Under the impact of aging and high housing prices in Taiwan, the demand for changes in residential space has increased due to the need for long-term use. Consequently, this research is based on support and infill separation system and two-stage construction by the open building theory. Hereafter, the concept of a barrier-free environment and universal design are combined as the theoretical basis for design operations. A residential unit is developed to adapt the variation mode of the aging process and provides a means of interaction between the housing （hardware） and the user’s living needs （software）. The process of this research is mainly divided into three phases: Phase 1: To collect the data from relevant literature and practical case, which included a combination of barrier-free environment and universal design concepts, as well as to understanding the evolution of domestic residential units. Phase 2: Explored the possible changes in the two-stage construction of the support and infill in the overall system of domestic collective residential from the perspective of open building theory, in order to comply with the changes in each phase of the lifecycle. Phase 3: Explored the post-change spatial combination through image simulation to provide a basis of reference for lifetime home design and practical construction, based on previous design results. The results of this study could be found as follows through the analysis and simulation phases: First, the commercialized residential units are suitable for users in healthy periods. However, these residential units are unable to change the space configuration to suit the requirements of users’ need, when the users are stepped into the obstacle period from the health period. Second, proposed the recommended values of the space size for each house type units in the obstacle period and bed-reclined period.