The Effects of the Frame Ratio and Glass on the Thermal Performance of a Curtain Wall System

Abstract

The curtain wall system is widely used in high-rise buildings because of its many advantages. With the increasing demands for building energy efficiency, thermal performance has become an important consideration in developing curtain wall systems. Even though the relative impact of the edge effect becomes more important as the thermal performance of glazing and the frame increases, the percentages of the frame out of the total curtain wall area have not been considered in evaluating its thermal transmittance. The purpose of this paper is to evaluate the effect of the frame ratio on the thermal transmittance of the curtain wall system. The state of the curtain wall frame ratio is analyzed by investigating recently constructed office buildings. Eight cases of different frame ratios and three types of glazing U-values are selected, and the total thermal transmittance of the curtain wall (Ucw) for each case was calculated by using TRISCO 12.0W. This study found that when the higher frame ratio is applied to the curtain wall system, the thermal transmittance of curtain wall is higher. Furthermore, the frame ratio has greater effect on the thermal transmittance of curtain wall when high performance glazing is applied to the curtain wall system. It is recommended that the certificates of a curtain wall system should show the frame ratio that was applied during testing or the accurate Ucw value considering actual frame ratio should be submitted for more reasonable building energy simulation.