Ventilation protects plants from heat and disease.
Good ventilation removes excess heat and moisture, replaces stale air and helps leaves dry. It is not simply a summer comfort—it is part of plant-health management.
Use high and low openings
Hot air rises, so roof vents provide the main escape route. Louvres, side vents and an open door admit cooler replacement air. The exact opening needed changes with wind, sun, greenhouse size and crop density.
Automatic openers help, but still inspect
Wax-cylinder vent openers can react when nobody is present. Check their adjustment and movement regularly, and remember that a single roof vent may not ventilate a crowded greenhouse evenly.
Humidity is created by plants and watering
Transpiration, wet floors, open water and damp compost all add moisture. Water in the morning when possible, avoid permanently saturated compost and remove dead material. Space plants before their leaves overlap.
Overcrowding creates humidity and increases the risk of fruit rotting from botrytis. Remove affected material promptly and improve the conditions that allowed it to develop.
Fans are circulation, not replacement air
A fan can reduce stagnant pockets, but it does not remove heat or humidity unless air is exchanged with outside. Use electrical equipment suitable for the environment and position it so it does not scorch or batter nearby leaves.
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