This paper presents a new laboratory measurement setup for determination of the evaporation rate of material samples under controlled natural and forced convective air flow boundary conditions. Automatic measurements of the vapour flux and surface temperature at different adjusted air humidities and air temperatures are conducted by using wind channels placed in a climatic chamber. In addition, a new functional approach is proposed to account for the free stream air velocity and surface structure (roughness) dependency of the heat and mass surface transfer coefficients. The parameters of the functional approaches are determined by the measurements and results of six different materials are presented and analysed.