The most significant element affecting the architectural environment in the tropical and subtropical region is solar energy, which influences either its inside or outside the buildings. External louvers can be utilized to block the solar radiation before it reaches the indoor environment, hence, more effective than internal louvers system. On the other hand, external louvers will reduce the daylighting intensity, wind velocity as well as the air change rate inside the buildings. This study discusses the impacts of several different prototypes of external louvers in a classroom in Taipei via the use of ECOTECT/RADIANCE trial version package for daylighting and PHOENICS Computation Fluid Dynamics software for natural ventilation simulations. The combination of these two elements may create a better louver type, even if it is not so easy to create the optimal louvers on both daylighting and ventilation. Finally, summarizes the results of this work and indicates future work required to figure out the best louver geometry and the influences on louvers for indoor air quality.