Since the rapid spread of COVID-19 in late 2019, Fangcang shelter hospitals have become crucial components of urban healthcare facilities. However, there remains a lack of systematic research on the performance assessment of Fangcang shelter hospitals. This study evaluated the construction efficiency, facility allocation, and indoor environmental quality (IEQ) of 115 Fangcang shelter hospitals in Shanghai. Based on the Bidirectional Encoder Representations from Transformers (BERT) model, 51,040 social media reviews were processed to evaluate the prevalence of IEQ complaints. The results show that Fangcang shelter hospitals renovated from exhibition halls have the fastest median construction speed (58.2 bed/h), closely followed by office buildings (41.7 bed/h), while containers were the slowest (9.1 bed/h). Notably, there is a power function relationship between the bed capacity and construction speed (R2 = 0.81), indicating a scale effect. As for the indoor environment, toilet comfort issues comprise 31.2 % of the total complaints, followed by complaints about acoustics (22.8 %), hygiene (12.0 %), and thermal (11.2 %). Container-built Fangcang shelter hospitals face significant challenges to the acoustic (40 %) and thermal (15 %) environment, while renovated facilities encounter more problems with toilet facilities and privacy. We also found that the proportion of indoor air quality (IAQ) issues increases as the average bed area decreases across facilities renovated from factories, exhibition halls, and office buildings. These findings offer valuable insights into Fangcang shelter hospitals, which can be considered in future planning and spatial optimization of emergency shelters.