With no direct sunlight entering through the north wall of the greenhouse and maximum heat loss occurring there, the north wall is an energy liability. Some commercial and university greenhouse ranges are experimenting with full ground-to-roof insulation of the north wall, using concrete or wood and appropriate insulating material. The energy saved is proving to be significant and the light reduction minimal.
Thermal Blanket Over Crops
Most of the heat loss in a greenhouse occurs after dark; hence, that is when fuel consumption is greatest. Heating the air between the crop and the greenhouse roof at night has been a necessary evil in the past, although admittedly of no value to the plants. Now a thin thermal blanket supported on wires can be pulled over the plants at night to hold warmth around the benches where it is needed.
The principal drawback to this technique can be the awkwardness of its operation. If hand-pulled across the crop, it results in a loss of some daylight because the greenhouse staff does not report for work at sunrise each day nor work until dark. Automated blanket systems have been developed and are gaining industry acceptance nationwide.