Study of energy savings and environmental and economic impact of resilient cooling technologies in existing buildings

Ecosystems and the built environment are greatly impacted by climate change brought on by human activity. Due to its alterations, local extreme events occur more frequently and more severely, increasing their fatalities and economic costs. The Mediterranean area is particularly affected by heatwaves, which are extremely critical for health and productivity of people inside the dwellings as well as for energy consumptions related to cooling need. These events also increase the chance of power outages, which disable the operation of electrically powered cooling systems, raising the likelihood of indoor overheating. For these reasons, buildings play a crucial part in mitigating the effects of changing climate, in the optic of being resilient to new average conditions and extreme events. Resilience describes the ability of a system to withstand or recover from disruptions, taking advantage from its design and/or adopting appropriate strategies for returning to original conditions in a fast and efficient manner. This study investigated the resilience of different cooling technologies in the most common construction in Catalan building stock during present and future climatic conditions, heatwaves and power outages, evaluating also their impact on energy consumptions, environment and costs. The techniques implemented in the model include green roof, advanced solar shading, advanced glazing, natural ventilative cooling, vapor compression refrigeration and their combinations. Typical years and heatwaves for the city of Barcelona have been created for three time periods, Present, Mid Future and Long Future. They have been modelled using dynamical downscaled Regional Climate Models, climate projections based on IPCC scenarios. Power outages have been simulated during the most critical scenarios. Resilience was assessed using indicators that take into account climate resistance and thermal comfort. Climate resistance indicators consider the linear correlation between the grade of overheating inside a dwelling and the severity of outdoor conditions. Thermal comfort and survivability indicators evaluate sensations of building’s occupants related to several parameters, such as indoor air temperature, operative temperature and relative humidity. A potential scenario for future electric generation was simulated for evaluating the impact of passive measures in the reduction of primary energy use, carbon emissions and costs associated with the use of vapor compression refrigeration. The original building presented acceptable levels of climate resistance, while thermal comfort conditions resulted poor, especially during heatwaves. The application of the different cooling technologies significantly helped in the improvement of resilience of the dwelling. However, their performances reduced in the future scenarios, especially in the ones presenting severe outdoor conditions. Vapor compression refrigeration resulted the best solution for avoiding overheating inside the apartments, especially in case of heatwaves. Concurrently, natural ventilative cooling achieved good results in the improvement of climate resistance and comfort, as well as in the reduction of cooling and total energy needs of the building. Combinations of several passive measures resulted necessary for maintaining suitable conditions in case of power outages and reducing environmental impact and costs related to the use of vapor compression refrigeration, which confirmed the importance of the building envelope conditions.