Moisture in buildings is a complex issue involving vapor pressure, relative humidity, and the thermal aspects of building materials. Therefore, the climate, the construction system and the layout design of dwellings have a significant influence on mold growth. This study investigates indoor humidity issues in wood frame social housing units located in Sao Sebastiao, Brazil, a coastal city characterized by mild temperatures along the year and rainy summer. Residents reported persistent moisture odors and localized mold growth, raising concerns about indoor air quality and habitability, even though the housing complex has been recently built. Temperature and relative humidity measurements were taken over a 7-day period during the spring season, to identify the environmental factors contributing to these issues. The building’s construction details, ventilation patterns, and surrounding climate data were also analyzed. The visual inspections and material sampling focused on areas prone to mold growth. Additionally, thermal and hygrothermal simulations were used to model moisture dynamics within the building envelope, identifying key factors such as inadequate ventilation rate, and insufficient moisture control. The study provided guidelines for improving the performance of wood frame social housing units in tropical climates, emphasizing the importance of preventive measures and regular maintenance to ensure healthy indoor environments. The findings intend to give a basis for best practices in design and construction to mitigate humidity-related issues, reduce mold growth, and improve indoor air quality.