The insulation performance of a building is one of the most fundamental factors in reducing its energy use. The insulation of the building envelope is the main factor that directly affects the cooling and heating loads, which is responsible for the largest portion of the building’s energy consumption. Recently, in South Korea, building insulation materials such as PIR and PF, which have not only fire resistance but also high insulation performance, are becoming mainstream in the industry as fire safety standards have been strengthened. However, there are concerns about the long-term change of high-performance insulation materials. In particular, in contrast with existing plastic insulation materials such as EPS and XPS, the evaluation of the reliability of the long-term change of insulation materials with a high closed-cell rate is becoming an issue. This is because, unlike the existing EPS and XPS, there are insufficient international standard test methods for evaluating the long-term thermal performance of composite insulation materials such as polyurethane and phenol. They are combined with layers of other types of thermal insulation and/or one or both of the surfaces are covered with coatings, facings, membranes or other surface skins, all serving some functional purpose depending on the product application. In this study, the long-term change of building insulation materials was tested and analyzed based on the standard of the accelerated aging test. Four types of building insulation materials were used in the experiment: EPS, XPS, PF and PIR. The accelerated aging tests were conducted based on ISO 11561 and BS EN 13166 standards (accelerated laboratory test methods). The results of the accelerated aging tests for the materials were analyzed and the thermal resistance of the insulation materials was also compared. From the test results according to the slicing test method specified in the ISO 11561, the thermal resistance of EPS, XPS, PF, and PIR with long-term changes decreased by 2.4%, 8.5%, 16.4%, and 18.0%, respectively, compared to the initial thermal resistance. From the test results according to the 70 °C heat acceleration test method specified in the EN 13166, the thermal resistance decreased by 2.0% for EPS, 6.7% for XPS, 8.7% for PF and 13.6% for PIR, compared to their respective initial thermal resistance values. The EPS showed highly similar thermal resistance changes for the two different test methods. It was found that there was no effect from the slicing of the insulation material, and the accelerated aging test showed minimal changes in thermal resistance. In contrast, the other insulation materials exhibited different thermal resistance changes depending on the test method, with each material showing a thermal resistance change of 8.8% to 15.9% when subjected to the accelerated aging test.
