Greenhouse Ventilation: The Key to Healthy Plants
It might seem counterintuitive—why would a greenhouse, designed to trap heat, need ventilation? The answer is simple: plants need fresh air, and without proper airflow, your greenhouse becomes a breeding ground for problems.
Why Ventilation Matters
- Temperature control — Prevents overheating on sunny days
- Humidity management — Reduces fungal diseases
- CO2 replenishment — Plants need carbon dioxide for photosynthesis
- Pollination — Some plants need wind for pollen movement
- Strengthens plants — Gentle breeze toughens stems
Signs of Poor Ventilation
- Condensation dripping from plants
- Mold or mildew on leaves
- Leaves curling or yellowing
- Temperatures soaring above 90°F
- Stunted growth
Ventilation Options
Passive (No Power Needed)
- Roof vents — Hot air rises, escapes through top
- Side vents — Cross-breeze effect
- Louvered vents — Adjustable airflow
- Open doors — Simple but effective
Active (Powered)
- Exhaust fans — Pull air out forcefully
- Circulation fans — Move air within greenhouse
- Automatic vent openers — Open/close based on temperature
Pro Tips
- Cross-ventilation is best — Entry and exit points on opposite walls
- Size matters — Vents should equal 15-20% of floor area
- Shade + vent together — Reduces heat before it builds
- Winter ventilation — Still needed! Crack a vent on sunny winter days
Need help with pests? See our Greenhouse Pest Control Guide.
Frequently Asked Questions
Greenhouse Ventilation FAQs
Q: Why is greenhouse ventilation important?
A: Proper ventilation controls temperature, humidity, and air circulation. It prevents overheating, reduces disease, and provides fresh CO2 for plant photosynthesis.
Q: How do I improve ventilation in my greenhouse?
A: Install roof vents and side vents, use exhaust fans, add oscillating fans, and ensure proper airflow paths. Automatic vent openers help maintain consistent ventilation.
Q: What temperature should I ventilate?
A: Start opening vents when temperatures reach 70-75°F. At 85°F+, use maximum ventilation and consider shade cloth.
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