The fundamental heat/mass transport mechanism from the vapor-generating surfaces related to interfacial solar vapor generators for desalination applications has received less attention. The majority of the investigations in this regard were not carried out inside controlled environmental facilities, and the operating conditions for different proposed configurations in the literature varied. Although few investigations have reported theoretical framework and computational simulations of the heat/mass transport phenomena during the interfacial evaporation involved in such cases, no systematic experimental investigation exists in the literature. In the present study, a controlled environmental test section capable of having different far-field ambient conditions and maintaining a quiescent environment, is designed and fabricated. The performance of a thermosyphon-based heat localization strategy proposed by the authors for efficient and reliable vapor generation was tested in this test section. Different far-field ambient conditions (RH = 30%–80% and T_amb = 25–42 °C) are investigated on the evaporating mass flux and heat-to-vapor conversion efficiency. The experimentally obtained evaporative mass flux was compared against three Sherwood–-Rayleigh empirical correlations for natural convection-driven evaporation. It was shown that the existing relations matched well for the cases that fell within the assigned range of Rayleigh number of these correlations.