Evaluation of thermal comfort in mixed-mode office buildings in hot and semi-arid climates: a case study from Burkina Faso

• Thermal comfort assessed in mixed-mode offices in Burkina Faso. • Seasonal shifts in thermal neutrality and preferred temperatures found. • Adaptive behaviors and clothing insulation affect comfort perception. • Comfort differs between air-conditioned and naturally ventilated zones. • Results support climate-specific comfort models for hot dry region. The assessment of thermal comfort in mixed-mode office buildings located in hot dry climates remains insufficiently explored, particularly in West African contexts such as Burkina Faso, where no local comfort standards currently exist. This study aims to address thermal comfort conditions in office buildings in the warm semi-arid climate of Ouagadougou, by combining field measurements of indoor environmental parameters with thermal comfort surveys conducted across eight mixed-mode office buildings. The field protocol included simultaneous monitoring of indoor and outdoor conditions, along with more than 1,100 thermal comfort votes collected through structured questionnaires during hot, cold, and rainy seasons. The results indicate that occupants’ thermal sensation and preference differ significantly between Natural Ventilation (NV) and Air-Conditioned (AC) operation modes. Neutral temperatures, estimated using the Griffiths method, ranged between 26.0 °C and 30.3 °C, while preferred temperatures ranged between 26.8 °C and 30.2 °C. A strong adaptive behavior was observed among occupants, particularly under NV mode, where comfort persisted at higher operative temperatures. Compared to international standards, the adaptive models of ASHRAE 55 (80 % acceptability limits) and EN 16798-1 (Category III) were found to be applicable under NV conditions but underestimated comfort limits during AC operation with an average exceedance from 0.5 °C to 0.7 °C, particularly during the peak hot season. These findings suggest the need for a context-specific adjustment of comfort temperature ranges in mixed-mode buildings within hot and dry climates. However, further studies are necessary to validate these results and support the development of regionally appropriate standards.