# Ventilation Modeling of a Hen House with Outdoor Access

## TL;DR

This paper develops and validates a CFD model to improve ventilation in cage-free hen houses with outdoor access, aiming to enhance hen welfare and environmental control.

## Contribution

The study introduces a validated CFD model for cage-free hen houses with outdoor access, enabling optimized ventilation strategies.

## Key findings

- CFD simulations predicted airflow velocity with less than 50% error for three of four scenarios.
- Temperature predictions had less than 6% error across all scenarios.
- Plenum-based systems outperformed sidewall systems by up to 136.3 air changes per hour.

## Abstract

Cage-free environments with outdoor access offer an opportunity for precision flock management through optimal environmental control practices. However, outdoor access disrupts the integrity of the indoor environment, including the properly planned ventilation. We aimed to develop and validate a CFD model of a cage-free hen house with outdoor access by specifying the real-world conditions and then using mathematical principles of airflow and heat transfer to simulate ventilation performance, leveraging the previous efforts. Computational fluid dynamics models of four different ventilation scenarios have been developed for the Penn State Poultry Education and Research Center (PERC) research room, which features two exhaust fans, sidewall ventilation inlets, wire-meshed pens, outdoor access, and plenum inlets. The simulations of four ventilation scenarios accurately predict the measured air flow velocity with an error of less than 50% for three of the scenarios, and the simulations predict temperature with an error of less than 6% for all scenarios. With a validated research room ventilation model, we can further examine different ventilation strategies to identify those that provide suitable thermal environments with minimal disruptive air-flow patterns. We expect that knowledge of an improved ventilation strategy will help the egg industry improve the welfare of hens cost-effectively.

Outdoor access, often referred to as pop holes, is widely used to improve the production and welfare of hens. Such cage-free environments present an opportunity for precision flock management via best environmental control practices. However, outdoor access disrupts the integrity of the indoor environment, including properly planned ventilation. Moreover, complaints exist that hens do not use the holes to access the outdoor environment due to the strong incoming airflow through the outdoor access, as they behave as uncontrolled air inlets in a negative pressure ventilation system. As the egg industry transitions to cage-free systems, there is an urgent need for validated computational fluid dynamics (CFD) models to optimize ventilation strategies that balance animal welfare, environmental control, and production efficiency. We developed and validated CFD models of a cage-free hen house with outdoor access by specifying real-world conditions, including two exhaust fans, sidewall ventilation inlets, wire-meshed pens, outdoor access, and plenum inlets. The simulations of four ventilation scenarios predict the measured air flow velocity with an error of less than 50% for three of the scenarios, and the simulations predict temperature with an error of less than 6% for all scenarios. Plenum-based systems outperformed sidewall systems by up to 136.3 air changes per hour, while positive pressure ventilation effectively mitigated disruptions to outdoor access. We expect that knowledge of improved ventilation strategy will help the egg industry improve the welfare of hens cost-effectively.