Cooling Pads vs Fogging — Poultry House Cooling Compared
Both systems cool by evaporating water into the air, and both are limited by the same physical ceiling: the outside wet-bulb temperature. Pads evaporate at the inlet wall before air enters the house; fogging evaporates inside the house, in the air the birds are already breathing. That single difference drives every other trade-off.
Evaporative cooling pads
- Evaporation happens outside the bird zone — no wet litter if the system is sized correctly
- Stable, predictable ΔT at a known face velocity
- Coarse water tolerance is higher than fogging nozzles
- Well understood by contractors in almost every market
- Adds static pressure, so fans must be sized for the pad face
- Pad fouling, scaling and algae need continuous water treatment and bleed-off
- Requires a tunnel-ventilated, sealed house to work at all
- Higher CAPEX and a fixed structural commitment
- — Sealed tunnel-ventilated broiler houses in hot-dry climates
- — Design outside temperature ≥ 34 °C with a wet-bulb depression above 8 °C
- — New-build projects where the inlet wall is being designed anyway
High-pressure fogging
- Much lower CAPEX and no inlet wall rebuild — retrofits into existing houses
- Can be staged and zoned, including brooding-area humidification
- No permanent pressure drop across the inlet, so fan energy is unaffected
- Works in naturally ventilated and open-sided houses where pads cannot
- Any nozzle that does not fully evaporate wets litter and drives ammonia and footpad lesions
- Nozzles block without fine filtration — typically 5 µm and softened water
- Less ΔT per litre in practice because droplets fall out before evaporating
- Humidity in the bird zone rises immediately, so control must be humidity-aware
- — Retrofits into existing houses without a tunnel inlet wall
- — Open-sided and naturally ventilated houses
- — Hot-humid climates where pads deliver little ΔT and zoned relief is the realistic goal
- — Breeder and layer houses needing humidity control during brooding
| Criterion | Evaporative cooling pads | High-pressure fogging |
|---|---|---|
| CAPEX | Higher — pad wall, sump, pumps, distribution, inlet rebuild | Lower — pump skid, lines, nozzles, filtration |
| OPEX | Water treatment, bleed-off, annual pad replacement in hard water | Nozzle cleaning and replacement, fine-filter cartridges |
| Energy | Circulation pump plus a permanent fan penalty from pad pressure drop | High-pressure pump only; no added fan load |
| Maintenance intensity | Scheduled — water chemistry is the whole job | Frequent — nozzle inspection is a weekly discipline, not an annual one |
In hot-dry climates with a sealed tunnel house, pads are the stronger system and the extra CAPEX is recovered in stable ΔT. In hot-humid climates neither system delivers large temperature drops — the wet-bulb depression is simply too small — and fogging's lower cost and zoning make it the pragmatic choice alongside higher air speed. For retrofits into houses that were never built for tunnel, fogging is usually the only system that fits. Size cooling against your site's design wet-bulb, not its dry-bulb: when the wet-bulb depression is under 6 °C, both options mostly add humidity, and air speed over the birds does more good than either.
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