Indoor airflow and thermal environment always vary due to change of solar heat and outdoor temperatUre etc . Unsteady CFD simulation can predict such condition but it needs huge computational toad to satisfy CFL condition and to get stable results . Semi Lagrangian method can reduce the load which is applied in the fields of rnetrology and computer graphics . In this paper , CIP ( Constrained Interpolation Profile ) method which is one of semi Lagrangian method is dlscussed with several case studies .