Rapid urbanization in emerging economies, like Vietnam, is commonly realized via the multiplication of stereotype projects consisting of high-rise apartment blocks, terraced, semi-detached and detached houses. For these types of dwellings, in the hot and humid Vietnamese climate, individual air conditioning systems are typically used. This requires a large share of the country energy resources. Until recently comfortable traditional housing has however been built without using such energy intensive cooling. This paper focuses on the energy consumption and thermal comfort in residential buildings if only natural ventilation is used, taking into account the urban environment. Via a parametric simulation several building types are optimized, looking at the urban layout, building orientation and size, window design and internal wind permeability. A two-step procedure is followed for the analysis. Firstly, a simplified model is used to analyse a large range of design alternatives and secondly, dynamic energy and thermal comfort simulations with EnergyPlus are made for a selected number of design options. Results reveal that the average life cycle cost of the optimal cases is 34% lower than the reference cases. The window sizes, building layouts and urban forms are crucial parameters to compensate with orientations at the early design stages. One optimization procedure was developed to make maximum use of passive design measures in large scale housing projects. Key words: EnergyPlus, GenOpt, Natural ventilation, Method for cost control, Parametric Wind pressure coefficient.