  Citation: Curto, D.; Franzitta, V.; Guercio, A.; Martorana, P. FEM Analysis: A Review of the Most Common Thermal Bridges and Their Mitigation. Energies 2022, 15, 2318. https://doi.org/10.3390/en15072318 Academic Editor: José A. F. O. Correia Received: 25 February 2022 Accepted: 21 March 2022 Published: 22 March 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). energies Review FEM Analysis: A Review of the Most Common Thermal Bridges and Their Mitigation Domenico Curto , Vincenzo Franzitta , Andrea Guercio * and Pierluca Martorana Department of Engineering, University of Palermo, 90128 Palermo, Italy; domenico.curto@deim.unipa.it (D.C.); franzitta@dream.unipa.it (V.F.); pierluca.martorana@community.unipa.it (P.M.) * Correspondence: guercio@deim.unipa.it Abstract: The necessity to improve the energy saving potential of buildings is now a duty. European and national policies are being implemented to address the important decisions being made on this subject. For these reasons, several studies focus on this relevant topic. This paper review not only focusses on it but studies it in-depth. A commercial 3D simulation software was used to design a building sited in Palermo estimating the thermal losses before and after external envelope insulation. In particular, all the thermal bridges (TBs) were analysed with the finite element method (FEM) and mitigated with rock wool insulation. The paper shows the linear thermal transmittance difference and heat flux loss before and after TB mitigation. The results confirm the importance of installing an external insulation layer in the old building envelope. The linear thermal transmittance of TBs and the associated heat flux loss often decrease by more than 50%. Keywords: thermal bridges; thermal bridges mitigation; FEM analysis; building energy saving 1. Introduction Today, the topic of energy consumption in the civil sector is much discussed. In particular, research and actions are focused on trying to decrease heat losses in buildings [1]. Many action plans have been put into place, for example, in the European context we talk about the Energy Performance of Buildings Directive (EPBD), which promotes the improvement in the energy performance of buildings within the European Union, taking into account outdoor local and climatic conditions, as well as indoor climate and cost- effectiveness requirements [2]. European studies estimate that the energy consumption of public buildings accounts for approximately 10% of the total annual energy consumed in Europe [3]. In Italy, policymakers have put into place a recovery plan called “PNRR”, the “National Recovery and Resilience Plan” [4]. These economic support measures are aimed at reviving the country’s economy, which has been hit hard by the pandemic. Part of the allocated funds are intended for the restoration of residential and non-residential buildings. The citizens can deduct the costs of renovating their house under certain guidelines and financial ceilings. In this way, the aim is to reduce the thermal losses of buildings [5–7]. In this context, the proposed article will study the contribution of thermal bridges in the heat losses in a civil home located in Sicily, listing and studying them with the “FEM” analysis (Finite Element Method). In addition, a comparison will be made between the values obtained from the simulations and those tabulated in the national atlases of thermal bridges tabulated in the standard UNI EN ISO 14683 [8]. There are many studies in the literature on this subject, analysing its nature or its impact on the overall heat loss of a house; this is carried out by laboratory, numerical or FEM modelling studies. Davide Borelli et al. have implemented a bi-dimensional steady state FEM model to simulate the wall to floor thermal bridge. With the regression algorithm, the value of linear transmittance ψ has been carried out for a lot of different node configurations [9]. Seohoon Kim et al. have studied the heat loss coefficient of an envelope considering thermal bridges with the heat flow meter method. The result of the study shows that the Energies 2022, 15, 2318. https://doi.org/10.3390/en15072318 https://www.mdpi.com/journal/energies