# Data-Driven Decision Support for Smart and Efficient Building Energy Retrofits: A Review
## 4 Data-Driven Approaches to Building Energy Retrofitting
### Data Sources  
Effective data collection is crucial for assessing the performance of energy retrofit interventions in buildings; several methods are employed to gather the necessary data for energy retrofits. Building Management Systems (BMSs): BMS integrates various building systems and sensors, collecting and managing data related to energy use, indoor environmental quality, and system performance. BMSs are central hubs for data collection, integrating various sensors and systems within a building. The author in [PERSON] et al. [28] used a dataset consisting of real-time monitored data from the Energy Management System (EMS) and Building Automation System (BAS) of the CalSTRS building to gather comprehensive performance data. This dataset includes energy use recorded at hourly intervals and HVAC operating conditions as well as environmental data captured at 15 min or 1 min intervals. The study demonstrated that such high-resolution data are crucial for identifying inefficiencies in energy use and optimizing building performance. For instance, detailed monitoring of the HVAC system revealed opportunities for operational improvements, such as better control strategies and adjustments to equipment settings, which directly informed retrofit decisions. Moreover, the use of real-time data helped overcome common data collection challenges, such as reliance on periodic or aggregated data that may obscure short-term inefficiencies. By leveraging detailed and continuous data, the study provided more accurate insights into building performance, allowing for targeted retrofitting measures. In the work of [PERSON] et al. [29], the authors used the automatic collection of real-time building energy consumption data gathered from the building management systems to develop an advanced retrofitting decision support tool that support step-by-step thinking for retrofitting design and hopefully enable a larger utilization rate for deep building retrofits. In the industry, solutions like Schneider Electric's EcoStruxure(tm) Building Operation further illustrate how BMS platforms integrate various building systems, providing critical data that support energy efficiency initiatives and informed decision-making for retrofits. Sensors and IoT Devices: Sensors are widely used in energy retrofits in buildings because of their ability to provide granular data on specific parameters crucial for optimizing energy use. Temperature sensors measure ambient temperatures across different zones, which is essential for evaluating the performance of heating and cooling systems and ensuring that temperature control is effectively managed after retrofits. Occupancy sensors detect the presence of individuals in a space and adjust lighting and HVAC systems accordingly, thereby enhancing energy efficiency by reducing energy consumption in unoccupied areas. In addition, power meters measure electrical consumption at various points within the building, providing detailed information on the energy usage of specific systems or equipment. This information is invaluable for identifying inefficiencies and opportunities for improvement, enabling more targeted and effective retrofit strategies, according to [PERSON] and [PERSON]. [26], [PERSON] et al. [11]. In the industry, companies like ReMoni offer advanced sensor solutions that provide the real-time monitoring of energy usage and equipment performance, further demon starting the critical role of sensors in optimizing building energy efficiency during and after retrofits. Energy Audits: Energy audits are systematic evaluations of a building's energy use. They involve a combination of visual inspections, data collection, and analysis to identify areas for improvement. Audits typically assess the performance of the building envelope, system efficiencies, and operational practices. The comprehensive nature of energy audits makes them a valuable tool for establishing baseline energy performance and developing targeted retrofit strategies.