Are simple models for natural ventilation suitable for shelter design?

Many competing airflow models are available to aid designers size windows for natural ventilation, but their complexity in terms of computation and the required expertise needed has limited their application in shelter design. Shelters house over 8 million people worldwide, and the prevalent inadequacy of indoor air quality exacerbates health risks. This study examines the use of simplified airflow models to guide the shelter design process to deliver adequate natural ventilation schemes and window dimensions. The classic Warren equations for natural ventilation are compared with airflow network models in Contam and EnergyPlus to contrast design outcomes from a practical perspective. Five natural ventilation mechanisms are tested across a representative single-zone shelter, based on those at Hitsats refugee camp (northern Ethiopia), using indoor CO₂ concentrations as the key performance indicator. Results for opening sizes and ventilation layouts derived from Warren are in close agreement with those from airflow network models in Contam and EnergyPlus. Wind-driven scenarios feature the same window size for 99% of the time, while buoyancy-driven scenarios are for 94–97% of the time. These results prove that simplified modelling approaches would lead to the same design decisions as more complex models, making them as suitable and as reliable for the design of single-zone shelters.

Policy relevance

This study illustrates the practicality of using simplified airflow models, particularly the Warren model, for designing natural ventilation in shelters within resource-constrained settings. The research shows that openings sized with the Warren model effectively maintain indoor CO₂ levels at < 1000 ppm in wind-driven scenarios, making it a reliable tool during the initial design stages. Although its performance is less consistent in buoyancy-driven scenarios, the model still offers valuable guidance, suggesting that some adjustments may be needed in these contexts. The study highlights that using simplified models can enhance the accessibility of natural ventilation design, especially in situations where advanced computational tools are not available. These findings underline the importance of simplified models in improving air quality in shelters, ensuring that design decisions are both practical and scientifically informed.