Old buildings over 20 years after completion account for 58.2% of all buildings in Korea, and buildings with weak insulation levels built 30 years ago have a significant impact on energy consumption in the building sector. Therefore, it is very important to improve the performance of existing buildings. The target of existing building reduction according to the implementation plan of the greenhouse gas reduction roadmap is higher than that of new buildings. In addition, green remodeling of old public buildings is currently being implemented in accordance with the mandatory zero-energy construction policy. ECO2 based on ISO 13790 and DIN V 18599 is officially used as a program to evaluate building energy efficiency ratings and energy independence rates in Korea. However, controversy has been raised over the accuracy of ECO2 because it cannot analyze the cross-use of cooling and heating energy generated in the intermediate stage and the amount of energy used at a specific point in time. In addition, previous studies found that the results of static analysis program showed higher energy performance than the results of dynamic analysis program. Therefore, this study attempted to analyze and compare the energy performance of green-remodeled public buildings based on both static analysis method using ECO2 program and dynamic analysis method using DesignBuiider program.
In this study, ECO2 and DesignBuilder programs were used to analyze and compare results of the primary energy consumption (heating, cooling, hot water, lighting, and ventilation) per year for a green-remodeled small public building. Results proved that the application of the green remodeling elements reduced the primary energy consumption per unit area the most, especially for heating energy. In addition, the change in the building energy efficiency grade through green remodeling improved by two stages from grade 1 to grade 1++ in the case of the ECO2 program, and improved by one stage from grade 1+ to grade 1++ for the DesignBuilder program. Overall, ECO2 program results were larger than that of DesignBuilder. Major differences occurred in heating energy calculation attributed to wind speed data, which is the difference in weather data items.