Urbanization can negatively impact the natural environment, and dense urban layouts influence the urban wind patterns. These influences include the quality of outdoor and indoor environment quality. Hence, the urban environment and living quality are becoming significant issues in the domain of urban design. This study focuses on external flow patterns and ventilation performance in urban wind environments created by different building types (e.g., terrace, detached, courtyard building) and urban street layouts. In our previous investigation, the CFD (computational fluid dynamics) setups were verified by field data. Thus, this study procedure can be applied during the design stage with reasonable accuracy. This study therefore applies CFD simulation for parameter analysis. Three street layouts were analyzed and analyses were based on average wind-speed ratio (u/Ur) and external flow patterns. Change in the average wind-speed ratio is small when the street aspect ratio is small for all urban street layouts. In the first street canyon (upwind), variation in the average ratio depends on the reference wind speed. When the street aspect ratio increases (narrow streets), the correlation between the average wind-speed ratio and reference wind speed is weak. For the layout of detached, the correlation between the average wind-speed ratio and reference wind speed is also weak. Only wide streets in the layout of detached buildings markedly increase the average wind-speed ratio in the canyon. Due to the small area on the windward side of building, wind speed variation in the canyon is small and is only minimally influenced by the reference wind speed. For buildings with courtyards, variation in the average wind-speed ratio decreases as the street aspect ratio increases. The CFD calculation demonstrates that the wind environment in courtyards is generally stable, and only minimally influenced by the external wind environment.