This study investigates energy usage and thermal comfort in 116 innovative and mass custom prefabricated buildings. The case studies are residences of different prototypes in the western part of Europe. The buildings have average U-values of 0.12 W/mK2 (external walls), 0.17 W/mK2 (roofs), and 1.70 W/mK2 (windows). The study examined the performance of selected buildings from different orientations in summer and winter. The investigation addresses two research questions. (1) Can mass custom prefabricated buildings provide thermally comfortable indoor environment? (2) What about the energy assessment of the buildings compared to conventional buildings? The methodology includes thermal comfort surveys and post-occupancy evaluation (POE). Actual energy data were collected. The study analyzed over 218 questionnaires retrieved from the participants. The findings revealed the mean indoor temperatures ranged from 22.6 ℃–23.7 ℃ and 17.5 ℃–19.3 ℃ in summer and winter, respectively. The mean sensation is around the neutrality in winter while the respondents feel much warmer (4.5 out of 7.0) in summer. The neutral (Tn) and preferred (Tp) temperatures were 0.3 ℃ and 4.3 ℃ higher in winter than the values reported in summer. For the POE, higher thermal acceptability and satisfaction rates were noted in winter than the votes for summer. The mean annual gas usage varied from 10,496 kWh–12,114 kWh. The study recommends further research on energy assessments at the design phase of buildings. This approach will aid our understanding of various design interventions that can improve the overall performance of buildings.