Understanding thermal comfort in vernacular dwellings in Alentejo, Portugal: A mixed-methods adaptive comfort approach

While a significant body of literature has been published on thermal comfort in dwellings, the particular challenge presented by vernacular dwellings in striking a balance between improving thermal comfort, energy savings, and heritage conservation has not been adequately investigated. The occupants' way of life, embodying regional cultural practices and traditional adaptive behaviours, and their unique thermal expectations, impact thermal comfort perception but are largely ignored in current comfort standards. This paper addresses this gap by evaluating the thermal comfort of vernacular dwellings in Alentejo, Portugal, based on the Portuguese contextadapted thermal comfort model (PTC). The work also attempts to assess the suitability of thermal comfort adaptive and steady-state methods by undertaking a comparative analysis with the PTC model results. Key findings include the broad summer thermal acceptability in the vernacular dwellings, exceeding that of regular dwellings and thermal comfort standards, and the significant winter underheating, which highlights that priority should be given to improving cold-related risks. The PTC model was found to accurately represent summer thermal comfort conditions in naturally-conditioned vernacular dwellings in Alentejo, albeit underestimating underheated hours and requiring nighttime and boundaries adjustments to improve its accuracy. The methods detailed under EN 16798 and REH (Regulamento dos Edificios de Habitacao/Regulation of Energy Performance of Residential Buildings) are deemed unfit to evaluate thermal comfort in vernacular dwellings, especially in summer.