Thermal insulation impact on overheating vulnerability reduction in Mediterranean dwellings

Heat waves are expected to increase the use of air conditioning (AC), deriving in higher energy consumption. This research aims to determine whether thermal insulation is an effective retrofit strategy for tackling overheating. Four occupied dwellings in southern Spain were monitored: two houses built prior to any thermal criteria and two with current thermal standards. Thermal comfort is assessed considering adaptive models and user patterns for the operation of AC and natural ventilation. Results show that a high level of insulation combined with a proper use of night-time natural ventilation can increase thermal comfort hours under heat waves, lasting 2–5 times longer than in poorly-insulated houses and with up to 2 °C temperature difference at nights. Long-term effectiveness of insulation under extreme heat presents a better thermal performance, especially in intermediate floors. Yet, the activation of AC usually occurs with indoor temperatures of 27–31 °C, regardless of the envelope’s solution.