The paper tackles the integration of engineering performance simulations in the conceptual phase of architectural design, with specific focus on parametric design processes. A general framework is exemplified, in which the use of performance simulations and the learning process of the designer are discussed in relation to the parameterization process. A specific case study is presented more in details regarding the design of an atrium for the reuse of an existing building in Shenyang-China. Performance simulations concerning the thermal comfort in the atrium are presented and discussed in relation to the general framework.