Improvement of thermal comfort for underground space: Data enhancement using variational autoencoder

The proportion of buildings occupying underground space has increased with three-dimensional urban development. Thermal comfort is crucial to the design of underground spaces and plays an important role in the optimization of building environment controls. Owing to limitations in recording various practical environmental parameters, it is difficult to access large data and further to establish an accurate forecasting model for the thermal comfort of an underground space. This paper addresses the problem from the perspective of data enhancement. A model for generating underground space data based on a variational autoencoder is proposed. The model maps data of the thermal comfort of an underground space to a highly compressed latent layer space and generates data in an unsupervised manner. The forecasting models were trained using the generated data, resulting in accuracy improvements of 41.34%-45.31%. Hence, the proposed generative model can learn effective real data features. The results also demonstrate that the adjustment of ventilation is more effective than the adjustment of the temperature and relative humidity in improving the thermal comfort of an underground space. The findings of this research will provide better thermal comfort evaluation for the operational management of building environment in underground spaces.