerned that vacancy will increase without a building upgrade. Students research new technologies to improve building performance and sustainable retrofits, consider procurement and best practices in reducing the environmental impact of construction, and review social aspects of construction. Students then examine sustainability in leasehold and freehold property to produce a professional report on a best practice solution to the retrofit or conversion decision.