Journal of the Korean Solar Energy Society 한국태양에너지학회 논문집 ISSN:1598-6411(Print) 2508-3562(Online)

The building energy efficiency grade of old buildings in Korea is rated according to criteria of building energy performance calculated by the ECO2 energy simulation program. To evaluate this performance, ECO2 input data are required, which influence both the intermediate decision process and final calculation results. However, the required input data collection of old buildings for ECO2 simulation is not as simple as expected, and is more difficult than that for new buildings because of many unrecorded changes and updates after the original construction. In these aspects, certification assessment documents for old public buildings are not suitable for preparing input data for ECO2 and usually do not reflect the actual status and condition of buildings from either passive or active perspectives. Therefore, in this study, an ECO2 building energy simulation was performed for 41 old public buildings to examine how input data differences from on-site audits can induce differences in both the simulation process and results. The error range of the primary energy consumption for grades extended from 0 to 231.9 kWh/m²․yr, depending on whether on-site audit results are considered or not. Because of the long operation period of old public buildings, the initial design plan and current operation status have changed significantly, and our suggestion is that the confirmation step for collecting input data for old public buildings must be a prerequisite and an essential aspect for on-site investigation based on ECO2 simulation.