The manufacturing stage, transport stage and on-site construction stage of building materials consume large amount of energy. Based on the three stages, the calculation method for energy and exergy consumption was presented, and the concept of exergy-energy ratio was proposed to evaluate the sustainability of building energy use. A case of a research and development center located in Hunan was analyzed. The results have shown that the energy consumption of building envelope construction mainly comes from the manufacturing stage of building materials. Unit building area energy consumed by concrete and steel accounted respectively for about 44% and 41% of the total energy consumption of building materials production. Unit building area exergy consumed by concrete and steel accounted respectively for about 38% and 48% of the total exergy consumption of building materials production. From the perspective of exergy-energy ratio, the maximum value is steel, 0.92; and the minimum is cement, 0.59. The exergy-energy ratio of building envelope construction is 0.79. The results can provide reference for the research of energy consumption resulting from “uncompleted building”. The exergy assessment method presented can be applied to other similar buildings, and can provide reference for sustainable building construction.