Broiler Ventilation & Right Air, Right Fans
Sizes minimum vent
A broiler house needs two different jobs from its fans: minimum ventilation to clear moisture and ammonia in the cold, and tunnel air speed to cool birds by wind-chill in the heat. Enter the flock, house size and temperature to get the ventilation rate, target air speed and the number of fans you actually need.
Set up the broiler house
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Next: run a 11-fan tunnel bank (35,000 m³/h each) to hold 2.54 m/s past the birds at 32°C — that meets the heat target.
Engineering planning figures from broiler-house ventilation standards (Cobb/Ross management guides + university extension poultry-housing tables). Minimum-vent rate is sized on total live weight; tunnel air speed is sized for wind-chill cooling. Always confirm against in-house temperature, ammonia and static-pressure sensors.
Poultry ventilation — key facts
- Minimum vent
- total live-weight × per-kg factor
- Tunnel airflow
- cross-section × air speed × 3600
- Tunnel target
- ≈ 2.5 m/s in high heat
- Tunnel engages
- above ~25 °C
- Fans needed
- airflow ÷ fan capacity, round up
- 1 m³/h
- = 0.5886 CFM
- 1 m/s
- = 196.85 ft/min
- Heavy-bird bump
- +0.18 m/s per kg over 2 kg (max 0.6)
- Privacy
- Runs in your browser; nothing uploaded
Two ventilation jobs, one house
A broiler house has to do two very different things with its fans depending on the weather. When it is cold, the goal is minimum ventilation: move just enough air to carry out the water vapour, ammonia and carbon dioxide the flock produces, without throwing cold air on the birds. That rate scales with the total live weight in the house — a shed of 2.5 kg birds breathes out far more moisture than the same shed of chicks — so it is sized as live weight times a per-kilogram factor.
When it is hot, raising the air volume is not enough. Birds shed heat to fast-moving air by wind-chill, so a hot house switches to tunnel ventilation, sized to a target air speed past the birds rather than a volume per bird. The required airflow is simply the house cross-section times that target speed; divide by your fan rating and you have the fan count. This tool runs both regimes, picks the right one for your temperature, and flags when your installed fans cannot reach the target speed — the moment heat stress begins.
Ventilation rate reference tables
| Band | Temp | /kg | Purpose |
|---|---|---|---|
| Cold (brood/winter) | ≤ 18 °C | 0.012 | clear moisture/ammonia only |
| Cool | 18–24 °C | 0.018 | rising sensible & moisture load |
| Mild | 24–28 °C | 0.026 | transitional, fans cycling up |
| Warm (pre-tunnel) | > 28 °C | 0.034 | max before tunnel engages |
| Band | Temp | m/s | Note |
|---|---|---|---|
| Comfort | ≤ 25 °C | 0 (min vent) | no wind-chill needed |
| Transitional | 25–28 °C | 1.0 | first tunnel stage |
| Moderate heat | 28–30 °C | 1.75 | steady tunnel |
| High heat | 30–33 °C | 2.5 | heavy birds at upper end |
| Severe heat | > 33 °C | 3.0 | + evaporative cooling |
Sources: Cobb & Aviagen/Ross broiler-house management and environmental-control guides; university extension poultry-housing ventilation tables. Figures are design planning values; confirm against in-house sensors.
How to size your ventilation in five steps
- 1
Enter the flock
Number of birds and current weight — together these give the total live weight that drives minimum ventilation.
- 2
Enter the house
Width and air height set the tunnel cross-section; enter the rated airflow of one of your fans.
- 3
Set the temperature
Type the house temperature; the tool decides whether you are in minimum-vent or tunnel mode.
- 4
Read the requirement
See the minimum ventilation rate (m³/h & CFM) or the target tunnel air speed and the airflow it demands.
- 5
Check the fans
The tool counts the fans needed and warns if your bank cannot reach the target air speed in peak heat.
Frequently Asked Questions
How do I calculate the ventilation rate for a broiler house?+
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.
What is the target tunnel air speed for broilers?+
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.
How many fans does my broiler house need?+
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.
What is minimum ventilation and why does it matter in cold weather?+
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.
Why is tunnel ventilation specified as air speed instead of CFM per bird?+
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.
Is 32 °C dangerous for broilers, and how much air speed offsets it?+
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.
Does bird weight change the ventilation requirement?+
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.
What house cross-section should I enter?+
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.
What is a CFM and how does it relate to m³/h?+
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.
How accurate is this calculator?+
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.
Can I use this for layer or breeder houses?+
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.