Energy consumption during use is the focus of insulation envelope design, but the environmental impact of other stages in the entire life cycle of building envelopes should be of equal concern. In this paper, a model has been developed based on the life-cycle environmental assessment for calculating the environmental impacts of building envelopes. The model proposed will be useful to evaluate the environmental performance of various envelopes to optimize the design of energy-saving envelopes. Consequently, lots of experiments are conducted for environmental impact assessment and analysis for external windows and filler walls with energy-savings in heating areas of China. Four conclusions can be drawn from the analysis. (1) K of building envelope is the design parameter of the greatest impact on environmental performance and has a critical value, which is the value that has the smallest environmental impact over the entire life cycle. (2) The importance of the environmental impact of the building envelope during the life cycle stages is as follows: usage > production > transportation > disposal > construction. The construction process of the thermal insulation wall could be negligible. (3) The choice of regional building materials should consider the distance of transportation, which may be the key factor determining its life cycle environmental performance. (4) Aerated concrete EPS walls and wooden windows are the first choices for envelope construction from the environmental impact throughout the life cycle.