Mastellone, Margherita
(2021)
Towards a decarbonized built environment: energy ratings and technologies for refurbishing the existing building stock.
[Tesi di dottorato]
| Item Type: |
Tesi di dottorato
|
| Resource language: |
English |
| Title: |
Towards a decarbonized built environment: energy ratings and technologies for refurbishing the existing building stock |
| Creators: |
| Creators | Email |
|---|
| Mastellone, Margherita | margherita.mastellone@unina.it |
|
| Date: |
8 November 2021 |
| Number of Pages: |
412 |
| Institution: |
Università degli Studi di Napoli Federico II |
| Department: |
Ingegneria Industriale |
| Dottorato: |
Ingegneria industriale |
| Ciclo di dottorato: |
34 |
| Coordinatore del Corso di dottorato: |
| nome | email |
|---|
| Grassi, Michele | michele.grassi@unina.it |
|
| Tutor: |
| nome | email |
|---|
| Ascione, Fabrizio | UNSPECIFIED |
|
| Date: |
8 November 2021 |
| Number of Pages: |
412 |
| Keywords: |
Energy refurbishment; passive and active strategies; existing building stock; building energy simulation |
| Settori scientifico-disciplinari del MIUR: |
Area 09 - Ingegneria industriale e dell'informazione > ING-IND/11 - Fisica tecnica ambientale |
[error in script]
[error in script]
| Date Deposited: |
09 Nov 2021 08:11 |
| Last Modified: |
28 Feb 2024 11:34 |
| URI: |
http://www.fedoa.unina.it/id/eprint/14343 |
Collection description
Climate change is one of the most discussed global issues in recent times. The main cause of global warming is anthropogenic activity, which risks irreversibly compromising the survival of our common earth and the future of next generations. Human actions affect the environment, and thus this earth, in several ways: water quality and quantity, increased pollution and greenhouse gas emissions, depletion of natural resources, urban and village overheating, global heating of both coastlines and backcountries. Although it is relatively recently that humanity is taking actions to counter global warming, this phenomenon has affected the earth for much longer. NASA's Goddard Institute has recorded an increase in the global average temperature of 1° C since 1880, with a gradual rise of 0.2° C every decade. But what does all this entail? A rapid change in the atmosphere, ocean, biosphere, and cryosphere. The rapid melting of glaciers and sea-level rise, extreme climatic events, and desertification of entire areas are increasingly frequent occurrences, and right before our eyes. We must act quickly, by introducing actions for each sector that affects global emissions, and thus transport, industry, and construction.
On a global scale, the building sector has a key role, being responsible for about the 36% of energy consumption and 39% of carbon dioxide emissions in 2018, with the largest share for residential buildings. At the same time, according to the Eurostat data, the building sector has the highest potential in achieving energy savings. Indeed, even if today the building sector has a high weight on global energy consumptions, the future trends are positive, due to the international actions and regulations proposed by the countries to reach the targets of more sustainable and low emissions buildings. During the last years, CO2 emissions have seen significant growth and the main cause is population growth and urbanization. For low-income and lower-middle income countries, urbanization is even more foreseen from now to 2050, with a consequent increase in greenhouse gas emissions. In the developed countries, besides the construction of new buildings, a big issue is the refurbishment of the existing ones, designed without considering their environmental impact. For these reasons, international standards and legislation are focused, not only on the optimization of the design of energy-efficient new buildings but mainly on the renovation of existing buildings especially considering the low renovation rate (around 1-3 %/year before the COVID-19 pandemic) of the building stock. Presently, at the EU level, the average turnover rate is around 0.6%.
The necessity of interventions on present building stock, to improve energy efficiency and cut down energy consumption, becomes incumbent and indispensable. Until the beginning of the third millennium, because of the inefficiencies of the building envelope and the related high thermal dispersions, the most diffused way of intervention on existing buildings was simply excessive and inappropriate use of facilities, to balance the heat losses, getting an excessive increase of energy consumption and climate change emissions. By considering the European context, the very inefficient buildings of European cities, and thus the ones built quickly and without attention to thermal and energy performances (from the fifties to the seventies), already have been often interested by deep refurbishments promoted and funded starting by the Energy Performance of Building Directives. This is true mainly for cold countries. For the future, the new challenge, as it was established also by Directive 844/2018, will be focused on the improvements of thermal resilience and energy behaviors of recent buildings, the ones built around the 1990s and 2000s, often characterized by high energy demands for cooling, sometimes due to the indoor overheating related to excessive use of thermal insulation and no attention to passive mitigation strategies. This phenomenon, by also considering the pressing climate change, the condensation heat of air conditioning systems, the urban heat islands, is more and more actual. The development of new solutions and new interventions technologies in the building field is becoming necessary, with particular attention to the reduction of cooling demand.
This Thesis will lead us through a path on the energy efficiency of buildings, which starting from an overview of the current European and Italian legislative framework, will focus on traditional and innovative strategies for the improvement of the energy performance of existing buildings. With an innovative approach, the energy refurbishment of the built environment will be centered on the three levers of energy efficiency: the thermophysics of the transparent and opaque envelope, the systems for the microclimate control, and the energy conversion from renewable energy sources. To consolidated methodologies, innovative ones are coupled for the energy audit of real building case studies, public and private, with several uses, including residential or educational.
The Thesis is based on published studies developed within the research group and these are reported in the list of publications at the end of the manuscript.
The evaluation of building energy efficiency can be performed according to two different approaches, as recurrent in the available scientific literature: a) a numerical approach based on the implementation of a mathematical model, in many cases, in a simulation environment; and b) the experimental approach based on a controlled or real environment. For a complete knowledge of the building, the methods can be combined themselves to perform more detailed and accurate energy analysis. Both methodologies, widely described in CHAPTER 2, were employed in this Thesis, to characterize and analyze several case studies and the possible energy retrofit interventions.
The numerical approaches used to evaluate the building energy performances were mainly two: The Building Energy Simulation (BES) and the Computational Fluid Dynamic (CFD) analysis, that were also coupled to evaluate both the building energy consumption and its indoor environmental quality. Indeed, a BES is a time-dependent simulation, based on energy balances in a continuous thermal transient regime, performed by assuming sub-hourly time-steps and by resolving transfer functions. On the other hand, in a fixed temporary moment, a CFD simulation concurs to understand the kinetic fields of an indoor environment, the spatial trends of each parameter that define the indoor microclimate (e.g. temperature and air velocity), the thermal-hygrometric comfort, and the indoor air quality (IAQ).
Starting from real building case studies, this research work was not limited to the evaluation of the building energy performances through the cited approaches, but accurate environmental and economic analyses were performed to estimate the impact of proposed energy retrofit interventions. Cost-optimal solutions with related global costs, investment costs, payback periods of the invested capital, and economic indexes under a macro-economic analysis were calculated for a complete evaluation of the building energy retrofits.
But how do you intervene on a building for an energy refurbishment? Usually, all “levers” (i.e., building envelopes, active energy systems, renewables) for energy efficiency must be pressed, consecutively, to reduce firstly the heat gains, then the energy demands, and finally by allowing clean energy using renewable sources. This Thesis has examined, on real case studies, passive and active strategies singularly, respectively in CHAPTER 1 and CHAPTER 4, and in CHAPTER 5 interventions on all three levers of energy efficiency were accurately proposed and evaluated. Specifically, regarding the passive technologies for the building envelope, traditional and innovative cooling strategies were selected to reduce heat gains and minimize cooling loads for an educational building. Cooling strategies such as phase change materials, vented walls, cool and green roofs, are some of the technologies analyzed for the free or low-energy cooling of the building in CHAPTER 1. In the same chapter, a critical review of recent scientific investigations about green walls is reported. All parameters for the design optimization are discussed as well as the achievable social and private benefits, and all technical requirements of the green layers. The review points out “strengths”, “weaknesses”, “opportunities” and “threats” of this technology and highlights how benefits will acquire greater relevance considering the increase in global temperatures and the growing need to redevelop densely built urban centers.
However, intervening on the building envelope with passive strategies involves many benefits such as energy-saving and improvement of environmental comfort, but today, after the COVID-19 pandemic, it is almost unthinkable that an energy redevelopment does not also include intervention on the building technical systems. During the COVID-19 pandemic, the necessity of healthy and safe spaces has become prominent, and this means design effective mechanical ventilation systems to control the indoor air quality. Therefore, reduction of the building energy demand and the improvement of the livability and healthiness of spaces are equal priorities. CHAPTER 4 is entirely dedicated to the technological refurbishment of an Italian University building with the aims of improving the classrooms’ quality and safety, through a comprehensive approach for the retrofit design. The scope of this investigation is to do University classrooms safe and sustainable indoor places, during the SARS-CoV-2 global pandemic. Experimental studies (monitoring and investigations of the current energy performances) are followed by the coupling of different numerical methods of investigations, and thus BES, under transient conditions of heat transfer, and CFD simulations, to evidence criticalities and potentialities to designers involved in the project of indoor spaces hosting multiple persons. Both energy impacts, in terms of increase of energy demands due to higher mechanical ventilation, and indoor distribution of microclimatic parameters were investigated, by proposing new scenarios and evidencing the usefulness of HVAC systems, equipment, and suitability of some strategies for the air distribution systems compared to traditional ones.
In CHAPTER 5 energy refurbishments of the whole building/HVAC systems are proposed. Specifically, the theoretical assessment of the performance of applied energy retrofit and seismic enhancement measures for a student dormitory of the University of Athens is presented. Different interventions were applied: the whole reorganization of the building spaces, the improvement of the thermophysical properties of the building envelope, and the replacement of the systems for the microclimatic control. In addition, a critical analysis of several passive and active energy efficiency measures for three Italian residential buildings was conducted. The buildings, representative of the most recurrent Italian residential typologies, were simulated in different Italian cities, and so in different climates, employing both semi-stationary and transient approaches. Considering the energy, environmental and economic indicators, it was shown how the new Italian funding program can boost the diffusion of energy efficiency measures characterized by the best energy performance, and not by the best cost/benefit ratio.
Finally, by considering the high complexity required by common energy simulation tools in modeling and simulation, the last chapter (CHAPTER 6) proposes a novel, accurate but user-friendly tool for building modeling and energy simulation. It is called EMAR, and couple ENergyplus and MAtlab® and address Residential buildings. Only 63 numerical inputs are necessary to perform accurate energy simulations by generating a simplified building model, all completely under MATLAB environment. To use a tool like EMAR is not required any modeling expertise, drawings, or schemes of the energy systems, but only a few input parameters. The available outputs are numerous referring to energy and economic performance as well as thermal comfort. Thus, EMAR can be a precious tool to perform user-friendly but accurate building energy modeling and simulations.
Downloads per month over past year
Actions (login required)
 |
View Item |
