Iovane, Teresa (2022) Energy efficiency of the building envelope: modeling, simulation and performance of passive-active technologies for double skin and responsive components. [Tesi di dottorato]

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Abstract

Climate change and its impacts represent the challenges of our day. Really, the climate has always changed in the history of our planet. However, the way in which it has been changing in recent decades puts us in front of a real climate crisis. Arctic sea ice reduction, sea level rise, intensification of extreme weather events, and global surface temperature rise are some of the contributing factors to the climate crisis. To date, it can be said that the anthropic greenhouse effect, which is caused by human activities, is responsible for these factors. The COVID-19 pandemic, the greatest shock of the last decades, has dispelled all doubts. The global electricity demand and the Global CO2 emission fell due to the restrictions adopted. Nevertheless, the past showed us that the rebound in emissions may be larger than the decline with the improvement of economic conditions. For this reason, it is necessary to think more to save energy, to have circular economy and to use sources with low environmental impacts. It is necessary to implement an energy transition by moving from an energy mix based on fossil fuels to one based on renewable energies in order to achieve the goal of decarbonization and climate neutrality. The construction sector, being energy-intensive, plays a key role in this context. To achieve the targets set at the European level, most of the built environment needs to be energetically redeveloped. Chapter 1 of this Thesis provides an excursus on the regulations adopted at International and European levels on environmental matters, highlighting the role played by the built environment and the consequent regulations issued in the field of energy efficiency in buildings. The focus of the Thesis concerns the analysis of strategies for improving the energy performance of existing buildings. To this end, the methods for the modeling and the simulation of the building energy performance are first described in Chapter 2 and then applied to different building types in Chapter 3. The complexity of these methods exposed first theoretically and then through examples has highlighted two aspects that have been discussed in Chapter 3. In detail, the influence of the effect of the urban context on the energy consumption of a single building is first investigated. The objective is to understand when and if it is possible to simplify the modeling phase while ensuring a high degree of reliability of the energy performance of the building obtained through dynamic simulation. Subsequently, it is proposed a novel, accurate but user-friendly tool for building modeling and energy simulation, called EMAR. This tool is aimed at professionals in the sector with the objective of simplifying the building modeling and characterization phase, carried out by defining only 63 inputs. This would avoid the use of simplified tools based on stationary/semi-stationary analyzes that compromise the accuracy of the results. Once the context and the methods necessary for the analysis of the energy performance of a building are known, technologies for the energy renewal of the existing building environment are investigated in Chapter 4. An effective way to reduce the energy consumption of buildings, while ensuring the comfort of the occupants, is the reduction of heat transfer and losses through the building envelope and therefore the reduction of heating/cooling loads. Attention was focused on the building envelope, as it is the primary subsystem through which energy losses between internal and external environments occur. In recent years, the concept of building envelope has undergone a transformation process: from a passive element, a protective barrier to a dynamic/adaptive element capable of varying its performance as the external environmental conditions vary and at the same time able to accommodate various types of plant engineering devices and equipment. In this context, the following topics have been addressed in Chapter 4: • a review and discussion of the most recent research on double skin facades and responsive elements for building retrofit; • the application of passive and active technologies based on double skin facades (DSF) for the energy retrofit of existing buildings with the analysis of the obtainable advantages. The aim of the review work is to identify recurring potentials and benefits related to the retrofit solutions discussed - such as reducing energy consumption and CO2-eq emissions, exploitation of renewables, and conceptual transformation of the building envelope - but also barriers and critical issues - as a risk of overheating, lower efficiency of transparent photovoltaics compared to traditional ones, high cost of reactive elements - which must be addressed and solved in the future. With this background, the use of double skin facades as a retrofit intervention for buildings typical of the Mediterranean area is proposed and investigated in terms of energy performance. A passive configuration is first analyzed. It consists of a second skin (entirely closed, without ventilation) that wraps the building, which is usually completely glazed. Secondly, to increase the energy advantages and reduce the problems of overheating in the cavity of the DSF, a system is proposed that makes the facade itself dynamic, by means of the controlled opening of the windows of the external layer. This active/dynamic configuration is described, and the energy benefits achieved through it are evaluated. Finally, a further aspect is discussed, which has recently become more significant in relation to energy renewal interventions. That is the importance of assessing the environmental impact of the materials used for energy renovation throughout their entire life cycle. The attention to this issue arises from a change in the relationship between the energy attributed to the operational and construction phases, following the increase in energy efficiency required by current regulations. The energy impact of different materials used for energy efficiency interventions for the building envelope, both opaque and transparent was then assessed, starting from the phase of extraction of the raw materials, to the realization of the product, to the implementation and use in the building.

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