BIM-VE-Based Optimization of Green Building Envelope from the Perspective of both Energy Saving and Life Cycle Cost

In the context of the increasingly severe energy crisis and global warming, green buildings and their energy-saving issues are being paid more attention in the world. Since envelope optimization can significantly reduce the energy consumption of green buildings, value engineering (VE) technology and building information modeling (BIM) technology are used to optimize the envelope of green buildings, which takes into account both energy saving and life cycle cost. The theoretical framework of optimization for green building envelope based on BIM-VE is proposed, including a BIM model for architecture, a life cycle cost analysis model, energy-saving analysis model, and a value analysis model. In the life-cycle cost model, a mathematical formula for the life-cycle cost is established, and BIM technology is used to generate a bill of quantity. In the energy-saving analysis model, a mathematical formula for energy saving is established, and BIM technology is used for the building energy simulation. In the scheme decision-making sub-model, VE technology integrating life cycle cost with energy saving is used to assess the envelope schemes and select the optimal one. A prefabricated project case is used to simulate and test the established methodology. The important results show that the 16 envelope schemes make the 16 corresponding designed buildings meet the green building evaluation standards, and the optimal envelope scheme is the “energy-saving and anti-theft door + exterior window 2+ floor 1+ exterior wall 1 + inner shear wall + inner partition wall 2 + planted roof” with the value 10.80 × 10−2 MW·h/ten thousand yuan. A significant finding is that the value generally rises with the increase of energy-saving rate while the life cycle cost is irregular with the increase of energy-saving rate. Compared with previous efforts in the literature, this study introduces VE technology into architectural design to further expand the current boundary of building energy-saving theory. The findings and suggestions will provide a valuable reference and guidance for the architectural design industry to optimize the envelope of green buildings from the perspective of both energy saving and life cycle cost.