## 3 Methodology: Requirements Analysis, Selection of Buildings, and Technologies
### Deriving Technologies and Instrumentation Variants
#### 3.3.1 Requirements  
In the context of the general requirements discussed in the previous section, the following are aspects that were considered in the selection of devices. Usability for Science  
The measurement of several physical quantities is required for the scientific/research goals of the project. The overall goal is to improve the energy efficiency of the buildings, while maintaining or even increasing current comfort levels. To improve heating efficiency, the ability to sense the temperature of the thermal zones, as well as to automatically regulate the heating system, is required. Temperature sensors and radiator status sensors and actuators are, therefore, necessary. However, energy savings and user comfort often constitute conflicting goals. In line with standard considerations in BAS for non-residential buildings, it is important in this research project that the productivity of occupants is not negatively affected by energy-saving measures, as research shows that poor _indoor air quality_ (IAQ) leads to decreased productivity [63, 64]. Consequently, it is necessary that IAQ parameters are monitored in the various controlled spaces, so that energy-saving measures and metrics can be counterbalanced by acceptable IAQ conditions. On the electrical energy side, luminosity sensors and electronic light switches are necessary for the efficient control of ambient lighting. Furthermore, according to research, plug and process loads take up to 47% of the energy consumption of commercial buildings in the USA [65], and up to 28% in the UK [66]. As a result, controllable power meters are beneficial to address this scenario. Furthermore, user engagement is one of the key topics at LLEC, with a sub-topic being the evaluation of the energy performance of building occupants. It is also desirable to have motion sensors and occupancy detection devices to support this goal. In addition to the quantities of interest themselves, the characteristics of the measurements are also important. For the purposes outlined above, the numerical resolution, time resolution, correctness, and the time constant of the devices need to be considered. Numerical resolution refers to the smallest change in the physical quantity that can be reported by the sensor. Time resolution refers the frequency of measurements that can be obtained from the sensor. The correctness of a measurement indicates the maximum deviation between the reported measurement and the real value. The time constant is especially important for tasks which close a control loop. From our experience, when searching for device models, we can report that, in many cases, time constants are only given for the pure sensor elements, but not for the total sensor device as delivered. Acceptance by Users and Infrastructure Managers  
In order to ensure user acceptance, the prevailing culture and social predispositions of the users need to be considered. For example, in Germany, privacy is taken more seriously than in many other societies, and supporting structures such as the Works Council and Data Protection Officers that serve to protect employees from infringements are more vibrant than in most other European countries [67, 68, 69, 70]. Consequently, the installation of \"intrusive\" devices such as occupancy-detection devices is limited, with the goal of instrumentingwith a set of devices that enables the achievement of scientific goals. For calibration and validation purposes, it is possible that a narrow area is earmarked for more detailed instrumentation. The handling of privacy-related topics within the scope of our project is briefly described in Section 3.4. Additionally, it is important to consider the requirements and expertise of the infrastructure manager. All necessary considerations were coordinated with the aforementioned stakeholders. Device and Installation Costs  
An overarching consideration for selecting devices and technologies is cost, which can be expressed in three categories.