This study deals with the effect of using two layers of polyethylene tightly fixed together along the frame elements of the walls and the roof, the space between the films was inflated at a pressure of 50 Pa, on, the effectiveness of evaporative cooling system during hot period, energy transport characteristics during cold period, and most relative vegetative growth parameters and production of egg-plant crop under eastern province climatic conditions of Saudi Arabia. These parameters were studied and compared with the commonly used double layers (without air gap) covering method. The results of this experimental work show that the greatest values of cooling ef­fect (16.60°C) and effectiveness of evaporative cooling system (81.5%) were achieved inside the greenhouses covered with double layers of polyethylene with 9 cm air gap (G1), whereas, the effectiveness of cooling sys­tem (76.2%) occurred inside the greenhouse covered by double layers of polyethylene without air gap (G2). Consequently, Greenhouse 1 increased the effectiveness of cooling system by 5.3%. At nighttime the heat flux at the soil surface normally contributes heat energy to the greenhouse air, by releasing heat energy stored from the absorption of solar radiation at the floor surface on the previous daylight. Inside the greenhouse heat is transferred from the floor surface to the inside air by natural convection and thermal radiation emits from the floor or a uniform horizontal canopy surface of egg-plant.  The hourly averages solar radiation recorded outside and inside the two greenhouses was 563.8, 273.8, and 300.7 Wm^–2, consequently, the effective reflectance, absorption, and transmittance of the covering methods was on the average 48.56% and 53.34%, respectively. The air temperatures within the two greenhouses were at or around the desired level particularly in the greenhouse 1. Thus, the egg-plants were grown well during the experimental period. Moreover, the greenhouse 1, on the average, in­creased the rate of vegetative growth by 30.30% and fresh yield of egg-plant crop by 32.68%.