The first priority in cooling a greenhouse is optimizing air movement. Sound ventilation design prevents the accumulation of hot, humid air, which in turn suppresses pathogen development. Under high-temperature conditions, a greenhouse should complete one full air exchange per minute, with the minimum acceptable rate no lower than one exchange every two minutes.

The most effective strategy combines passive and active mechanical ventilation:

• Passive ventilation: This relies on the "chimney effect," in which hot air rises and escapes through roof vents while cooler fresh air enters through side vents. Automatic vent openers are a key efficiency upgrade, adjusting according to preset temperatures to keep the air-exchange rate stable.
• Active ventilation: Exhaust fans and horizontal airflow (HAF) fans drive forced convection, while HAF fans circulate air internally to eliminate localized temperature differences and keep the growing environment consistent across the crop.

When ambient temperatures exceed what ventilation alone can manage, active cooling becomes a necessary supplement. Two mainstream approaches are compared below.

Caution: Wet-pad and fogging systems cool by raising air humidity, so they should be used carefully in humid regions, where excess moisture can increase the risk of disease.

Shade systems reduce the radiant heat entering the greenhouse and ease the load on ventilation and cooling equipment. Common configurations include:

• External shading: Blocks light outside the structure for a pronounced cooling effect, though installation costs and complexity are comparatively high.
• Internal shading: Truss-to-truss systems are the mainstream choice, offering the advantage of minimal space use and a compact bundle when retracted.

Growers can select materials with shade ratings of 30 percent to 70 percent, and should favor UV-resistant or reflective shade cloth for stronger temperature control.