Improvement of thermal insulation performance of precast concrete curtain walls for apartment buildings

The increasing demand for off-site construction (OSC), in which buildings are constructed with factory-manufactured precast concrete (PC) members, reflects the need to improve construction productivity. The purpose of this study was to present an effective insulation plan for PC curtain wall-floor joints of apartment buildings with rahmen structure and PC curtain walls. For the existing case of the PC curtain wall-floor joint applied to a recently constructed PC apartment building, the insulation performance was evaluated through a three-dimensional steady-state heat transfer simulation. In addition, suggestions for improvements were made, and the insulation performance of alternative cases was evaluated. The evaluation results were subsequently verified through mock-up tests. As a result, it was found that the existing case needed to reduce thermal bridges caused by curtain wall corbels and fastening units. In the first alternative case, Alt. 1, the height of the insulation installed for the upper curtain wall was increased by moving the curtain wall corbel position downward. In addition, the upper fastening unit was installed where the curtain wall corbel was cut, and then sufficiently covered by adjacent materials. In another alternative case, Alt. 3, the thickest insulation between the curtain wall and the girder was used in addition to the conditions of Alt. 1. For Alt. 1 and Alt. 3, the effective U-factor decreased by 23.5 % and 32.4 %, respectively, compared to the existing case. Additionally, the thickness of the insulation between the curtain wall and the girder had a larger effect on the insulation performance than the thickness of the insulation surrounding the girder. Therefore, it was important to insulate as thick as possible between the curtain wall and the girder.