This study considers indoor monitoring and building simulation to investigate the relationships between space standards (i.e., total floor area) and indoor environmental conditions in buildings. The research examines several occupied spaces within various buildings constructed with mass timber products. It explores monitoring and actual energy consumption data to validate the simulated results and includes thermal comfort surveys conducted during the field studies to assess occupants’ comfort and satisfaction. Indoor monitoring took place over several weeks during the summer months, coinciding with the generation and analysis of simulated results for the warm period. The study found stronger correlations between indoor and outdoor environmental conditions in spaces with smaller floor areas compared to larger ones. Elevated indoor environmental conditions were observed in spaces with smaller floor areas. Unlike larger spaces, these smaller areas require continuous cooling through natural ventilation or mechanical means during the summer, which increases overall energy costs in warm seasons. The research indicates that space standards are crucial for improving indoor environmental conditions and the overall well-being of occupants within the thermal environment. It is noted that occupants in smaller floor areas may interact with and use the controls more frequently than those in larger spaces. Furthermore, the study found that indoor environmental conditions, comfort, and space standards are interrelated. The research recommends that designers, planners, policymakers, building code experts, and stakeholders continually review the importance of space standards in the design of buildings and other facilities to enhance indoor environmental conditions, occupant comfort, and the overall well-being of users within the indoor thermal environment.