Greenhouse Ventilation Calculator
Proper ventilation is critical for greenhouse success. Calculate the optimal CFM (Cubic Feet per Minute) and determine fan size requirements for your greenhouse based on volume, desired air changes, and temperature differential.
Ventilation Calculator
Understanding Greenhouse Ventilation Requirements
Key Ventilation Factors
- Air Changes Per Hour: Most greenhouses need 15-20 air changes per hour for cooling
- Temperature Differential: Exhaust fans activate when inside temp exceeds outside by 5-10°F
- Fan Capacity: Size exhaust fans for 60-75% of calculated CFM
- Intake Area: Provide 1.5x exhaust fan area for passive intake
Ventilation Guidelines
- Small Greenhouse (<200 sq ft): 1-2 exhaust fans, natural intake
- Medium Greenhouse (200-800 sq ft): 2-4 exhaust fans with intake fans
- Large Greenhouse (>800 sq ft): Multiple zones with automated controls
- HAF Fans: Add horizontal airflow fans for air circulation
Ventilation System Components
| Component | Purpose | Sizing Rule |
|---|---|---|
| Exhaust Fans | Remove hot, humid air | 60-75% of calculated CFM |
| Intake Vents | Allow fresh air entry | 1.5x exhaust fan area |
| HAF Fans | Horizontal air mixing | 1 CFM per 2-3 sq ft floor |
| Thermostats | Temperature control | Multi-stage for fan staging |
Installation Tips
- Position exhaust fans at the highest point for heat removal
- Place intake vents near ground level on opposite end
- Install thermostats away from direct sunlight and heat sources
- Use shutters on exhaust fans to prevent backdraft when off
- Consider variable speed controls for energy efficiency
- Maintain fans regularly - clean blades and louvers seasonally
⚠️ Important Notes
- These calculations provide baseline requirements - consider local climate conditions
- High-humidity regions may need increased ventilation capacity
- Plants with high transpiration rates require additional air movement
- Winter ventilation needs are typically much lower than summer requirements