Saved scenario comparison
| Name | Shape | Dimensions | ACH | Fan airflow | Shade | Target RH | Action |
|---|
Formula used
Air-change airflow: Q = V × ACH.
Heat airflow: Q = H ÷ (ρ × Cp × ΔT).
Humidity airflow: Q = moisture ÷ humidity-ratio difference.
Fan quantity: N = ceiling(design airflow ÷ effective fan airflow).
Natural airflow: wind and stack components combine quadratically.
The calculator converts all entries into consistent internal units. It compares independent airflow requirements before adding the safety margin. The largest applicable requirement controls the final ventilation design.
How to use
- Select metric or imperial units.
- Enter greenhouse dimensions and shape.
- Set environmental and crop conditions.
- Add fan, vent, inlet, and cost information.
- Choose a calculation mode.
- Submit the form and review warnings.
- Export results or save comparison scenarios.
Use realistic design-day values for reliable estimates. Check fan ratings at expected static pressure. Confirm final selections with qualified greenhouse professionals before purchasing equipment.
Example data
| Input | Example | Purpose |
|---|---|---|
| Dimensions | 30 × 10 × 3–5 m | Defines floor area and air volume. |
| Air changes | 30 ACH | Sets a baseline ventilation rate. |
| Solar radiation | 700 W/m² | Estimates transmitted solar heat. |
| Fan rating | 30,582 m³/h | Determines required fan quantity. |
| Screen porosity | 70% | Reduces effective opening area. |
| Electricity rate | £0.28/kWh | Estimates operating expenses. |
Frequently asked questions
What airflow method should I use?
Automatic mode compares every available method. It selects the largest airflow requirement. This approach reduces the chance of undersizing equipment.
How many air changes are typical?
Suitable rates depend on season and crop conditions. Summer cooling often requires much higher rates. Always verify recommendations for your local climate.
Why does humidity airflow become zero?
Outdoor air must be drier than target indoor air. Otherwise ventilation cannot remove moisture effectively. Dehumidification or heating may become necessary.
How are screen losses handled?
Screen porosity reduces natural opening effectiveness. Mechanical screening losses reduce effective fan airflow. Enter manufacturer-tested values whenever available.
Does fan efficiency equal motor efficiency?
No, they describe different performance effects. Fan performance adjusts delivered airflow. Motor efficiency adjusts electrical input power.
Can this calculate natural ventilation?
Yes, it estimates wind and stack airflow. It also sizes matched roof and side openings. Local obstruction effects still require professional review.
What does governing method mean?
It is the largest calculated airflow requirement. Smaller methods remain visible for comparison. The design margin applies after selecting it.
Why include backup fans?
Backup capacity supports reliability during failures or maintenance. It also helps during extreme weather. Critical crops may require larger redundancy allowances.
How accurate are operating costs?
Costs depend on real fan loading and schedules. Variable-speed operation can greatly reduce energy consumption. Compare estimates with measured utility data.
Does this replace engineering design?
No, it provides planning-level estimates only. Structural, electrical, and safety requirements still apply. Obtain professional approval before final installation.