Glass is always an important building material, especially in modern era in which the amount of high building has been significantly increased for several decades. However, the use of single-glazed windows has been generating the rise of building energy consumption. Thus, double-glazed window or insulated glazing was invented to minimize heating and cooling loads of building which is a major consumer of energy. This product has been commonly used in cold, hot and arid climate for several decades. This study discusses the effects of double-glazed windows on building’s energy efficiency and their effects on different window to wall ratio in hot humid climate. Five insulated glasses include clear glass; tinted glass; clear reflective glass; low emissivity (low-e) glass and low-e spectral selective glass are examined by DesignBuilder software in a hypothetical building in Taipei to choose appropriate glass units for building in term of reducing energy consumption while changing the window to wall ratio. Afterwards, building energy analysis will be assessed in each double-glazed window unit to investigate the energy efficiency of each one. Subsequently, these assessments will be used to determine energy efficiency of double-glazed units in an exist building located in Taipei.