Carbon Footprint Analysis of Residential Buildings in Japan

The decarbonization of the building sector is a critical challenge for achieving Japan’s net-zero targets. However, comprehensive assessments comparing residential construction methods and building heights at the national scale remain limited. This study applies Environmentally Extended Input–Output Analysis (EEIOA) to evaluate the embodied CO2 emissions associated with four distinct residential construction methods. The results reveal that, when accounting for carbon storage, the net CO2 emissions per unit of floor area were significantly lower for wooden houses (195 kg-CO2/m2) compared to steel-reinforced concrete (1109 kg-CO2/m2), reinforced concrete (857 kg-CO2/m2), and steel-framed houses (803 kg-CO2/m2). A further analysis based on building height indicates a structural divergence: while wooden houses account for the majority of emissions in one- to three-story buildings due to their high market share, reinforced concrete houses dominate emissions in four- to nine-story buildings driven by their high carbon intensity. These findings suggest that promoting timber construction, particularly in taller buildings, is a vital strategy for climate change mitigation. Consequently, policy support focusing on technological advancement, cost reduction, and consumer awareness is essential to accelerate the adoption of wooden architecture.