A numerical study was carried out to investigate the micro-climatic environmental conditions inside a greenhouse-distillation system, self-sufficient for irrigating water. The greenhouse consists of the planting cavity, circulating air channels and roof solar distiller for the production of a rather modest rate of irrigating water. A turbulent, steady-state flow, energy and humidity concentration equations were solved using the numerical code FLUENT 6.1. Velocity vectors, steam function, isotherms and temperature and humidity distribution inside the greenhouse present the resultant micro-climatic environmental conditions. The results are presented for hot days where cold and humid air (from the evaporative cooler) enters the greenhouse from one side and is circulated through the partially porous cavity (representing the plants) and flows through air flow channels and leaves from a vertical thermal chimney. The results show that, with the selected inlet flow conditions, the flow velocity, temperature, and relative humidity can be within the comfort values for plant growth. The effect of some important environmental, design, and operational parameters on greenhouse micro-climatic conditions has also been highlighted.