Guide · Ventilation design
Poultry house ventilation — minimum, transitional & tunnel CFM sizing.
Ventilation is the single biggest driver of bird welfare, FCR and mortality in a commercial poultry house. This vendor-neutral guide covers how to size minimum, transitional and tunnel ventilation, static-pressure targets, pad area and fan placement — so your RFQ can be benchmarked across manufacturers on identical CFM and static-pressure specs.
Design parameters
Minimum ventilation
0.10–0.20 CFM per lb bird weight — cold weather & young birds
Transitional ventilation
Timer + sidewall inlets, ~30–60% of tunnel capacity
Tunnel ventilation
Target air speed 2.5–3.0 m/s (500–600 fpm) at bird level
Design static pressure
0.10–0.15 in H₂O for tunnel; 0.03–0.05 for minimum vent
Cooling pad velocity
1.5–2.0 m/s across 6" pads; 1.0–1.5 m/s across 4" pads
Fan CFM rating basis
Rate at operating static pressure, not free-air CFM
Inlet area (min vent)
≈ 1 ft² per 1,000 CFM at 0.10 in H₂O
Emergency alarm threshold
±3 °C from set point or fan-failure detection
Reference bands used on commercial projects. Confirm against breed guide (Cobb, Ross, Hy-Line, Lohmann), local welfare rules and BESS Lab fan curves.
Ventilation modes
| Mode | When | Goal |
|---|---|---|
| Minimum (cold) | Brooding, cold season, night | Air quality only — remove NH₃, CO₂, moisture without chilling birds |
| Transitional | Mild weather, mid-grow | Bridge minimum → tunnel; sidewall inlets mix incoming air along ceiling |
| Tunnel | Hot weather, finishing | Wind-chill cooling via high air velocity end-to-end through the house |
| Tunnel + evaporative | Hot + dry weather | Add 6–11 °C of cooling through wetted pads at the inlet end |
Sizing workflow
- Confirm house dimensions (width × length × ceiling) from the layout guide
- Calculate peak heat load (birds × sensible heat × safety factor) and required air changes per minute
- Size tunnel fans at operating static pressure — not manufacturer free-air CFM
- Size cooling pad area from tunnel CFM ÷ target pad face velocity
- Specify minimum-ventilation fans + timer + sidewall inlet area separately
- Select climate controller with static-pressure sensor, alarms and generator changeover
- Issue an RFQ to multiple manufacturers on identical CFM, static-pressure and pad specs
Why the numbers matter
Under-sized fans, wrong static pressure or too little pad area translate directly into heat stress, mortality and FCR loss during the hottest weeks of the year — the same weeks that determine annual profit. Design tunnel ventilation for the design-day, not the average day.
Back to layout guideTurn ventilation specs into a comparable RFQ
FAQ
How many CFM do I need for my broiler house?
Peak tunnel CFM is set by target air speed (2.5–3.0 m/s) × house cross-sectional area, not by bird count. A 15 m × 3 m house needs ~90,000 CFM at ~2.7 m/s. Minimum ventilation is a separate calculation: 0.10–0.20 CFM per lb of live weight, sized for the coldest design day, not the peak flock.
What static pressure should I design for?
0.10–0.15 in H₂O for tunnel operation, 0.03–0.05 in H₂O for minimum ventilation. Always rate fan CFM at the operating static pressure — a fan advertised at 25,000 CFM free-air may deliver only 20,000 CFM at 0.10 in H₂O. Use manufacturer BESS Lab data where available.
How much cooling pad area do I need?
Pad area = tunnel CFM ÷ target pad face velocity. For 6" pads target 1.5–2.0 m/s (300–400 fpm); for 4" pads target 1.0–1.5 m/s. Under-sized pads increase static pressure, reduce fan CFM, and cause hot spots at the far end of the house.
When should I switch from minimum to tunnel ventilation?
Use minimum ventilation while outside temperatures are cooler than the target inside temperature. Use transitional (timer + sidewall inlets) as birds age and outside temperature rises. Switch to tunnel when you need wind-chill cooling — typically once outside temperature approaches bird comfort zone.
Do I need static pressure sensors and alarms?
Yes. Static pressure directly drives inlet air speed and pattern; without a sensor the controller cannot manage inlet position. Fan-failure and temperature alarms with independent power (battery + generator ATS) are standard on commercial houses.
How does ventilation link to the house layout?
House width and cross-section set peak tunnel CFM. House length caps how long the air can travel before it gets too warm (recommended max ~150 m without mid-house cooling). Orientation and fan placement follow the layout guide — fans at leeward end, pads at windward end.
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