Greenhouse Cooling Pad and Exhaust Fan Sizing Basics

In hot climate greenhouse projects, a cooling pad and exhaust fan system is one of the most common ways to reduce inside temperature. The system uses exhaust fans to pull air through wet cooling pads. As water evaporates, the incoming air becomes cooler before moving through the greenhouse. Correct sizing is important. If the fans are too small, air exchange is weak and the greenhouse stays hot. If the cooling pad area is too small, air resistance increases and the system cannot work efficiently. If the layout is poor, some crop areas may receive cooler air while other areas remain hot. The first step is to confirm greenhouse dimensions. Length, width, height and total area affect required air volume. Crop type and plant density also matter because high density crops can block airflow. For long greenhouses, designers need to consider whether the fan and pad distance is suitable for even cooling. Local climate should be reviewed before choosing evaporative cooling. Cooling pads are more effective in hot and dry regions because evaporation is stronger. In hot and humid regions, the cooling effect may be limited, so roof ventilation, side ventilation, shade net and circulation fans may also be important. Fan selection should consider air volume, pressure, power supply, corrosion resistance and maintenance. Greenhouse exhaust fans are often installed on one end wall, while cooling pads are installed on the opposite side. The fan quantity should match the greenhouse area and required air exchange rate. Cooling pad selection should consider pad thickness, height, water distribution, frame material and service access. A good water circulation system is needed to keep the pad wet evenly. Filters and regular cleaning help reduce blockage from dust, algae or mineral deposits. A complete system also needs control logic. Temperature sensors, humidity sensors, water pump control and fan stages can help operate the system according to greenhouse conditions. Manual control may be enough for small projects, while larger farms often prefer automatic control. Buyers should prepare greenhouse drawings, crop information, local summer temperature, humidity and available power supply before requesting a quotation. This allows the supplier to recommend a more realistic fan and pad configuration. NSR Greenhouse can provide greenhouse cooling pads, exhaust fans, frames, pumps and matching structure design. Contact us with your greenhouse size and climate information to discuss a cooling system plan.