Development and Cradle-to-Gate (A1–A3) Carbon Emission Assessment of Modular Bathroom Wall Panels for Residential Buildings

Purpose: This study aimed to develop a modular bathroom wall panel applicable to residential buildings and to verify its potential for embodied carbon reduction within the cradle-to-gate (A1–A3) stage. By comparing conventional wet and existing modular construction methods, a lightweight and low-carbon wall system was proposed. Method: Large-format wall materials such as pre-painted steel, enamel-coated steel, and composite boards were evaluated according to KS F 2223 and KS L 1001 standards. Mock-up tests for deflection and impact were conducted to validate performance, and the embodied carbon emissions (A1–A3) were calculated based on material quantities and emission factors. Result: Pre-painted steel satisfied all performance criteria and was selected as the optimal material. The developed wall panel achieved 19% of the total weight of wet construction and 60% of the existing modular wall, while reducing A1–A3 emissions to 87% and 82%, respectively. The results demonstrate that modularization and material substitution can effectively reduce embodied carbon during early construction stages.