To achieve carbon-neutral target in building sector, reaching green building and ultra-low energy building (ULEB) goals are two progressive energy-saving targets for buildings in China. Previous studies have summarized and analyzed building carbon emission reduction potential effect by emphasizing technical comparisons based on determined single renovation energy target. Not enough focus has been given to connect renovation performance to economic feasibility in a comprehensive manner. An ultra-low energy office was selected and analyzed through life cycle assessment (LCA) method. Two progressive energy-saving targets were proposed: green building and ULEB. Carbon emission for green building and ULEB were calculated to be 5583 kgCO₂eq/m² and 3890 kgCO₂eq/m², with corresponding carbon emission reduction potential (CERP) of 17.6% and 42.6%, for the whole 50 years building lifespan. ULEB scenario, taking more aggressive energy saving strategies, demonstrated higher operational carbon emission reduction rate, but resulted in more embodied carbon emission. For economic feasibility evaluation, incremental cost and payback period were presented for both green building and ULEB. It was illustrated that incremental cost payback period (ICPP) of ULEB scenario is 22.1 years, 8.7 years more than green building. Compared with industry and transport sector, the CERP and ICPP value for green building was in a relatively medium level. However, the ICPP for ULEB was relatively high, making it a less preferred target if considering economic factors. The study could provide reference for government to develop carbon emission roadmap and policy for building retrofit in cold climate zone.