Poultry House Ventilation Calculator

Tunnel ventilation is calculated purely from the house's cross-sectional area — width times ceiling height — multiplied by a target air speed, because the goal is achieving a specific wind-chill cooling airflow through that opening, not matching a heat load from the birds. Bird count and average weight only drive minimum and transitional ventilation, which are explicitly moisture- and weight-based calculations.

Each mode addresses a different seasonal problem: minimum ventilation in cold weather removes moisture and ammonia while conserving heat, transitional ventilation in mild weather adds fresh air with some cooling, and tunnel ventilation in hot weather prioritizes moving enough air to physically cool the birds through wind-chill effect. Running tunnel-level airflow in cold weather would waste enormous amounts of heating energy, while running only minimum ventilation on a hot day would let the house overheat.

It shows how many times per hour the ventilation system replaces the entire volume of air inside the house, calculated from the CFM rate and house volume. Industry guidance commonly targets 4 to 6 air exchanges per hour at minimum ventilation as a benchmark for adequate moisture and ammonia control without excessive heat loss in cold weather.

Tunnel mode targets a specific air speed across the entire house cross-section to achieve a cooling effect, which typically demands a much higher total CFM than the moisture-control minimum ventilation rate calculated from bird weight alone — especially in a wide or tall house. Dividing that larger CFM requirement by a single fan's rated capacity naturally calls for more fans running simultaneously during hot weather.