Construction projects are dynamic environments which are hard to monitor in real time conditions. Thus, traditional practices for productivity estimation, such as historical data analysis, do not provide enough information for decision making. This project proposes a new methodology to instrument and collect data in construction sites using embedded systems and IoT technologies. This solution is efficient in terms of energy, range, costs, and security of the data. In particular, it deals with one of the main challenges of implementing a Real Time Location System (RTLS). That is, we use an indoor technology and adapt it to the unfavorable conditions of constructions sites. The designed network is implemented in three different type of construction projects. Results show that our methodology can be used to determine the level of productivity of personnel in site and to record, analyze and rank their performance in different types of construction activities. This allows decision makers to promptly present alternatives to improve productivity, thus, achieving a positive impact in the fulfillment of the scope, schedule, budget, and quality of the projects.