The Administration Building in Hasselager, as mentioned, is an excellent example of his work from the 1960s and 1970s. The building is characteristic of the era, where functionality and rationalism were dominant in commercial architecture. Its simple, monolithic form that simultaneously signals modernism is a key part of Blach Petersen’s signature style. Blach Petersen was often focused on how architecture could serve both practical and aesthetic purposes, and his buildings have a clean, clear expression that considers both functional and human needs.

His work strikes a balance between the technically modern and the human, which can be seen in many of the buildings he designed in Aarhus and beyond. One of his most well-known buildings is the Aarhus City Hall, which he co-designed with architect Erik Møller. It is one of the most prominent examples of functionalism and modernism in Danish architecture.Blach Petersen is often described as an architect who not only thought about aesthetics but also about how people would experience and use space. His work has left a lasting mark on the cityscape of Aarhus, and his buildings are recognized for their timeless design.