The increasing global energy consumption, driven by industrialization, technological advancements, and population growth, has raised some serious environmental concerns, including the depletion of energy resources, global warming, and climate change. The building sector is regarded as a primary contributor to energy consumption and greenhouse gas emissions, accounting for around 36% and 39%, respectively, of overall energy usage. This study performs a bibliometric literature review to know and understand the trends and role of the Internet of Things (IoT) in HVAC system optimization. A systematic search is performed in the Scopus database to find 1,156 relevant articles published between 1984 and 2024. A bibliometric analysis is conducted using the VOS viewer software to provide a bibliographic view of the scientific landscape of the research area, with a particular focus on the visualization of keyword co-occurrence, annual publication trend, and publication platform review. Findings reveal that the emerging research trends, key technological advancements, such as machine learning integration, smart sensors, and adaptive control mechanisms, are found to have dramatically enhanced energy savings and system efficiency.