Consideration on Carbon Emission of Existing Buildings in the Stage of Ultra-Low Energy Consumption Reconstruction

In China’s construction market, most existing buildings have high energy consumption and significant carbon emissions. This paper selects an office building in hot summer and cold winter areas for energy-saving transformation from high energy consumption to an ultra-low energy consumption building. By calculating carbon emissions in the transformation process stage by Yike Efootprint software, the building life cycle model is divided into an envelope Air tightness system, fresh air system, energy system, and door and window system. The five primary methods are described, energy input, energy consumption, pollutant output, process boundary, quantity used, upstream process traceability, sensitivity analysis. The materials and data are collected, analyzed, and calculated. The CLCD database is mainly used as the database, and some data are obtained from Ecoinvent. The CUT-OFF principle shall be used to reserve the materials with a significant weight proportion and high importance, and the materials with a weight less than 1% or with low significance and low material consumption shall be ignored. So we can get the critical influencing factors of carbon emissions in the transformation stage. By analyzing the influencing factors, we can provide some perfect suggestions for the energy-saving reconstruction of buildings. This paper uses LCA for modeling, calculation and analysis, data quality evaluation, and result output. So as to calculate the carbon emissions and effective recovery period of energy consumption from an ultra-low energy consumption building to a zero energy consumption building, it is proved that the carbon emissions in the transformation process can be recovered quickly through the energy-saving transformation of ultra-low energy consumption buildings. Ultra-low energy consumption buildings and zero energy consumption buildings will play a significant role in the development of China’s construction industry. It also provides more theoretical, and data support for developing zero-energy consumption buildings in China.