Tunnel ventilation cools a poultry house by pulling air along its full length with exhaust fans at one end, through wet cooling pads at the other end. The air speed carries heat away from the birds, and the pads lower the air temperature. Fans are sized on the shed's cross-section and the target air speed; pads on the total fan airflow.
Why poultry need it
Birds cannot sweat. In hot weather they pant to lose heat, eat less, grow more slowly and lay fewer eggs, and on the hottest days losses rise. Moving air over the birds and cooling it before it reaches them reduces that heat stress.
How the system works
- Exhaust fans at one end of the shed pull air out.
- Fresh air enters through cellulose cooling pads at the other end.
- Water flowing over the pads cools the incoming air by evaporation.
- The cooled air travels the length of the shed, over the birds, and out through the fans.
Because all the air enters through the pads, the shed must be well sealed. Gaps let warm air bypass the pads.
Sizing the fans
The airflow needed is the shed's cross-section multiplied by the target air speed:
Airflow (m³/h) = width (m) × average height (m) × air speed (m/s) × 3,600
A common target in tunnel mode for broilers in hot weather is about 2.5 m/s; layers and breeders are often run lower.
Worked example: a shed 12 m wide with an average inside height of 3 m.
- 12 × 3 × 2.5 × 3,600 = 324,000 m³/h
- One 54 inch (1380 mm) fan moves about 44,000 m³/h
- 324,000 ÷ 44,000 = 7.4, so 8 fans
Sizing the pads
Air must pass through the pads slowly enough to cool well. Pad area = total fan airflow (m³/s) ÷ pad face velocity.
- 150 mm pads: about 1.8 m/s
- 100 mm pads: about 1.25 m/s
For the example: 8 × 44,000 = 352,000 m³/h = 97.8 m³/s. With 150 mm pads: 97.8 ÷ 1.8 = about 54 m² of pad.
Our poultry fan and pad calculator does this for you.
The pad wall
A complete pad wall includes the pads, a frame, a water pipe along the top, a gutter, a tank, a pump and a filter. Our PVC frame is the first made in India and does not corrode.
Good practice
- Seal curtains, doors and gaps so air enters only through the pads
- Run pad water only when it is hot enough to need it, to avoid wet litter
- Filter and clean the water; clean pads between flocks
- Check fan belts and shutters regularly, or use direct-drive fans to remove belts
See poultry fans and poultry farm cooling.
Frequently asked questions
What is tunnel ventilation in poultry?
Exhaust fans at one end pull air along the whole shed through cooling pads at the other end, cooling the air and moving it over the birds.
How many fans does a poultry shed need?
Width × average height × target air speed × 3,600 gives the airflow in m³/h; divide by the airflow of one fan, about 44,000 m³/h for a 54 inch fan.
How much cooling pad is needed?
Total fan airflow in m³/s divided by the pad face velocity, about 1.8 m/s for 150 mm pads or 1.25 m/s for 100 mm pads.