A numerical model has been developed to simulate volatile organic compound (VOC) emissions from 'wet' coating materials. The model considers the VOC mass transfer process in the air and material-air interface, and diffusion in the material film and also in the substrate. Our numerical simulations confirmed that the emissions from wet materials applied to an absorptive substrate are dominated by evaporation at the beginning followed by internal diffusion, which had been hypothesized based on previous experimental data. The numerical model has been validated based on the data from small-scale environmental chamber tests.