The Effretikon-Illnau housing cooperative owns several properties. One of them is the Illnau housing development, which also includes the Chrummenacher 9 retirement community. After 30 years of use, the oil heating for heating and hot water generation in the building was replaced by an air/water heat pump. The challenge was to carry out the conversion in the existing building during ongoing operations.

TBF conducted a feasibility study (SIA phase 21) of various heating systems and planned, projected and installed the complete system from (SIA phases 21-53).