In this study, a medium-sized residential building is analyzed when an internal combustion engine-based combined heating and power (CHP) system is applied. The multi-family building with a floor heating system is selected to represent typical Korean residential situation. Simulation models are developed for the building, prime mover, thermal storage system, and cooling and heating systems. The validated CHP model is integrated to the building, and it is operated with a thermal load following method. The CHP applied residential building model is compared to the baseline model with a grid power and a gas fired boiler system, in terms of energy, environment, and economics. When the CHP system is applied to the residential building in South Korea, total primary energy consumption is decreased by 18.4%, CO2 emissions by 11.8%, and operation cost by 9.6%, respectively. Based on the facility and operating cost, the payback year is calculated as 10.2. In addition, the building performance is further discussed in terms of weather conditions, utility fee change and energy utilization method. (C) 2019 Elsevier B.V. All rights reserved.