Greenhouse ventilation requires a minimum vent area equal to 15-20% of the floor space. A 6x8ft greenhouse needs at least 0.7 square metres of open venting. Ideal growing humidity sits between 40-60% for most crops. Automatic vent openers using wax cylinders activate at 15-20C and cost from 49 pounds. Damping down floors on hot mornings raises humidity by 15-25%, reducing heat stress and spider mite risk.
Key takeaways
- Total vent area should equal 15-20% of floor space for adequate air exchange
- Automatic vent openers activate at 15-20C using wax cylinders and need no electricity
- Ideal greenhouse humidity for most crops is 40-60% relative humidity
- Louvre vents at low level draw cool air in while hot air escapes through roof vents
- Damping down floors on hot mornings raises humidity by 15-25% and cools the air
- Poor ventilation above 30C causes heat stress, flower drop, and blossom end rot in tomatoes
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