Evaporative Cooling Pad Guide for Poultry & Livestock Farms

An evaporative cooling pad is a honeycomb-structured cellulose medium that lowers incoming air temperature through the natural process of water evaporation. In poultry and livestock houses, it is the most energy-efficient method of reducing heat stress, improving feed conversion, and maintaining egg production during hot seasons. Water trickles down the corrugated pad surface while hot outside air is drawn through it by exhaust fans; the air cools by 5–12 °C depending on humidity. Correctly sized and installed cooling pads keep birds within their thermoneutral zone at a fraction of the operating cost of refrigerated air conditioning. This guide explains how evaporative cooling pads work, their specifications, applications in poultry and livestock farming, advantages, and practical selection criteria.

What Is an Evaporative Cooling Pad?

An evaporative cooling pad, also called a wet curtain or cellulose cooling pad, is a thick, corrugated sheet of specially treated cellulose paper arranged in a cross-fluted honeycomb pattern. Water is distributed across the top of the pad and flows down both the front and back surfaces, saturating the entire medium. When hot, dry outside air is pulled through the wet pad by negative-pressure exhaust fans, water evaporates from the pad surface and absorbs heat from the air. The air leaves the pad cooler and slightly more humid, and is then distributed throughout the animal house.

Unlike misting or fogging systems, evaporative cooling pads do not add free water droplets to the house air. This avoids wet litter, respiratory problems, and equipment corrosion. The pads are typically mounted in the side walls or end walls of a tunnel-ventilated building, with exhaust fans at the opposite end drawing air through the entire length of the house.

The Evaporative Cooling Principle

The cooling effect relies on the conversion of sensible heat into latent heat. As unsaturated air passes over the wet pad, water molecules absorb heat energy from the air and become vapour. The dry-bulb temperature of the air drops, while its relative humidity rises. The theoretical maximum cooling is the difference between the dry-bulb and wet-bulb temperatures, known as the wet-bulb depression. Modern cellulose pads achieve 85–92% of this theoretical maximum, giving practical temperature reductions of 5–12 °C in most poultry-farming regions.

Key Components of a Cooling Pad System

• Cellulose pad medium: Cross-fluted honeycomb paper, chemically treated to resist mould, algae, and rot.
• Pad frame: Aluminium alloy, galvanised steel, or stainless steel casing that holds the pad and distributes water.
• Water distribution pipe: Perforated PVC or stainless steel header pipe running along the top of the pad.
• Water collection trough: Bottom tray that collects unevaporated water and returns it to the tank.
• Circulation pump: Low-power pump (typically 0.37–1.1 kW) that lifts water from the tank to the header pipe.
• Water tank and filter: Reservoir with a mesh or sand filter to remove debris and prevent nozzle blockage.
• Exhaust fans: Tunnel-ventilation fans sized to pull air through the pad at the correct face velocity.
• Control system: Thermostat or climate controller that starts the pump and fans when house temperature exceeds the set point.

Typical Specifications of Evaporative Cooling Pads

• Thickness: 100 mm (4″), 150 mm (6″), 200 mm (8″) — thicker pads give higher efficiency and lower pressure drop.
• Flute angle: 45°/45° for standard cooling; 60°/30° for higher efficiency and lower resistance.
• Evaporation efficiency: 85–92% (150 mm pad), up to 95% for 200 mm premium media.
• Face velocity: 1.5–2.5 m/s through the pad (higher velocity increases pressure drop and reduces efficiency).
• Pressure drop: 15–30 Pa at 2.0 m/s for a 150 mm pad; 25–45 Pa for a 200 mm pad.
• Standard dimensions: Height 1500 / 1800 / 2000 mm; width 600 / 900 / 1200 mm; custom sizes available.
• Water flow rate: 4–8 L/min per metre of pad width.
• Material: Cellulose paper with special resin treatment; frame in aluminium, galvanised steel, or 304 stainless steel.
• Service life: 5–8 years with proper water treatment and annual cleaning; 10+ years with stainless steel frame and filtered water.

Applications in Poultry & Livestock Farms

Poultry Houses – Layers, Broilers & Breeders

Evaporative cooling pads are essential in tunnel-ventilated layer, broiler, and breeder houses in hot climates. Birds are highly susceptible to heat stress: when house temperature exceeds 30 °C, feed intake drops, egg production falls, shell quality deteriorates, and mortality rises sharply. Cooling pads lower the incoming air temperature by 5–12 °C, keeping the house within the bird’s thermoneutral zone (18–24 °C for layers, 18–22 °C for broilers). This protects production, improves feed conversion, and reduces mortality during heat waves.

Pig Farms – Gestation, Farrowing & Finishing

Sows and finishing pigs also suffer from heat stress, which reduces feed intake, lowers daily weight gain, and increases stillbirth rates in farrowing houses. Cooling pads provide effective temperature control in gestation barns, farrowing rooms, and finishing sheds. Because pigs are more sensitive to humidity than poultry, pads are usually operated at lower face velocities and combined with adequate ventilation to prevent excessive humidity buildup.

Dairy & Cattle Barns

In dairy operations, heat stress reduces milk yield by 10–25% and lowers fertility. Evaporative cooling pads installed in free-stall barns and holding pens provide a comfortable microclimate for high-producing cows. They are often used in combination with tunnel ventilation and recirculation fans to deliver cooled air directly to the cow lying area.

Greenhouses, Sheep & Rabbit Houses

The same principle applies in greenhouses, sheep sheds, rabbit houses, and equine stables. Cooling pads maintain a stable growing or living environment during summer, protecting plant yields and animal welfare. In greenhouses, they are often paired with shading screens and forced ventilation to achieve precise temperature and humidity control.

Key Advantages of Evaporative Cooling Pads

• Energy-efficient cooling: Consumes only the power of a small pump and the ventilation fans — typically 80–90% less energy than refrigerated air conditioning.
• Significant temperature reduction: Cools incoming air by 5–12 °C, depending on ambient humidity and pad thickness.
• Improved animal performance: Reduces heat stress, protecting feed intake, weight gain, egg production, and milk yield.
• Lower mortality: Prevents heat-related deaths during extreme summer conditions.
• No wet litter or droplets: Unlike misting systems, evaporative pads add only water vapour to the air, keeping bedding dry and reducing respiratory disease.
• Low maintenance: Requires only periodic cleaning, water quality management, and pump inspection.
• Long service life: Quality cellulose pads last 5–8 years; stainless steel frames extend life to 10+ years.
• Scalable and modular: Pads can be added in sections to match any house size or ventilation capacity.

How to Choose the Right Evaporative Cooling Pad

Pad Thickness and Cooling Efficiency

Thicker pads provide higher evaporation efficiency and lower pressure drop, but they occupy more wall space and cost more. As a general rule:

• 100 mm (4″): Efficiency 75–85%. Suitable for low-humidity regions and small houses.
• 150 mm (6″): Efficiency 85–92%. The most common choice for poultry and pig farms — best balance of performance and cost.
• 200 mm (8″): Efficiency 90–95%. Recommended for high-humidity areas or where maximum cooling is required.

Calculating the Required Pad Area

Pad area is determined by the total ventilation capacity of the house and the desired face velocity. The formula is:

Pad Area (m²) = Total Fan Capacity (m³/h) ÷ (Face Velocity (m/s) × 3600)

For poultry houses, a face velocity of 1.8–2.2 m/s is typical. For pig houses, 1.2–1.8 m/s is preferred to avoid excessive humidity. Always add 10–15% extra pad area as a safety margin for hot, humid days when efficiency drops.

Water Quality and Filtration

Water quality is the single most important factor affecting pad life and performance. Hard water causes scale buildup that blocks the corrugations; iron and manganese promote algae and bacterial growth; suspended solids clog the distribution holes. Install a sand filter or mesh filter on the water supply, and use a water softener if hardness exceeds 200 mg/L as CaCO₃. Recirculated water should be dumped and replaced at least weekly, or more often in dusty conditions. Some systems include automatic bleed-off valves to prevent concentration of dissolved solids.

Frame Material and Installation Orientation

• Aluminium frame: Lightweight, corrosion-resistant, and easy to install. Suitable for most farm environments.
• Galvanised steel frame: Stronger and more rigid, but can rust if the zinc coating is damaged. Good for large pads.
• 304 stainless steel frame: Best corrosion resistance for coastal or high-humidity farms; highest cost but longest life.
• Orientation: Pads are mounted vertically on the side wall or end wall. Ensure the pad is level and the water distribution pipe is horizontal. Allow a 300–500 mm air gap between the pad and any wall or obstruction on the outside to ensure uniform airflow.

Control and Automation

Modern cooling pad systems can be integrated with a farm climate controller. The controller monitors house temperature and humidity, and automatically starts the pump and increases fan speed when the temperature rises above the set point. It can also stage multiple cooling pad sections to avoid sudden temperature drops. For maximum efficiency, combine the cooling pad with tunnel ventilation and internal recirculation fans to distribute the cooled air evenly throughout the house.

Frequently Asked Questions