Lumped-Parameter Models Comparison for Natural Ventilation Analyses in Buildings at Urban Scale

This study validates a three-zone lumped-parameter airflow model for Urban Building Energy Modeling, focusing on its accuracy in estimating air change rates caused by natural ventilation, referred to here as air change rate. The model incorporates urban-scale variables like canyon geometry and roughness elements for the accurate prediction of building infiltration, which is an important variable in building energy consumption. Air change rate predictions from the three-zone lumped-parameter model are compared against results from a three-zone CONTAM model across a range of weather scenarios. The study also examines the impact of building level of detail on air change rates. Results demonstrate that the three-zone lumped-parameter model achieves reasonable accuracy, with a maximum Mean Absolute Error of 0.1 h−1 in winter and 0.03 h−1 in summer compared to three-zone CONTAM model, while maintaining computational efficiency for urban-scale energy consumption simulations. However, its applicability is limited to buildings within urban canyons rather than detached structures, due to the assumptions made in the methodology of the three-zone lumped-parameter model. The results also showed that the model had lower errors for low to mid-rise buildings since the simplification of a detailed high-rise building into a three-zone model alters the buoyancy effect; a 4-story building showed Mean Absolute Percentage Error of 7% and 5% for a typical winter and summer day respectively when a detailed and simplified three-zone models are compared, while the error for a 16-story building were 18% and 12%. The results of building air change rates are used as input data in an hourly energy consumption model at urban scale and validated against measured hourly consumption to test the effect of the calculated urban-scale hourly air change rates.