Dynamic Building Envelope Components and nearly Zero Energy Buildings: Theoretical and experimental analysis of concepts, systems and technologies for an adaptive building skin
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Due to the significant impact of the building sector on greenhouse gas emissions, newer and stricter regulations aimed at reducing total energy use in buildings have appeared in the last few years. In the European context, all the new constructions will thus soon be asked to be nearly Zero Energy Buildings (nZEB). In order to reach this target, new concepts and technologies capable of further improving buildings’ energy efficiency need to be developed. A very promising strategy to overcome current technology limitations is represented by revisiting the conventional approach that considers the building as a static object and moves towards the vision where the building is a responsive and dynamic system. The main feature of this concept is the possibility of continuously changing the interaction between the building elements and the outdoor/indoor environment in order to reduce the energy demands and enhance the exploitation of “environmental” and low-exergy energies. In this framework, the building skin is probably that element of the construction which shows the largest potential, especially if its properties can be continuously tuned so that the best response to different dynamic indoor and outdoor boundary conditions can be achieved. Although it is not possible to state that the dynamic building envelope alone could represent the only solution to achieving the nZEB target, great expectations are placed on advanced integrated façade systems. The aim of this research is therefore to evaluate to what extent dynamic and active building skins can reduce operational energy demand in buildings. In order to find an answer to such a wide (and general) question, the research activity is organized using a multi-level structure. Each segment of the investigation is thus dedicated to assessing the impact of such a vision on different scales: from a whole building skin approach (concept level) to an intermediate scale (system level) and further down to a very detailed and specific class of components (material-technology level). In the concept level, an ideal dynamic building skin is assumed and modelled. The performance of such a theoretical configuration is then numerically assessed and compared with that of a more conventional reference envelope solution. In the system level, an integrated multifunctional façade module, characterized by a high degree of adaptability and responsiveness, is presented, and its energy and thermo-physical behaviour evaluated by means of an experimental analysis. Finally, in the material-technology level, the implication of glazing systems integrating phase change materials on the energy performance and on thermal comfort are evaluated by means of experimental, numerical and laboratory analyses. The findings demonstrate that improvements in energy efficiency and comfort performance can be achieved when dynamic concepts, systems and technologies are applied. In every level, the dynamic component often provides a very good performance and, when compared to a conventional solution, advantages are shown. However, it is important that dynamic components are coherently employed in the framework of an integrated building design vision and properly managed. Further, the simple adoption of such systems without a global approach and optimal control strategies is often not enough to reach a significant improvement in energy efficiency and IEQ. The results also show that, sometimes, the advantages achieved by the investigated configurations may be lower than expected, though an optimization of their performance is probably still possible. Limitations in the analyses and possible solutions for future development of the research activity are also discussed, pointing out that, if from the one hand, considerable efforts are still needed in research and development before a completely adaptable building skin can be effectively employed on a large scale, on the other hand the large potentials that this vision has are worthy of further investigation.