In a greenhouse, mesh size plays a far bigger role than just regulating ventilation.
It directly influences temperature, humidity, airflow resistance, and even radiation balance, all of which shape plant growth performance.
Understanding these microclimate interactions helps growers fine-tune the environment for higher yield, lower disease pressure, and more efficient climate management.
How does mesh size impact greenhouse conditions beyond ventilation?
Besides controlling ventilation rate, mesh size significantly affects thermal accumulation and moisture retention inside a greenhouse.
Smaller mesh sizes restrict air exchange, causing:
- Higher temperature (typically +1°C to +3°C with 75-mesh vs 50-mesh)
- Higher absolute humidity
- Slower vapor removal（higher VPD pressure）
This microclimate shift affects not only comfort conditions for crops but also pest behavior, fungal incubation periods, transpiration rates, and energy use for cooling systems.
Mesh Size vs Microclimate Effect (Quick Comparison Table)
| Mesh Size | Airflow | Temperature | Humidity | Pest Control | Suitable For |
|---|---|---|---|---|---|
| 25–32 Mesh | High | Slightly higher (0–1°C) | Low–Moderate | Large insects | Hot climates needing max ventilation |
| 40–50 Mesh | Moderate | +1–2°C | Moderate | Whiteflies, aphids | General-purpose greenhouses |
| 60–75 Mesh | Low | +2–3°C | High | Thrips & tiny insects | Cool climates, winter seasons, protected crops |
Key Points to Understand
Temperature Impact
Smaller mesh sizes trap heat because the reduced ventilation makes it harder for hot air to escape.
This causes heat buildup, especially on windless days.
Higher temperatures may:
- Benefit heat-loving crops (tomatoes, cucumbers, peppers) by extending warm nights.
- Harm cool-season crops (lettuce, spinach) by increasing bolting or leaf burn.
Technical Insight:
Fine mesh reduces the greenhouse’s convective cooling efficiency. As air movement decreases, leaf boundary layers thicken, limiting plant cooling through transpiration.
Humidity Control
Restricted airflow means moisture from transpiration stays inside longer.
This results in:
- More stable humidity
- Greater leaf turgor
- Lower evapotranspiration demand
But also:
- Higher risk of Botrytis, powdery mildew, and downy mildew
- Difficulty maintaining a proper VPD（Vapor Pressure Deficit）
Technical Insight:
75-mesh netting may reduce VPD below 0.8 kPa in mild climates — a range where fungal diseases thrive.
Energy Efficiency
A greenhouse with reduced ventilation caused by small mesh sizes often requires:
- Higher fan power
- More frequent vent opening
- Active dehumidification or circulation fans
This increases electricity use, especially during summer.
Technical Insight:
Studies show fine-mesh screens can increase fan energy consumption by 12–22% due to airflow resistance.
Plant Growth
Temperature and humidity shifts from mesh size strongly impact crop physiology:
Possible Benefits
- Faster vegetative growth
- Lower water demand
- Less leaf dehydration
- Better early-season establishment
Possible Risks
- Delayed flowering
- Lower pollination (high humidity reduces pollen viability)
- Elongated stems in low-VPD conditions
Technical Insight:
High humidity reduces stomatal regulation and calcium mobility — increasing blossom end rot risk in tomatoes.
Climate Adaptation
Mesh size allows a greenhouse to be “tuned” for different climates:
Hot climates
Use 25–40 mesh → maximize airflow, prevent overheating.
Humid subtropical climates
Use 40–50 mesh → balance pest control & ventilation.
Cool/windy climates or winter seasons
Use 60–75 mesh → conserve heat and moisture.
Technical Insight:
Fine mesh increases nighttime temperature retention, reducing heating costs in winter tunnels.
Customer Experience
Optimizing Vegetable Greenhouses (Spain)
A greenhouse vegetable grower in Spain switched from 50-mesh → 40-mesh to reduce humidity and lower internal temperatures.
Results showed:
- Fewer fungal outbreaks
- Better airflow
- Higher fruit firmness
- ~12% yield improvement in peppers
Tomato Production in Chile
A tomato grower in Chile used 75-mesh to retain warmth during winter.
The warmer, more humid environment accelerated early growth, thereby improving early-season yield.
However, the grower needed:
- Exhaust fans
- Horizontal airflow fans
To counteract humidity rises, highlighting the importance of airflow management when using fine nets.
FAQ – Insect net mesh size affects Microclimate
How can mesh size influence pest control in greenhouses?
Smaller mesh sizes block small pests such as:
- Thrips
- Leaf miners
- Whiteflies
- Aphids
However, overly fine mesh can reduce ventilation to the point that humidity rises, encouraging fungal diseases.
Growers must balance pest exclusion ability + airflow performance.
Does mesh size affect UV protection in greenhouses?
Yes.
Smaller mesh provides more shading and UV filtering, creating:
- Better protection from leaf scorch
- Lower UV stress
But excessive shading reduces photosynthesis and delays fruit coloration.
Does fine mesh reduce light levels inside the greenhouse?
Yes — fine mesh slightly reduces PAR (photosynthetically active radiation), especially at high mesh counts.
The reduction is small (2–8%) but meaningful for light-dependent crops.
Can fine mesh increase fungal disease risk?
Yes.
Higher humidity + lower VPD = perfect conditions for:
- Botrytis
- Powdery mildew
- Alternaria
Ventilation fans or periodic vent opening are recommended.
Which mesh is best for warm climates?
Hot regions benefit from 25–40 mesh, ensuring maximum airflow and preventing heat buildup.
Which mesh is best for thrips control?
Thrips require 50–75 mesh.
Most growers use 50 mesh for balance, 75 mesh when thrips pressure is severe and climate is cool.
Conclusion
Mesh size is a fundamental variable shaping greenhouse microclimate — not just pest protection.
It affects ventilation rate, temperature, humidity, UV exposure, energy consumption, and plant health.
Choosing the correct mesh allows growers to achieve:
- Better crop quality
- Lower disease pressure
- More stable internal climate
- Higher production efficiency
Optimize Your Greenhouse Environment with the Right Mesh Size!
Mesh size controls ventilation, thermal load, humidity, and pest entry — all critical for crop performance.
At EyouAgro, we provide insect netting from 25–75 mesh designed for:
- Vegetable greenhouses
- Fruit nurseries
- Seedling houses
- High-tech climate-controlled tunnels
Need help selecting the perfect mesh for your greenhouse?
Contact our experts today for personalized advice and ensure optimal crop conditions.
