The greenhouse environment can quickly become too hot for healthy plant production, even in the winter. During the summer months, extra cooling beyond what fan ventilation can provide may be necessary. Cooling pads cool by creating large amounts of surface area that are exposed to air being drawn into the greenhouse by exhaust fans. This large surface area allows for quick evaporation. Common pad materials include cellulosic materials or aspen fiber pads. Cellulosic pad materials are the preferred choice by most growers as they last longer than aspen pads.
The pad & fan cooling greenhouse system cools down temperature, using evaporative cooling. On hot summer days, this is an efficient way to cool small greenhouses, keeping the plants in the best climatic conditions. In addition, this system uses exhaust fans to absorb air from outside into the greenhouse. Firstly, the air is blown through the pad, which constantly evaporates water, creating a cooling effect. Then, the fans blow the cool air into the greenhouse, resulting in an overall decrease in temperature. Some greenhouses need to be cooled at night, mainly in tropical regions. However, the wet pad and fan system may not provide the desired results in tropical regions, where absolute humidity is often high at night.