A new index based on Gini coefficient for evaluating the distribution uniformity of environmental parameters in buildings

The traditional coefficient of variation (CV) is the most commonly used index to evaluate the distribution uniformity of environmental parameters in buildings. However, there is no benchmark for the CV to judge how uniform the distribution of environmental parameter is. To address it, a new index based on Gini coefficient, i.e., revised Gini coefficient (Gini_rev) through the dimensionless normalization, was proposed to evaluate the distribution uniformity in this study. The indoor air velocity, temperature, and CO₂ concentration distribution in a commercial broiler building with cross and tunnel ventilation modes were obtained to demonstrate the Gini_rev. What is more, the evaluation effects of the traditional CV and proposed Gini_rev were compared, and the ventilation performances of the cross and tunnel ventilation modes were discussed. The results show that: (1) the maximums of the Gini_rev and CV were 0.604 and 2.105, respectively, which indicates that the Gini_rev can be ensured to be between 0 and 1 to provide a clear benchmark; (2) when assessing the uniformity of indoor air velocity, temperature, and CO₂ concentration simultaneously, the fluctuation ranges of the Gini_rev and CV were 0.084∼0.604 and 0.049∼2.105, respectively, which indicates that the Gini_rev can provide a unified comparison criterion; (3) the Gini_rev of the environmental parameters distribution with tunnel ventilation was larger than that with cross ventilation, reaching up to 36 % and 25 % for the air temperature and CO₂ concentration, respectively. The proposed Gini_rev in this study will help evaluate, design and control the indoor environment in buildings.