This paper presents the following contents in order to establish a design support tool for early design phase based on an optimization of indoor heat load of a building.1) An optimization program with design variables: building shape, thermal performance of building envelopes and opening size, was developed.2) The three optimization methods (SGA, ABC and FA) were studied in terms of their adaptability for the program.3) Detailed investigation was conducted on the program with FA in order to understand the characteristics of the method.