Hybrid ventilation in a nearly zero-energy building as a function of users' habits for better indoor air quality and thermal comfort in a warm climate

During the design stage of a detached house located in warm climate, passive strategies were integrated and a high-energy efficiency qualification was achieved in accordance with the Spanish Building Technical Code (CTE). During the execution phase, an elevated level of control was carried out to guarantee airtightness and thermal insulation quality according to the specifications of the project. A hybrid ventilation system was designed and installed as it was allowed under Spanish regulations for residential buildings, but as a legislative exception. The mechanical part of the hybrid ventilation system was deactivated by the owner due to his cultural perception that effective ventilation can only be achieved by opening windows. Consequently, with the operable aerators closed, ventilation relied solely on traditional Mediterranean airing habits, impacting both the indoor air change rate and subsequently, indoor air quality and thermal comfort. This research aims to assess whether satisfactory levels of thermal comfort and indoor air quality can be attained solely through these airing habits, thus questioning the necessity of active strategies to meet the indoor air change rate requirements. Thermal comfort and indoor air quality are evaluated based on indoor environmental data correlated with users' declared ventilation habits.