The temperature in a vegetable factory and that in a heat-insulation room are kept at adequate temperature, and further the temperature distribution can be uniform by eliminating temperature variation. The adequate temperature in a facility can be kept by continuing the operation of a private electric generator. The influence of the radiated heat from the outside air on the plant growth can be mitigated without using any heat-insulating material. As a result, vegetables with more uniform sizes can be cultivated, and the power consumption of the air-conditioning power can be reduced.
