<p> Introduction:</p><p> Spatial porosity is one of the essential concepts of passive design to respond to high temperature and humid climate in some regions of Southeast Asia where urbanization is rapidly expanding. Spatial openness, using airy space with large windows and voids, is a popular method for daylighting and natural ventilation in passive design.</p><p> On the other hand, it is a challenge to intake natural wind and light into the indoor space while avoiding intense sunshine and heat in a dense residential area, like Ho Chi Minh City in Vietnam. Moreover, these urban areas are sprawling with many medium height "tube houses" with narrow frontage and long depth standing close together. This characteristic for this location delimits the design direction, such as building size and window's arrangement. Thus, it is assumed that various brightness and wind distribution occur in the living space due to conflicts between the requirements of spaces and the environment. Hence, this paper aims to clarify spatial composition, wind environment and light environment of in-space in living space in contemporary houses in Ho Chi Minh City.</p><p> </p><p> Methods:</p><p> Firstly, spatial composition of in-space in living space is examined by investigating location characteristics, position of in ·space in relation to window and ground and properties of window. Then, the openness patterns of living space by window and the arrangement patterns of in-apace by distances to window and to ground are clarified.</p><p> Secondly, relationships between the composition of the living apace and the wind environment are examined. The wind velocity of each in-space is calculated by CFD simulation (STREAM ver. 13) and the combinational characteristics with the openness patterns are investigated. Furthermore, relationships between the composition of the living space and the light environment are examined. The illuminance of each in-apace is calculated by the daylighting simulation (VELUX Daylight Visualizer), and the combinational characteristics with the openness pattern of living space are investigated.</p><p> Thirdly, based on all these results, composite characteristics of spatial composition, wind and light environment are examined according to the combinations of the in·space pattern of arrangement and environment for each living spaces. Then, three different groups for the intentionality towards environmental design on wind and light are clarified.</p><p> </p><p> Results:</p><p> 1) Majorities of the openness patterns of living space are the high and the low openness for both light and wind. The arrangements of in-space tend to be close to the window and the ground. Furthermore, many in-spaces are allocated near the void and the skylight where much light and wind are easily reach inside.</p><p> 2) Wind velocity in in-space tends to be weak in living spaces which are the wind-window type and the light-window type. Illuminance in in-space indicates tendencies for the openness patterns that are more bright in the porous type and less bright in the less porous type.</p><p> 3) Composite characteristics of spatial composition, wind and light environment for each living spaces shows the light group is the majority and these living spaces tend to have various in-space's environments according to differences of their position. In the wind and light group, the arrangement patterns of in-space tend to be varied. These diversities could be considered as a specificity for living spaces and their indoor environments in the tropical climate which intends to be opened to the outdoor environment and to create an uneven quality of indoor environment.</p>