Guest satisfaction is pivotal for the hospitality industry, yet the role of Indoor Environmental Quality (IEQ) in shaping guest ratings remains inadequately explored. This study addresses this gap by leveraging web-mining, natural language processing and the Three-Factor Theory to analyse guest reviews of Australian hotels and serviced apartments listed on Booking.com. Findings indicate that most IEQ factors—thermal comfort, indoor air quality, luminous environment, acoustics, space, facilities, cleanliness, and layout—function as Basic Factors. While deficiencies in these areas drive dissatisfaction, their adequacy alone does not significantly enhance satisfaction. Notably, exterior view serves as an Excitement Factor in budget accommodations (three stars or below) but transitions to a Basic Factor in luxury settings. Among all IEQ factors, cleanliness, indoor air quality, and acoustics had the strongest negative impacts when underperforming, whereas satisfactory exterior views, cleanliness, and available space positively influenced guest ratings. The COVID-19 pandemic intensified these effects, heightening guest sensitivity to IEQ deficiencies (e.g., poor air quality) while elevating expectations for high-performing attributes like exterior views and available space. Overall, IEQ factors accounted for 32.8% of customer ratings in budget hotels and 23.9% in luxury accommodations. The findings underscore the necessity of ensuring satisfactory performance across all IEQ factors, particularly cleanliness and indoor air quality, while strategically enhancing exterior views and spatial configuration to optimize guest satisfaction. These insights provide hospitality managers and policymakers with data-driven guidance for enhancing guest satisfaction and operational resilience in post-pandemic hospitality settings.