This study suggest a selection method for exterior glass with regard to energy efficiency, $CO_2$ emissions, and economics. First, it set up a hierarchy of factors for the selection of exterior glass and analyze their importance. As a result of the importance analysis, insulation is the highest importance factor, followed in order by economic and technical state, lighting, view, and others. Second, exterior glasses were classified for application in apartment buildings and office buildings based on the importance of selection factors, and then some types of exterior glass were selected for energy efficiency analysis. Third, this study analyzed energy efficiency, $CO_2$ emissions, and LCC(life cycle cost) after the selected glasses had been applied to actual office and apartment buildings. In cases in which two types of glass were applied to office buildings, the break-even points were 4 years and 14 years respectively, while the economic profits over 40 years were 2,536,332,214 won and 146,972,379 won. In cases where two types of glass were applied to apartment buildings, the break-even point was 1 year, and the economic profits over 40 years were 1,416,321,266 won and 130,760,294,093 won.