Italian Residential Buildings Research Articles

Beta functions adaptation on empirical damage for a fragility model of Italian buildings

In this study, heuristic vulnerability model is presented providing damage distribution as a function of ground motion severity, through the use of given distribution function.Firstly, observational damage distribution are obtained from data collected after the recent earthquakes occurred in Italy and made available by DPC through Da.D.O. platform. The latter collect information on the main characteristics about building position, metrical data (e.g., number of storeys, interstorey height, storey area and construction age), structural types, severity and extension of observed damage on different building components. Moreover, the ground motion characterization was described via the ShakeMap published by the National Institute of Geophysics and Volcanology.Then, the two statistical models mostly used in the literature, i.e. binomial and beta, are used to determine the one most suitable to reproduce the observational damage distributions by means of godness-of-fit test. An introductive section properly examine the pro and cons in their use (number of parameters, flexibility). The observation of mean value and variance couple for more than 2000 damage samples obtained based on the considered database is used to obtain a general relationship which allows to reduce the number of parameters required by beta distribution, preserving its renomate flexibility.This enables the formulation of a novel heuristic vulnerability model for derivation of fragility curves. The model relies on the knoledge of mean damage trend with intensity measure and employs a probability distribution function. In this study, specifically, binomial and beta distributions are utilized. The generality of the method is then customized to suit the characteristics of Italian residential building stock, leveraging the information gathered after the 2009 L'Aquila Earthquake. This database presented an unprecedented opportunity due to the extensive data available on building geometrical and typological characteristics, seismic vulnerability, to the high level of representativeness of samples at municipality level, and to the thorough representation of damage patterns observed on building components.The fragility curves obtained through the presented vulnerability model are compared with those empirically derived from the observational data and are used to fully derive seismic risk scenario after 2009 L'Aquila Earthquake, in terms of economic losses, number of long term unusable buildings, the number of collapse, the number of deaths and severely injuries. The ensuing consequences deriving from the adoption of different fragility curves, i.e. empirical or with beta and binomial vulnerability models are deeply investigated.

Key Performance Indicators for Decision Support in Building Retrofit Planning: An Italian Case Study

To achieve climate and energy goals in the building sector, the current pace of renovating existing structures must double, overcoming prevailing barriers. Key Performance Indicators play a pivotal role in science-based decision making, emphasizing both direct and indirect benefits of building retrofits. The authors aim to contribute to proper metric identification for multi-perspective building performance assessment and formulate a methodology supporting energy planning decisions. They introduce the Global Cost per Emission Savings (GCES), an aggregated indicator encompassing both public (CO2 emissions) and private (global cost) perspectives of diverse retrofit technologies for building HVAC systems. Applied to the Italian residential building stock via the Reference Building approach, the methodology is tested using condensing gas boilers, biomass boilers, and electric heat pumps, revealing diverse environmental and economic performances. Addressing the establishment of effective decision-support tools for policymakers, the paper explores the potential impact of various policies on the favorability of technologies. Different policy scenarios are delineated to analyze how distinct approaches may influence the attractiveness of technologies. Notably, in the baseline scenario, biomass boilers hold an advantage over heat pumps according to the GCES index. However, scenarios involving technology-specific incentives or a greenhouse gases emission tax failed to alter the technological ranking, leaving heat pumps financially uncompetitive. In contrast, the TXPM scenario positions heat pumps as the most financially appealing option, penalizing biomass boilers for high particulate matter emissions.

The impact of the new EPBD “Green Houses” in the Italian building context: Technical-economic analysis on improving the energy class of existing buildings

The new European directive “Green Houses” aims at the decarbonization of the existing building stock. In this work, three building types widespread in Italy are analysed, virtually positioned in Palermo, Naples, and Milan. Considering that almost 60% of Italian residential buildings fall within the G and F energy classes, three energy retrofit measures are proposed (thermal insulation of vertical walls and roofs; replacement of the methane gas boiler for building heating and domestic hot water with a high temperature air-to-water heat pump; installation of a photovoltaic system), in order to reach at least D energy class based on Italian energy performance certification. A simulation-based approach is used. A declining tendency is noted in the normalized prices of the interventions when moving from detached house to terraced house and from terraced house to apartment in a tower building. Shifting from an independent to a centralized air conditioning system results in the same savings. Considering equal building features, hotter and milder climate zones reach higher energy classes; this also results in more difficult energy efficiency improvement in colder climates. Potential inequalities result from the implementation of the new European directive. Economic incentives to support the energy efficiency transition should be tailored to more specific conditions.

Simplified Multi-Life Cycle Assessment at the Urban Block Scale: GIS-Based Comparative Methodology for Evaluating Energy Efficiency Solutions

The Italian residential building stock consists of 12.2 million buildings, with 7.2 constructed post-World War II during the economic boom. These structures were designed without specific regulations for seismic safety, fire resistance, and energy efficiency, and today lies the current state of strong obsolescence. Therefore, energy refurbishment may not always be the best cost/benefit solution due to these intrinsic issues. Consequently, the transition to construction systems based on circular economy principles brings new opportunities and becomes key to proposing replacement interventions for this heritage. This paper presents a comparative GIS-based bottom-up approach to evaluate the lifecycle impact of residential building blocks, encompassing energy, environmental, and economic aspects. Two tools are introduced: one for measuring energy consumption and the other for quantifying the quantities of materials stored in buildings. This methodology permits comparing the new circular buildings and different refurbishment scenarios to identify the most suitable solution from an environmental impact and financial point of view. The application of a case study, a residential urban block in Bologna, built in 1945–1965, highlights how the demolition and reconstruction scenario based on circular economy principles presents the lowest environmental impacts and is economically competitive compared to standard deep renovation techniques.

Substitution of heating systems in the Italian buildings panorama and potential for energy, environmental and economic efficiency improvement

In many countries, old inefficient generators are used for heating purposes. A way to improve energy efficiency in those countries can be the choice of the most suitable heating generators to replace the current ones, without the inconveniences caused by other retrofit measures. In this context, we present a methodology to choose the most appropriate generator through dynamic simulations applied to building stock energy models. Economic, energetic, and environmental parameters guide the choice. The methodology is applied in the Italian residential building scenario, where the most widespread heating device is traditional boiler. Three options are considered: condensing boiler, heat pump, and hybrid heat pump (an alternative-working system with a condensing boiler and heat pump). For a detailed analysis, a white-box bottom-up building stock energy model is defined, through a statistical analysis, consisting of four building typologies in three different external climates. An hourly dynamic building-system simulation has been performed to obtain energy performance, emissions, and operational costs. The results have demonstrated that condensing boiler allows limited economic, environmental, and energy savings (8-14%), compared to traditional boiler. The highest economic savings are obtained with the hybrid heat pump (20%), while the heat pump alone leads to higher costs, but the highest savings in emissions and non-renewable primary energy (25-50%). The flexibility offered by the hybrid heat pump allows to obtain high savings in different cost scenarios, but also to further reduce CO2 emissions by implementing an environmental-based control strategy.

Energy performance gap of the Italian residential building stock: Parametric energy simulations for theoretical deviation assessment from standard conditions

Energy Performance Gap (EPG) is a crucial issue in the building sector that can lead to an overestimation of the national energy policies. It is the difference between the calculated energy consumption and actual energy use, and it is relevant mainly for space heating. As EPG quantification or correction methods could lead to more realistic energy policies, EPG has become a focus of many studies and research. In this framework, this study aims to quantify the theoretical deviation of EPG, i.e., concerning to the standard conditions, for the Italian residential building stock by performing parametric energy simulations of thousands of representative reference buildings. After a comprehensive thermophysical characterization of the national building stock, parametric simulations were carried out by varying the main standard conditions set in the Energy Performance Certificate (EPC) calculation. This approach allowed the quantification of EPG according to the climatic zone, building type, usage profile, and thermal insulation level of buildings, while also analysing the influence of these parameters on the EPG and checking for prebound or rebound effects (i.e. when standard consumption is greater or smaller than actual one). The study identified a range of EPG variability for both prebound (0% to +80%) and rebound (−30% to 0%) effects and quantified an average EPG between −3 and +16 kWh per heating degree day of the selected location as a function of the usage profile. This work represents the first attempt to calculate the EPG of the Italian residential building stock and it could lead to the correction of the national energy policies implemented in the building sector.

Whole building circularity indicator: A circular economy assessment framework for promoting circularity and sustainability in buildings and construction

Circularity is finding its feet in construction. Several Building Circularity Indicators (BCIs) have been developed to measure buildings' Circular Economy (CE) potential, but none of them has been standardized. Currently, the BCIs methodologies lack consensus on CE definition and scope, Key Performance Indicators (KPIs), and various other technical aspects. New research is hardly building upon the existing works and this lack of incrementalism hinders the standardization process. The current research addresses these limitations by developing a comprehensive and innovative Whole-Building Circularity Indicator (WBCI). WBCI consolidates the existing advancements by including the best features of various methodologies (like VBCI, MCI, Flex 4.0, etc.) and covering a wide range of KPIs. It has been developed from a life cycle perspective, taking into account all material flows from the point of origin to disposal or waste treatment. The adopted methodology complements popular sustainability tools like Life Cycle Assessment (LCA). The validation is done through a case study of a typical Italian residential building. WBCI along with an existing popular tool is applied to the case study using the actual building data to validate and highlight the improvements made in the developed framework. The building performed poorly in terms of circularity, scoring 0.243 on a scale of 0 (fully linear) to 1 (fully circular). It is found that resource-intensive construction processes and longer service life can substantially affect CE performance. Recommendations for improving the building circularity are given. From the methodological point of view, results emphasize that WBCI is a multilevel framework capable of identifying the best-performing CE solution at the material, element, system, and whole-building levels. Contractors, consultants, and policymakers may leverage WBCI's features to assess the circular performance of buildings at early stages. Researchers can also use the findings to further expand and standardize the BCIs.

Building energy consumption under occupants’ behavior uncertainty in pre and post-renovation scenarios: a case study in Italy

In Europe, the energy renovation of the existing building stock is a great opportunity to significantly reduce energy consumption and greenhouse gas (GHG) emissions and reach the European sustainability targets. In this framework, building energy simulations (BES) tools are very useful in verifying energy retrofit measures' effectiveness and compliance with national standards. However, an inaccurate numerical prediction, the so-called “performance gap” between measured and numerical performance, is often obtained, mainly due to the inherent uncertainty of model input. Due to its stochastic nature, the occupants’ behavior (OB) is considered among the key contributors to this gap. However, the most recent Building Energy Model (BEM) approaches adopt deterministic hourly-defined profiles for characterizing OB, thus neglecting the related uncertainty. In this work, the impact of OB uncertainties on energy consumption (EC) prediction is evaluated by adopting a Karhunen-Loève Expansion sampling technique, used to randomly perturb OB profiles such as heating setpoint (HS), internal thermal loads (IL), and windows opening (NV). Two BEMs of a typical Italian residential building in pre- and post-renovation scenarios are considered and calibrated on real EC data. The results demonstrated that HS uncertainty has the highest impact on EC in all scenarios. Moreover, the higher the energy performance of the building, the higher the impact of OB, especially for IL and NV patterns.

Generalised Storey Loss Functions for Seismic Loss Assessment of Italian Residential Buildings

ABSTRACT With a view to providing general Storey Loss Functions (SLFs) for existing reinforced concrete (RC) residential buildings in Italy, this paper layouts the procedure and the development of SLFs for different residential building typologies, using post-earthquake observational damage data of the 2009 L’Aquila earthquake. To do so, the addressed building typologies and the cost ratios, with respect to the total construction cost, for structural and non-structural elements were defined according to the Italian price bulletin of building typologies, using the current average construction cost per square meter. Fragility models available in the literature, which had been specifically calibrated for structural and non-structural elements commonly found in Italian and Mediterranean RC buildings, were employed and the assumed repair costs were the ones incurred for repairing the buildings damaged during the 2009 L’Aquila earthquake. The proposed SLFs were then employed to perform loss assessment on a representative portfolio of Italian existing masonry-infilled RC residential buildings, showing the consistency of the results with respect to available research studies. The outcomes therefore denote how the proposed SLFs can be a useful tool as an alternative to the simplified conservative loss assessment guidelines currently employed in Italy, with a view to planning risk mitigation measurements both at a regional and single-building level.

Effect of retrofit interventions on seismic fragility of Italian residential masonry buildings

In this paper, the vulnerability of ordinary unreinforced masonry (URM) buildings is analyzed, and the literature related to possible seismic retrofit interventions is reviewed in order to investigate their feasibility and effectiveness. These interventions are then simulated on a database of 445 buildings through Vulnus_4.0 software, that performs simplified mechanical analyses accounting for both global and local behavior of masonry buildings. The fragility of each building is assessed both in its as-built state and after the simulation of retrofit interventions. Fragility curves are then processed, and a fragility model for four building typologies is obtained for the as-built and the seismic retrofitted configurations. Lastly, mean damage maps are elaborated, and the performance of the proposed retrofit interventions is analyzed. The results of this work allow evaluating and comparing the improvement of seismic behavior brought by various retrofit interventions and could serve as a basis for further theoretical studies and for practical design in real cases.

Energy and Economic Savings Assessment of Energy Refurbishment Actions in Italian Residential Buildings: Comparison between Asset and Tailored Calculation

Residential buildings have become one of the leading sectors in the energy refurbishment process towards the clean energy transition. Energy Performance Certificates (EPCs), based on the asset rating calculation method, are often used to quantify the energy performance in standard conditions before and after renovation, but their energy outcomes can significantly differ from the actual energy consumption and savings. More consistent results can be obtained by adopting a “tailored” approach, capable of considering more the actual building operation conditions and users’ behaviour. In this framework, the study evaluates the heating energy needs of Italian representative multi-family houses in all the climatic zones and five retrofitting scenarios with both asset and tailored ratings. Finally, a cost–benefit analysis, based on energy savings and interventions costs, is also carried out to assess the affordability of the refurbishment actions depending on the adopted calculation methods. The analysis of retrofitting scenarios highlighted that asset energy outcomes are generally slightly greater than the tailored ones (differences of around 3–13% on average), but the affordability of the chosen energy efficiency measures is significantly overrated. It could underline the need to adopt the tailored approach for more accurate energy savings assessment and economic evaluation.

Effectiveness of seismic mitigation strategies for the Italian masonry building heritage

The seismic events that struck Italy in the last decades have highlighted the high seismic vulnerability of the built heritage. It is therefore of utmost importance to plan and prioritize mitigation strategies that can effectively reduce the amount of economic losses and the number of casualties produced by earthquakes.This work focuses on the definition of vulnerability for Italian residential masonry buildings. Fragility curves are elaborated for a database of 445 buildings through the software Vulnus 4.0, both for the as-built configuration and different intervention solutions. These vulnerability models are then combined with hazard and exposure data within the IRMA platform (Italian Risk MAps) to elaborate seismic risk maps for Italy, which show the possible losses for different return periods and time windows. By comparing the results provided by IRMA for the as-built configuration and the retrofit cases, it is possible to quantify the effectiveness of different mitigation strategies in terms of vulnerability reduction.

Clustering of empirical damage data for the vulnerability classification of the Italian residential building stock

This paper proposes an innovative data-driven vulnerability model for the classification of the existing residential building stock, by clustering observational damage data gathered after the 2009 L'Aquila earthquake. The proposed model preserves the conceptual framework at the basis of the macroseismic approach, which allows for a thorough vulnerability classification of the built environment by resorting to vulnerability classes and by accounting for the uncertain association of building typologies to vulnerability classes. Novel aspects of this study are the adoption of peak ground acceleration for the ground motion characterisation, which allows for overcoming possible limitations related to the use of macroseismic intensity, and the use of unsupervised machine learning techniques for removing subjectivity in the definition of vulnerability classes. A probabilistic framework is then set up allowing for the attribution of a given building typology to multiple vulnerability classes, based on an ad-hoc strategy, involving the use of probability theory and using empirically-derived typological fragility functions as a target. The use of a detailed post-earthquake survey form also allows for an improved definition of building types representative of the Italian building stock.

Fragility curves of Italian school buildings: derivation from L’Aquila 2009 earthquake damage via observational and heuristic approaches

Recent seismic events worldwide have demonstrated the high vulnerability of existing school buildings and the urgent need to have reliable tools for the rapid seismic performance assessment and damage and loss quantification. Indeed, the significant damage observed on structural and non-structural components may have a significant impact in terms of direct and indirect losses making critical the recovery of stricken communities. Although a significant amount of work has been done in developing fragility curves for the residential building stock, only few contributions clearly refer to school buildings that significantly differ in terms of the main characteristics from the residential ones. This research work proposes fragility curves for reinforced concrete and unreinforced masonry public school buildings typical of the Italian building stock, based on the damage observed in the aftermath of the 2009 L’Aquila earthquake. A comprehensive and unique database including data on damaged and undamaged school buildings (2037 records) in the Abruzzo region was built using data from four different sources. Due to limited amount of data, the fragility curves can be very sensitive to the method adopted for their derivation, thus three different approaches (i.e. empirical, empirical-binomial, heuristic) are considered in the paper and the results are compared. Finally, a direct comparison with fragility curves available in the literature for the Italian residential building stock is presented.

Modelling and Seismic Response Analysis of Italian Pre-Code and Low-Code Reinforced Concrete Buildings. Part II: Infilled Frames

ABSTRACT This study investigates the seismic response of archetype infilled reinforced concrete buildings representative of the existing Italian residential building stock by focusing on the modelling aspects of the existing infills, including their failure modes and interaction with the frame. The study compares the seismic response of the considered buildings, investigated through nonlinear static and dynamic analysis, with reference to two Performance Levels. The main variables considered are the construction period, the site hazard, the number of stories and the infill configuration. The observed return period capacity of the buildings mainly depends on the site hazard and on the construction period.

Estimating the Smart Readiness Indicator in the Italian Residential Building Stock in Different Scenarios

The Energy Performance of Buildings Directive 2018/844/EU introduced the smart readiness indicator (SRI) to provide a framework to evaluate and promote building smartness in Europe. In order to establish a methodological framework for the SRI calculation, two technical studies were launched, at the end of which a consolidated methodology to calculate the SRI of a building basing on a flexible and modular multicriteria assessment has been proposed. In this paper the authors applied the above-mentioned methodology to estimate the SRI of the Italian residential building stock in different scenarios. To this end, eight “smart building typologies”, representative of the Italian residential building stock, have been identified. For each smart building typology, the SRI was calculated in three scenarios: (a) base scenario (building stock as it is); (b) an “energy scenario” (simple energy retrofit) and (c) a “smart energy scenario” (energy retrofit from a smart perspective). It was therefore possible to estimate a national average SRI value of 5.0%, 15.7%, and 27.5% in the three above defined scenarios, respectively.

A computational framework for large-scale seismic simulations of residential building stock

Urban areas reveal particularly vulnerable due to the high concentration of people and, in many cases, their hazard-prone location. Indeed, according to data from the United Nations, about 2/3 of the population will live in large cities by 2050, and the majority of the world’s cities are highly exposed to disasters. This paper presents a computational framework to assess the seismic vulnerability and the damage of residential building portfolio in urban areas. First, a surrogated model is proposed to estimate the global capacity of building structures. Monte Carlo simulations are implemented to take into account the uncertainties associated with the material, mechanical, and geometrical parameters. The proposed approach is validated through nonlinear finite element models and a real case study. Then, the proposed computational framework is implemented and applied to a virtual city that is envisioned for being representative of a typical Italian residential building stock. The main achievement of this work is to introduce a new simplified approach for large scale structural analyses to limit the computational efforts while providing reasonable results.

Seismic fragility and vulnerability curves for the Italian residential building stock

In Italy, the recent regulatory and legislative developments relevant to the seismic risk mitigation of the existing building stock aim to propose tax deductions and simple but reliable approaches for the quantitative evaluation of the beneficial impacts of seismic retrofitting. Nevertheless, currently policy makers need tools and models able to assess the seismic risk and the cost/benefit of the strengthening interventions at regional/national level in order to plan future mitigation policies and be aware of the effectiveness of measures taken. To this aim, this article proposes a heuristic vulnerability model for large-scale applications. Starting from macroseismic approaches widely used in Europe, fragility and vulnerability curves for masonry and RC buildings are calibrated using a specific procedure based on the new Italian ‘guidelines for the seismic risk classification of constructions’ approved in January 2020, namely the so-called ‘Sisma Bonus.’ According to the construction material, building type and number of floors, the developed curves are defined in terms of vulnerability and height classes. The derived vulnerability model can be used in exposure models which rely on poor census data. Finally, it is compared with existing vulnerability models and the comparisons are analysed to demonstrate the effectiveness of the proposed model.

Comparative analysis of the fragility curves for Italian residential masonry and RC buildings

The Department of Civil Protection (DPC), in compliance with the EU decision 1313/2013 and at the request of the Sendai Framework for Disaster Risk Reduction 2015–2030 to update the disaster risk assessments by various countries, released the latest National Risk Assessment for Italy at the end of 2018. Specifically, as regards the seismic risk assessment, six research units belonging to two centres of competence of the DPC collaborated under its guidance to update the risk maps of the Italian residential heritage. This extensive collaboration complied with the recent Italian code for Civil Protection, which requires a broad scientific consensus for risk assessment. During this research activity, six fragility models were developed, according to some common criteria (four for masonry buildings and two for RC buildings). These models were then implemented by the DPC for the definition of the national seismic risk. Within this context, the aim of this paper is to evaluate the risk results provided by these models, compare their features, and assess and validate their prediction capabilities. In particular, this paper shows the comparison of predicted and observed damage scenarios and consequences on building stock and the population of two seismic events, i.e. L’Aquila 2009 and Amatrice 2016. Furthermore, the paper provides some interesting damage and risk predictions at a national level. Overall, the forecasts and comparisons made in this study demonstrate the validity of the approach adopted by the DPC for the assessment of national seismic risk.

Building heating demand vs climate: Deep insights to achieve a novel heating stress index and climatic stress curves

This study offers deep insights into the link between climatic stress and building heating performance. Two representative Italian residential buildings – existing and newly-built, respectively – are investigated by predicting heating demand for 63 locations, covering all typical national climates. Two simulation software are used – i.e., TERMUS® and EnergyPlus –, to compare a standard semi steady-state approach with a more accurate dynamic one. The comparison enables to understand the influence of the climatic stress on different levels of building modeling/simulation. Notably, the semi steady approach can provide reliable outcomes (close to the dynamic one) for existing buildings in cold climates. Then, a sensitivity analysis is conducted to investigate the correlation between climatic parameters and yearly heating demand, showing that the heating degree day index does not provide a complete explanation of such demand. Indeed, it does not take into account latitude and/or solar radiation, whose influence is not negligible. Therefore, a novel heating stress index is proposed, including normalized heating degree day and latitude. Its expression is optimized through a Pareto approach to ensure the best fitting/regression of yearly heating demand for both building typologies. The achieved determination coefficient (R2) is 0.990 for the existing building, 0.995 for the newly-built one. Finally, climatic stress curves are achieved to predict heating demand and related running cost as a function of the proposed index, providing a user-friendly but reliable tool to forecast building heating needs.