How Does Evaporative Cooling Design Work in Greenhouses?

I take the greenhouse design cooling load — solar gain through the glazing dominates — and the local design wet-bulb, then calculate the airflow needed to carry that load at the achievable supply temperature. Pad area follows from airflow at the manufacturer's rated face velocity; fan capacity follows from airflow plus the static pressure of pads, house length, and any shading or screening. I check performance at both the design dry day and a humid spell, and I document the expected interior conditions for each so the grower knows what the system can and cannot do. Water supply is sized to the evaporation rate with recirculation and bleed, and the sump and pump station are designed for service access.

Pad life is a water-treatment problem: I specify filtration, bleed-off rates, and any treatment the source water analysis calls for, plus sump designs that drain fully so pads dry out between cycles. The climate computer sequences wetting ahead of fan staging and backs the system down on humidity — cooling that soaks the crop invites disease. Alarms cover pump failure and sump low-water, because running fans over dry pads just moves hot air. In California, regulated energy aspects follow the 2025 California Energy Code / 2025 Standards, effective January 1, 2026.

A greenhouse evaporative cooling design is summer-ready when it clears this checklist. It is a climate-specific system — every item ties back to what the local air can do. • Cooling capacity calculated from design wet-bulb depression, not from rules of thumb • Pad area sized to design airflow at rated face velocity with even distribution • Exhaust fans sized for full cooling airflow in a tunnel or cross-flow pattern • Water supply, recirculation, and bleed-off designed to the evaporation rate • Water treatment and dry-out cycling specified for pad life • Controls staging pad wetting with fan speed on temperature and humidity