Comparative life cycle assessment of a reinforced concrete residential building with equivalent cross laminated timber alternatives in China

With the development of mass timber, cross laminated timber (CLT) has gradually become a sustainable alternative to conventional building materials to alleviate the increasing energy consumption and carbon emissions by the building sector. This study aims to explore the life cycle greenhouse gas emissions (LCGHGE) and life cycle primary energy (LCPE) of three high-rise residential buildings in the cold region of China through a life cycle assessment approach. The three buildings are conventional reinforced concrete (RC), CLT and hybrid CLT buildings. The results show that CLT and hybrid CLT buildings produce 15.00% and 10.77% lower LCGHGE, respectively, compared to the RC building within a 50-year service life. A clear difference in greenhouse gas (GHG) emissions and primary energy (PE) in the product and construction stages is visible, with 46.52% and 37.24% of embodied GHG emissions reduced in CLT and hybrid CLT buildings, respectively, compared to the RC building. In the operational stage, RC building has lower PE and GHG emissions to CLT alternatives. The thermal mass effect has led to a 2.25% and 2.12% PE increase for space heating and cooling in CLT and hybrid CLT buildings, respectively, compared to the RC building. For the End-of-Life (EoL) stage, CLT demonstrates great recycling potential and biomass residues. The sensitivity analysis shows that the design of the low U-value of the building envelope and high-efficiency energy systems has a significant relationship with energy reduction during the operational phase of the three buildings, magnifying the impacts of the initial and EoL stages.