A unit remodeling space optimization model, using GA, was proposed in this study. It is important to select the optimum of many alternative of design element at an early design phase of its influence on the other elements. Also, the problems in the process of design are as the selection problems of alternative to satisfy the building performance and the constraints related with a building. This study is on the method using GA by which Visual 6.0 C++ can find the optimal solution in wide range of selection intelligently. Specially, it is applied to the selective problem of the unit remodeling space between insulation performance and cost. And it find the optimal solution that satisfies this relationship. (1) The fitness function of the GA was drawn up considering cost of usable space. Parameter of 30 chromosomes population, 0.9 crossover probability, 0.01 mutation probability, 2,000 repetitions was applied (2) After applying GA, it was found that in case of Remodeling Space Optimization.