This paper discusses the revisions to ASHRAE Standard 55 regarding thermal comfort in naturally ventilated buildings. The new adaptive comfort standard (ACS) allows for warmer indoor temperatures in naturally ventilated buildings during summer and in warmer climates. The ACS is based on data from 21,000 sets of field studies in 160 buildings across four continents. The research shows that occupants of naturally ventilated buildings have a wider range of thermal comfort than those in mechanically ventilated buildings. The ACS is based on the analysis of thermal sensations, satisfaction, and acceptability, which are influenced by the match between occupants' expectations and actual indoor conditions. The ACS was incorporated into ASHRAE Standard 55, and it is now used for building design, operation, and evaluation. The paper also discusses the energy-saving potential of the ACS on a regional scale and new directions for research in building design and environmental control systems. The ACS is presented as an alternative to the traditional PMV-based comfort zone. The paper also discusses the importance of personal control in thermal comfort and the need for further research on inter-individual differences, climatic context, and the role of control in thermal comfort. The paper concludes that thermal comfort standards should move beyond neutral conditions to provide more pleasant and dynamic indoor environments.This paper discusses the revisions to ASHRAE Standard 55 regarding thermal comfort in naturally ventilated buildings. The new adaptive comfort standard (ACS) allows for warmer indoor temperatures in naturally ventilated buildings during summer and in warmer climates. The ACS is based on data from 21,000 sets of field studies in 160 buildings across four continents. The research shows that occupants of naturally ventilated buildings have a wider range of thermal comfort than those in mechanically ventilated buildings. The ACS is based on the analysis of thermal sensations, satisfaction, and acceptability, which are influenced by the match between occupants' expectations and actual indoor conditions. The ACS was incorporated into ASHRAE Standard 55, and it is now used for building design, operation, and evaluation. The paper also discusses the energy-saving potential of the ACS on a regional scale and new directions for research in building design and environmental control systems. The ACS is presented as an alternative to the traditional PMV-based comfort zone. The paper also discusses the importance of personal control in thermal comfort and the need for further research on inter-individual differences, climatic context, and the role of control in thermal comfort. The paper concludes that thermal comfort standards should move beyond neutral conditions to provide more pleasant and dynamic indoor environments.