Maximum and minimum air temperatures (Ff) were recorded daily with Taylor max-min thermometers both inside and outside the greenhouse beginning March 1979.

Fig. 1 shows a generalized view of the mean monthly greenhouse temperatures for a typical 12 month period. Over the entire year, the mean temperature averaged 12f warmer than outside.

Average monthly max/min temperatures inside and outside the greenhouse are shown in Fig 2.

The average yearly max/min temperature inside the G.H. was 90f/55f while the outside averaged 78f/43f.

During the design phase we had anticipated problems with overheating during the summer months. Until we had actually built and monitored this greenhouse, we anticipated several solutions to this perceived problem from shading to actually removing the membrane during the summer months.

Ventilation: From May through August 17% of the daily maximum temperatures were actually lower than outside (without shading or misting) with a difference of as much as 10° being recorded. This is most likely due to evaporative cooling resulting from evaporation of moisture from the irrigated soil body and transpiring plants and venting by the Chimney effect.

Shading lowered the maximum temperatures an average of 5f.

Misting lowered the maximum temperatures an average of 7f.

Ventilation, misting and shading were each shown to effectively lower the temperatures in summer. It seems apparent that the simulatneous use of misting and shading in conjunction with planting of heat-tolerant varieties could further increase the summer effectiveness of the greenhouse for such crops as lettuce.