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
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.
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.
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.
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.
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.
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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