Can windcatcher's natural ventilation beat the chill? A view from heat loss and thermal discomfort
Miaomiao Liu, Salah Almazmumi, Pinlu Cao, Carlos Jimenez-Bescos, John Kaiser Calautit
Abstract
Windcatchers excel in low-energy ventilation and summer passive cooling in temperate climates. However, their winter use has been limited by significant ventilation heat loss and potential discomfort. Limited research has detailed windcatcher heat loss in cold climates through field studies. This study aims to discuss windcatchers’ applicability in low-temperature conditions, focusing on ventilation heat loss and thermal discomfort. Field experiments were conducted in Nottingham, UK, during an icy period. A 3D-printed prototype windcatcher and a test room were built and tested in such weather conditions. A validated Computational Fluid Dynamics (CFD) model against the field experimental data was employed to investigate the windcatcher performance for a typical-sized UK primary school classroom. The field experimental results indicate that the indoor airflow patterns are dynamic and continually change with varying external wind conditions. Using static boundary conditions to investigate the ventilation process is inadequate and may result in inaccurate predictions, given observed fluctuations and irregular patterns. In the CFD modelling, significant over-ventilation may occur in the classroom at external wind speeds of 3 m/s despite being previously described as “satisfactory”, “adequate”, or “sufficient” ventilation. At wind speeds of 3 m/s or higher, the over-ventilation can cause a minimum 941.4 W heat loss, adding 4.7 kWh heating load and £1.6 electricity cost for a typical-sized single classroom during a 5-h occupied period. The research findings highlighted that control strategies should be introduced to reduce over-ventilation. Integrating heat recovery or thermal storage can enhance winter thermal conditions.