A system passively cools, regulates humidity and/or rectifies diffusive transport of water vapor in an interior area within a structure. The system includes a membrane assembly covering a portion of the structure, wherein the membrane has an interior side facing the interior area and an exterior side. The membrane assembly defines a plurality of pores. When cooling, a supply of fluid is provided to the membrane assembly so that capillary action of the pores redistributes the fluid to create evaporation and, in turn, the desired heat flow. The membrane assembly can include an architectural membrane coated with a porous matrix coating to form the pores. A pump can provide the fluid to the interior side of the membrane assembly. Preferably, the architectural membrane is woven PTFE-coated fiberglass and the porous matrix coating is titanium dioxide, zeolites and/or silica gel.