The digitalization trend in buildings is accelerated with advancements in information and communication technologies (ICT). These technologies enable many opportunities in buildings to achieve resource and energy efficiency based on either monitoring or advanced control of buildings. The ICT solutions’ overall impacts on the environment are often presumed positive without an assessment based on life cycle thinking. The research on ICT solutions in buildings is mainly related to occupancy, energy, and indoor environmental monitoring with the focus on technical performance and potential benefits while the environmental impacts are often overlooked. This paper analyses two case study buildings in Sweden with building monitoring systems (BMS) based on life cycle assessment (LCA) methodology. The two cases were chosen to represent a range between simple and more sophisticated. The results show that sensors and wires contribute significantly to several impact categories and the impacts of electronics used for data acquisition are also important. The climate impact of the production phase is significantly higher than the use and waste management. Depending on the energy mix, the minimum required energy saving to offset the climate impacts of the BMSs are 5% (standard BMS) and 24% (extensive BMS). This is comparable to the energy savings that often are assumed when building monitoring systems are introduced. Thus, the direct impacts of the enabling technologies for digitalization might be significant and it is crucial to employ a life cycle perspective when assessing the environmental benefits of digital solutions in buildings.