This paper presents an immersive gesture-recognition-based system to visualize the indoor thermal environment using Computational Fluid Dynamics (CFD). To enable efficient visualization of CFD in actual space, an Augmented Reality system was integrated with a CFD simulation engine. To facilitate efficient data manipulation of the simulated postprocessed CFD data and to increase user control of the immersive environment, an intuitive method of Human-Computer Interaction (HCI) has been incorporated using gesture and speech recognition. While gesture recognition aids in transforming hand postures into command functions through forward kinematics and computation of hand segment positions and their joint angles, speech recognition allows better control of the data manipulation. This enabled real-time interactions between the users and simulated CFD results in actual space.