The "DTH zero-energy house" by Prof. Vagn Korsgaard (Kopenhagen, 1973) was also a Passive House. At the Technical University of Denmark, simulations were systematically carried out, designs were optismised and the first zero-energy house was built. The building was later used as a guest house for the university. However, the active solar technology was not renewed after it became defective. As a result, the "zero-energy house" objective was set aside in favour of the "low-energy house".
Experiences from this project were directly incorporated into Passive House research from the very beginning.