The building sector is responsible for nearly 40% of global energy use and CO₂ emissions, creating an urgent need for sustainable thermal management strategies. This work reviews recent advances in thermal modeling, heat recovery systems, and renewable-integrated HVAC technologies aimed at enhancing building energy efficiency and supporting global decarbonization goals. High-fidelity modeling approaches—including Computational Fluid Dynamics (CFD), Finite Element Method (FEM), and co simulation platforms—enable accurate assessment of passive systems such as Trombe walls and PCM enhanced façades, as well as active solutions like geothermal-solar hybrid heat pumps, variable refrigerant flow (VRF) systems, and thermally driven chillers. Parallel developments in heat recovery devices, including energy recovery ventilators (ERVs), drain-water heat recovery (DWHR) units, and flue gas economizers, demonstrate potential seasonal energy savings of 30–60% when integrated into HVAC systems. The review highlights the complementary role of IoT-enabled controls, exergy-based evaluations, and life-cycle assessments in translating modeled potential into real-world performance. Despite rapid progress, research gaps remain in long-term field validation, integration of dynamic occupancy behavior, and techno-economic feasibility at district scales. Addressing these challenges is essential for advancing next-generation thermal systems that deliver scalable, resilient, and net-zero building solutions.