Broiler Ventilation & Right Air, Right Fans

There are two regimes. Cold-weather minimum ventilation is sized on total live weight: rate (m³/h) = total bird weight (kg) × a per-kg factor that rises from about 0.012 in a cold brood house to 0.034 in a warm pre-tunnel house, scaled to an hourly basis. Hot-weather tunnel ventilation is instead sized on air speed: required airflow = house cross-section (width × height) × the target air speed × 3600. This tool runs both and tells you which regime your temperature falls in.

Tunnel ventilation cools big birds by wind-chill, so it is specified as an air speed past the birds, not a volume. Breeder guides target roughly 1.0 m/s in the transitional band, 1.75 m/s in moderate heat, 2.5 m/s in high heat and up to 3.0 m/s in severe heat. Heavy, older birds need the upper end, so the tool adds up to 0.6 m/s for birds above 2 kg. At 32 °C with 2 kg birds that works out to a 2.5 m/s target.

Fans needed = required airflow ÷ the capacity of one fan, rounded up. In tunnel mode the required airflow is cross-section × target air speed × 3600; in minimum-vent mode it is the live-weight-based rate. For example, a 15 m × 2.7 m house (40.5 m² cross-section) at a 2.5 m/s target needs 364,500 m³/h, which is 11 fans of 35,000 m³/h each. Enter your real fan rating to get the exact count.

Minimum ventilation is the smallest air exchange that still removes the moisture, ammonia and carbon dioxide the flock produces, without chilling the birds. It is run on a timer or static-pressure controller through inlets, not tunnel fans. Get it wrong and litter goes wet, ammonia climbs and respiratory disease follows — even though the house feels warm enough.

Above about 25 °C birds cannot lose enough heat by raising the air volume alone; what cools them is the wind-chill of fast-moving air over the skin. So tunnel houses are designed to a target air velocity (m/s or ft/min) measured at bird level, and the fan capacity is whatever delivers that speed through the house cross-section. This tool converts your target speed straight into the airflow and fan count required.

At 32 °C heavy broilers are in real heat-stress territory and need active cooling. A bird-level air speed around 2.5 m/s creates an effective wind-chill of several degrees, which is usually enough to hold them below the danger line; combined with evaporative cooling pads it offsets more. If your fans cannot reach that speed, the tool flags the shortfall and tells you how many fans to add.

Yes, strongly. Minimum ventilation scales directly with total live weight, so a house of 2.5 kg birds needs far more air than the same house of day-old chicks. Tunnel air speed also rises with weight because larger birds have less surface area per kilogram to shed heat, so this tool adds extra target speed for birds over 2 kg.

Use the clear internal width of the house multiplied by the average air height — usually the eave-to-floor or ceiling height through which tunnel air actually flows. The tool multiplies the two to get the cross-sectional area, then multiplies by the target air speed to get the airflow the fans must move. A 15 m wide, 2.7 m high house gives 40.5 m².

CFM is cubic feet per minute, the unit US fan ratings use; m³/h is cubic metres per hour, used elsewhere. One m³/h equals 0.5886 CFM, so 35,000 m³/h is about 20,600 CFM. The tool shows both — toggle the airflow units so you can match whatever your fan nameplate is rated in.

It uses published broiler-house ventilation engineering — live-weight minimum-vent factors and tunnel air-speed targets from breeder management guides and university extension housing tables. Real houses vary with inlet design, static pressure, leakage, evaporative cooling and controller settings, so treat the output as a sound design and audit figure, then confirm against your in-house temperature, ammonia and static-pressure sensors.

The minimum-ventilation and tunnel air-speed principles are the same for layers and breeders, but the per-kg factors and air-speed targets here are calibrated to broilers. For caged-layer or breeder houses, treat the result as a starting estimate and confirm against the specific breed management guide, since stocking style and heat output differ.