Natural Ventilation vs Fan-and-Pad Cooling
Cooling is where greenhouse ROI is won or lost in warm climates. Roof ventilation and pad-and-fan systems are the two dominant approaches — and they respond very differently to humidity, energy price and crop.
Natural roof ventilation
Continuous roof and side vents driven by wind and buoyancy, often paired with insect nets and internal shade screens.
Advantages
- Very low energy cost — no fans running through the day
- Simple maintenance, no water treatment for pads
- Works well in dry, breezy and mild climates
Limitations
- Limited cooling capacity — struggles above 32–34 °C ambient
- Depends on wind and structure geometry
- Insect nets reduce airflow and must be sized accordingly
- CAPEX:
- Included in most Venlo and multi-span structures
- OPEX:
- Minimal — maintenance and screen replacement only
- Best for:
- Highland tropics, Mediterranean, temperate Europe, mid-tech projects
Fan-and-pad evaporative cooling
Wet pads on one gable, extract fans on the opposite gable, air pulled across the greenhouse and cooled by evaporation.
Advantages
- Reliable 6–12 °C cooling below ambient in dry climates
- Predictable climate independent of wind
- Compatible with high-value crops in hot arid zones
Limitations
- High fan energy — 15–30 kW per hectare running continuously
- Ineffective in high-humidity coastal climates
- Water treatment and pad maintenance required
- CAPEX:
- €8–20/m² additional CAPEX
- OPEX:
- Dominated by fan electricity and water
- Best for:
- MENA, Sahel, arid inland zones, high-value tomato/pepper/cannabis
Our verdict
In dry inland climates, pad-and-fan is essential above ~32 °C summer peak. In humid coastal climates, natural ventilation plus high thermal screens and fogging usually beats pad-and-fan on both CAPEX and OPEX. In highland tropics, natural ventilation alone is often enough.
Independent guidance from a human-led sourcing platform — we do not resell equipment. Ranges are indicative and shift with project size, geography and financing structure.
FAQ
- Where does fogging fit into this decision?
- Fogging (high-pressure mist) is a complement, not a substitute. It raises humidity and reduces leaf temperature without moving as much air as pad-and-fan. In humid climates it pairs well with natural ventilation; in dry climates it can extend the useful range of pad-and-fan systems.
- How much energy does pad-and-fan really use?
- Rule of thumb: 15–30 kW per hectare of fans running 8–14 hours a day in peak season, plus 0.5–2 m³/ha/day of water. Solar hybridisation (see /solar-greenhouses) can absorb most of that daytime load.
- Are there hybrid designs?
- Yes — most modern high-tech greenhouses combine natural ventilation, thermal/shade screens, fogging, pad-and-fan and (in cold climates) heating and heat storage. The right mix depends on the climate curve at your site, not on a single vendor's product line.
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