Solar thermal venetian blinds (STVB) pursue the goal of reducing the primary energy demand of buildings with highly transparent façades during operation. They can provide solar control and daylighting functions and at the same time function as a solar thermal collector. A technical overview of STVB based on a design parameter space, which can be used as guideline for the design of STVB, is presented. It is then applied to develop a first actual-size test sample of STVB. The design principle, based on heat pipes and a switchable thermal coupling for heat transfer between the slats and a header tube, allows the STVB to be tiltable and retractable. The key characteristics of the built STVB test sample are: (1) integrated in a double skin façade element; (2) conventional absorber sheet with diagonally mounted heat pipe; (3) switchable thermal coupling with mechanism using springs and solenoids; (4) a multi-port header tube. Outdoor measurements have been carried out and are discussed, demonstrating the technical feasibility of the concept. In the end, design choices for architects and planners for the STVB system and possible installation processes are presented, and recommendations for further developments are assessed.