Thermal comfort and occupant thermal satisfaction are critical aspects in the indoor environment quality assessment and have received considerable attention by designers and building occupants. Improper indoor temperature not only decreases the level of occupant thermal satisfaction, but also has serious health related consequences. Despite the importance of occupant thermal satisfaction that has been vastly emphasized, studies incorporating occupants' satisfaction during the design process are very limited. Therefore, this study aims to develop a multi-objective design optimization model to minimize life cycle cost and life cycle emission, and maximize occupant satisfaction level in a typical commercial building. To solve the multi-objective optimization problem, a Harmony Search based algorithm is developed and employed. Moreover, to identify the level of design thermal satisfaction, a novel utility theory based thermal comfort index is defined and calculated. A small office building is selected as a case study to analyze four different designs which are identified as optimum solutions. To determine the optimum designs, the satisfaction level of all the design combinations having cost and emissions similar to previously distinguished optimum solutions are compared and best designs are identified. (C) 2017 Elsevier Ltd. All rights reserved.