The current version of the sensor network was deployed in eight single-family buildings in Switzerland. The deployment started by the end of January 2017 and was ended in May 2017. Ideally, we would have started at the beginning of the heating season. One sensor kit was placed in each house. A sensor kit consisted of 18 sensor nodes, 5 router nodes, and 1 gateway. Just in these eight buildings, we have encountered a large variety of heating system setups: the energy source for heating, the energy source for domestic hot water, the metering infrastructure, the heat emission systems, and the heat storage. Sometimes we would only learn about the circumstances when being in the actual buildings.

The case study participants were all buildings owners, who were customers of building energy assessor. We cooperated with the assessor, who asked his customers if they were interested in participating in a case study. The assessor provided us with his assessment of the buildings, which included building plans. We used the information to propose the placement of the sensors. After arrival on the side, I would sit down with the case study participants and explain the reasons for the case study and the course of action. During this talk, I would also discuss a data privacy statement, which they had to sign. Then, the building owners would show me the building, and during this tour, I made suggestions about where to place the sensors. If the building owner agreed, I would put the sensor on the floor for later installation. If the building owner disagreed, we would find an alternative solution. After the house tour with the owner, I would install all sensors properly, clean up and check whether all sensors appeared online. By the end, I would again make a tour throughout the building with the owner, indicate the sensors and asked whether he/she was content with the installation. Then I would say good-bye. The whole deployment including introduction, house tours, questionnaire took on average 2.5 hours.

The oil flow meter for oil-based heating systems was installed by a third party after the initial sensor deployment. (Pro tip: measure the diameter of the oil line during the first visit, or you have to visit again). After the oil meters were installed, I would go back to the building for a check on all the sensors (check whether they still stick where I stuck them or whether they fell off). The sensors held up quite well. However, a few fell off (e.g., heat flux sensors or reed switches) but nothing major. The check of the sensor network took about one hour per building.