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Nowadays, public buildings are clad on the outside, many with stone-clad facades. Energy requirements have changed a lot in the last 20–25 years, and the latest required value of the thermal conductivity of masonry is 0.24 W/m2K. The relevant requirements, available materials, and fastening technology options have changed significantly. Our research covers a comprehensive analysis of these systems, the selection of stone cladding materials, and the suitability and use of individual stone types for facade cladding, as well as an energy examination of layered wall systems and the development of fastening elements, including the material structure of the elements and possible design and fastening methods. In the original university research, we also developed an applied technology for several product manufacturing companies in order to obtain approval for industrial application. In this article, we summarize the results of our research, the building structure and building physics issues, the necessary fastening technology design, and the main aspects of selecting stone tiles regardless of the manufacturing companies. The goal of our university research was the introduction and structural development of assembled stone facade cladding in Hungary, a development that continues to this day. The assembled stone cladding system we developed has been used to cover the facades of thousands of buildings in Hungary.

The studied limestone is a well known Portuguese natural stone that occurs in Valverde—Alcanede region, located in the Maciço Calcário Estremenho (center of Portugal). This stone is used in several exterior and interior applications such as paving, cladding, masonry and decorations. Slabs made of the studied limestone were installed in ventilated facade with a “kerf” anchoring system in a building located in Valencia (Spain). After approximately five years, signs of degradation were detected on the facades through changes in color, enhancment of cracks and fissures that caused instability and collapse on several slabs. Limestone slabs comprise irregular patterns due to rock cutting across stylolites. These features represent ideal paths for fluid circulation through the slab and can be identified as vulnerability zones for exterior applications. Experimental procedure included several laboratory analyses to study clays and the iron oxide contents. Microscopic petrography, XRD and SEM observations were important to identify the interaction of the clay material in stylolites and fossil contours. Results show the importance of establishing standard methods for selecting stone on cladding applications. From the results, it is possible to understand that clay minerals have a strong influence on the mechanical performance of this stone. Among other important remarks, results show the importance of the development of standard procedures that acknowledge the structure and mineral composition before setting these natural products as construction materials. Proper stone selection was found important to avoid facade degradation, and hence contribute to prevent accidents and promote user safety as well as economic impacts.

The rationale for this work arose from the urgency of improving the energy efficiency of buildings at the design stage, given the changing requirements of energy efficiency standards such as the Polish Technical Conditions (WT 2014 and WT 2020). This research is novel as there is currently limited information available on the improvement of the thermal performance of ventilated stone facade systems, although they are now widely used due to their practical and aesthetic advantages. The first objective of this work is to evaluate the thermal performance of the ventilated facades of the Praski Student House (Akademik Praski) and to assess how certain design variations can help achieve a lower level of energy consumption. Using a comprehensive case study approach, this study provides accurate thermal calculations of the facade to assess its global thermal insulation coefficient (Rt) and thermal transmittance (Uc). The improvement in the actual U-value from the original design is as follows: the U-value is reduced from 0.33 originally to 0.228 for WT 2014 and to 0.198 for WT 2020, showing a reduction of about 30.9% and 13.2%, respectively. These results indicate the energy efficiency of increased insulation thickness and optimally oriented air gap dimensions. The practical contributions of this research are valuable for architects, engineers, and contractors involved in the design and construction process of buildings aiming to achieve near-zero energy buildings (nZEBs), including concrete suggestions on how to improve current construction practices as well as material recommendations. There is a need for durability studies, for example to assess the performance of such facades under different climatic conditions, as part of future work to support these findings.

Bowing is an uncommon pathology that can affect marble stone cladding of building façades, causing a large permanent deflection and the degradation of the flexural and anchoring strength of the stone slabs, which can lead to the cladding falling from the façades. Moreover, the combination of bowing with wind pressure effects on the building façades can increase the risk of fracture and collapse of the stone slabs, especially if this combination is not properly evaluated during design. Motivated by a case study, this work describes a stability evaluation of a 15-year-old building façade coated with marble stone cladding affected by bowing and subjected to wind pressures. This evaluation was focused on the stone slabs, and was performed through finite element model (FEM) numerical simulations of these slabs submitted to wind pressures and through lab tests using samples of stone slabs removed from the building façade. The results obtained demonstrated stability problems on the stone slabs caused by wind pressure-induced stresses combined with the loss of strength due to aging and bowing effects, especially for slabs with larger dimensions.

Façade claddings, as the outer protection layer of the building’s envelope, are directly exposed to environmental degradation agents. The façades’ orientation and their distance from the sea, among other location and protection-related factors, influence their vulnerability to climate loads, in particular wind and air humidity. These loads, as well as exposure to air pollution, affect the degradation process of claddings and the durability of façades. Therefore, studying the impact of the environmental exposure conditions on the service life of different external claddings provides useful information on their performance over time, which can support (i) decision-makers in the selection of the best façade cladding solutions and (ii) further research on the impact of climate change on building components. This study covers six types of cladding: rendered façades (R), natural stone cladding (NSC), ceramic tiling system (CTS), painted surfaces (PS), external thermal insulation composite systems (ETICS), and architectural concrete façades (ACF). Three hundred façades located in Portugal are analysed according to three main groups of variables, which characterize (i) the façades, (ii) their degradation condition, and (iii) the environmental deterioration loads and context. The statistical analysis results reveal that the environmental variables affect the cladding degradation process. South-oriented façades present lower degradation conditions than façades facing north. The distance from the sea and high exposure to pollutants add to the degradation conditions, reducing the expected service life of façades. The results reveal that claddings can be organized according to two main groups: the most durable (CTS, NSC, and ACF) and the least durable (R, PS, and ETICS) systems. This study enables a comprehensive analysis of the data, useful to draw conclusions about the influence of environmental exposure conditions on the degradation and service life of façade claddings.

Façades, as the most external building envelope component, are subject to different ex-ternal environmental loads, such as: Temperature, precipitation, damp, and wind. Therefore, the contribution of environmental actions to the occurrence of defects in façades claddings is an important subject of study since these actions strongly affect the degradation process and natural ageing of these components during their service life. In this study, a methodology to support decision-makers in the process of selecting a façade cladding system and the maintenance strategy to implement is presented and discussed. This methodology covers the performance of four façade claddings (ceramic tiling systems (CTS), natural stone claddings (NSC), external thermal insulation composite systems (ETICS), and architectural concrete façades (ACF)) over time, according to three environmental exposure variables (exposure to damp, distance from the sea, and orientation). The databases were established based on the diagnosis of the degradation condition of these claddings in-service conditions, in Portugal. The results reveal that the environmental exposure variables have a significant impact on maintenance requirements and costs. For all the categories of the environmental exposure condition variables, under all scenarios, ETICS is the least favorable constructive solution while CTS is the most advantageous solution. Furthermore, the results show that properly implemented maintenance activities enhance the performance level of building components, which positively affects their degradation behavior over time.

The efficiency of the inspection and maintenance of the buildings’ envelope is strongly linked to the means of access available to carry out these interventions. The adoption of adequate means of access facilitates the maintenance works, considering the constraints of each building. The means of access, besides having a fundamental role on the quality of the maintenance interventions on facades, represent a very significant part of the cost of repair of these elements. Therefore, the assessment of the cost variation between the different means of access available is fundamental to optimize costs and resources. In façades, there is a variety of solutions in terms of means of access. The selection of the most appropriate solution must be made according to the characteristics (e.g. architecture, height) and constraints (e.g. users, surrounding space) of each building, the needs for maintaining the façade, and the time and funds available for the intervention. In this study, a comparative analysis of the cost of the means of access in the maintenance plans developed for the different types of façade cladding (ceramic tiling systems, natural stone claddings, rendered façades, painted surfaces, ETICS, and architectural concrete façades) is carried out. The results show that the means of access costs influence the cumulative average maintenance costs and, in the longterm, there are advantages in planning permanent means of access at the design phase of the building.

The insurance market deliberately excludes the buildings’ envelope from their insurance policies, neglecting all the damage that can be caused by the degradation process or ageing of the materials. This stance is mainly due to the lack of knowledge in terms of risk and costs associated to the failure of these elements. Even though the building and its elements are the most valuable asset of any owner, most often homeowners do not adopt effective preventive measures to mitigate the deterioration and obsolescence of their assets. This study proposes an innovative methodology for the design of insurance policies for buildings’ envelopes, applied to natural stone facade claddings. The insurance product is defined based on deterministic and stochastic service life prediction models, established through the past degradation history of 142 natural stone claddings analyzed in service conditions in Portugal. Single-parameter (only analyzing the cladding’s age) and multiparameter (encompassing the relevant variables) models are applied in the calculation of the insurance premium. The expected claims are related with the performance of maintenance actions and established according to three degradation levels. The results obtained reveal that an increased knowledge about the insured cladding leads to a reduction of the risk margin and consequently, to a lower annual value of commercial premium paid by a household. This study proposes an innovative solution for tailoring the insurance products, in terms of the risk of failure of the buildings components, as well as the financial charges related with the maintenance of these elements, channeling the risks to the market.

Accessibility to buildings’ envelope depends on efficient inspection and other maintenance actions of their components. When access to these components is not planned, special means of access are required to carry out the maintenance work. Means of access, besides having a fundamental role on the quality of maintenance works of building envelope components, also represents a considerable part of the maintenance costs. Thus, to optimize costs and resources in maintenance plans, assessment of the impact of the means of access on maintenance costs is crucial. For works in height, there are several alternative means of access. The choice of the most adequate solution is strongly linked to the characteristics (e.g., architecture, height) and constraints (e.g., users, surrounding space) of each building, the maintenance needs of the envelope, and the time and funds available for the intervention. Therefore, in this study, a sensitivity analysis to understand how the cost of means of access can influence the maintenance costs is carried out. Moreover, the optimisation of maintenance activities in façade claddings is also analysed. This study intends to assess whether it is advantageous to consider permanent means of access during the design phase or opt for temporary means of access. In a first stage, the impact of six temporary means of access (supported and suspended scaffolds; articulated booms; telescopic booms; scissor lifts; and rope access) on the maintenance plans developed for the six types of claddings (ceramic tiling systems—CTS, natural stone claddings—NSC, rendered façades—RF, painted surfaces—PS, external thermal insulation composite systems—ETICS, and architectural concrete façades—ACF) is examined. The impact is estimated through a stochastic maintenance model based on Petri nets. After that, a sensitivity analysis and a multi-criteria decision analysis are performed. Based on the results, general recommendations are presented concerning the maintenance strategies to adopt in the cladding solutions analysed. The results reveal that planning the means of access during the design stage can be economically beneficial for all buildings’ envelope components.

In this study, the time-dependent stochastic degradation of three types of claddings is analysed. For this purpose, 203 façades with stone claddings (directly adhered to the substrate), 195 with adhered ceramic claddings and 220 with painted surfaces were analysed. All the façades are located in Lisbon, Portugal. Their degradation condition was assessed through an extensive field work. Based on the data gathered, Markov chains are used to predict the degradation of claddings and to understand, in some detail, how the characteristics of the claddings contribute to the overall degradation. The results show that the distance from the sea and exposure to damp are significant to the degradation of all types of cladding. The type and size of stone plates also influence the degradation of stone claddings. The exposure to wind-rain action has a high impact on the degradation of ceramic claddings. The models proposed provide useful information on the probability of failure of the claddings; these results are fundamental in the context of insurance policies and in the definition of building maintenance plans.