Professor Tillmann Klein (09-05-1967 — † 17-06-2023) was lead instructor responsible for several online courses on circularity and sustainability in architecture and the build industry. He is sorely missed.

Tillmann Klein studied architecture at RWTH Aachen, Germany. He worked in several architecture offices, later focussing on the construction of metal and glass facades and glass roofs. Simultaneously he attended the Kunstakademie in Düsseldorf, Klasse Baukunst. He was a co-founder of the architecture office rheinflügel baukunst with a focus on art-related projects. In 2005, he was awarded the art prize of North Rhine-Westphalia for young artists.

From September 2005 until 2018 Klein headed the Facade Research Group at the TU Delft, Faculty of Architecture and the Built Environment, and from 2008 until 2016 he was director of the façade consulting office Imagine Envelope b.v. in The Hague. Tillmann Klein organised the international façade conference series ´The Future Envelope´ at TU Delft and was editor in chief of the scientific open access ´Journal of Façade Design and Engineering´. He also established the Circular Built Environment Hub – a cross-departmental, dedicated community teaching and conducting research on circularity.