Abstract
The envelope of buildings is subjected to external environmental actions, particularly those linked with hygrothermal actions, which could represent an important conditioning factor for their sustainability, especially due to the risks of the corresponding reduction of performance and durability. The conservation and renovation of heritage buildings is a multifaceted and intricate operation, which could entail a management approach that systematically connects the diverse valences and uses information technology required to perform the complex task of heritage building conservation.
An approach to the management and conservation of heritage buildings with the use of information technology is presented here, particularly with an initial description of the basic factors influencing moisture presence and surface recession/cracking in the vertical envelope of buildings and their respective impacts on durability. In the following, examples are presented of moisture presence and surface recession/cracking in the vertical envelope of buildings with natural stone (laterite) masonry walls and buildings with reinforced concrete elements and infill masonry walls. Subsequently, the presence of moisture in the vertical envelope of buildings and the consequent risk of water penetration, growth of organic materials and deposition of pollutants (salts) due to the impact of climate factors are analysed. Surface recession or cracking in masonry walls of the vertical envelope of buildings and the risk of their increase due to the impact of climate factors are evaluated. In the following, methods for the systematization of the analysis of the main anomalies of the vertical envelope of buildings and their causes are discussed. A general definition of the basic methodology for the systematization of the analysis of the risk of climate factors and anomalies in masonry walls of the vertical envelope of buildings and their causes is presented, aiming at the development of studies on the sustainability of buildings. Next, the systematization of climate factors with an impact on buildings is discussed as well as the systematization of the characteristics of masonry elements and of anomalies/causes in the building’s vertical envelope. Then, the prevention of the increase of cracking and moisture presence due to the impact of climate factors is discussed. Finally, important issues related to the quality of construction and management of the impact of environmental risks due to climate change in unreinforced masonry (URM) infill walls for minimizing their economic costs are presented.
Keywords
Introduction
The envelope of buildings is subjected to external environmental actions, particularly those linked with hygrothermal actions, which could represent an important conditioning factor for their sustainability, especially due to the risks of the corresponding reduction of performance and durability. Generally, the degradation process of infilled or resistant masonry walls of the building envelope is highly influenced by external agents of decay, the conditions of exposure and the intrinsic characteristics of the respective constituent materials. Moisture presence and surface recession or cracking of masonry walls of the building’s envelope could occur in particular due to hygrothermal actions mainly related to external temperature and humidity variations, as a result of water penetration, leading to a possible significant reduction of the safety and level of comfort and worsening of the aesthetic aspects of those buildings, especially detrimental in the case of heritage buildings.
Lately, buildings have been more exposed to altering conditions that modify and accelerate decay processes, which have been particularly intensified due to anthropogenic environmental impacts, as well as by the effects of climate change. Particularly, the effects of hygrothermal actions, which impair the performance of the building envelope of recent reinforced concrete (RC) buildings with infill walls or old buildings with resistant masonry, could be exacerbated by the predicted effects of climate change. The vulnerability of the heritage buildings could increase with these negative effects of climate change, due to adverse situations related to the increased risk of aggressive degradation agents acting on the building envelope and aggravating the processes of weathering that accelerate the decay of the elements of that envelope. The conservation and renovation of heritage buildings is a multifaceted and intricate operation, which could entail a management approach that systematically connects the diverse valences and the use of information technology (IT) required to perform the complex task of heritage building conservation. The preservation of cultural heritage has gradually incorporated IT to create building models in the data processes and diagnosis stages, on a multidisciplinary planning basis. Here, an approach to the management and conservation of heritage buildings with the use of IT is presented, particularly with a description of the basic factors influencing moisture presence and surface recession/cracking in the vertical envelope of buildings and their respective impacts on durability.
Research Aim
This study addresses the issue of systematization of the characteristics of masonry elements and of anomalies/causes in the building vertical envelope, aiming to develop an adequate approach to management and conservation of heritage buildings, with the use of IT.
Therefore, an approach to the management and conservation of heritage buildings with the use of IT is presented, particularly with an initial description of the basic factors influencing moisture presence and surface recession/cracking in the vertical envelope of buildings and their respective impacts on durability. In the following, examples are presented of moisture presence and surface recession/cracking in the vertical envelope of buildings with natural stone (laterite) masonry walls and buildings with RC elements and infill masonry walls. Subsequently, the presence of moisture in the vertical envelope of buildings and the consequent risk of water penetration, the growth of organic materials and the deposition of pollutants (salts) due to the impact of climate factors are analysed. Surface recession or cracking in masonry walls of the vertical envelope of buildings and the risk of their increase due to the impact of climate factors are evaluated. In the following, methods for the systematization of the analysis of the main anomalies of the vertical envelope of buildings and their causes are discussed. A general definition of the basic methodology for the systematization of the analysis of the risk of climate factors and anomalies in masonry walls of the vertical envelope of buildings and their causes is presented, aiming at the development of studies on the sustainability of buildings.
Next, the systematization of climate factors with an impact on buildings is discussed, as well as the systematization of the characteristics of masonry elements and of anomalies/causes in the building’s vertical envelope. Then, the prevention of the increase of cracking and moisture presence due to the impact of climate factors is discussed. Finally, important issues related to the quality of construction and the management of the impact of environmental risks due to climate change in URM infill walls for minimizing their economic costs are presented.
Materials and Methods
General
The preservation of cultural heritage has gradually incorporated IT to create building models in data processes and diagnosis stages, on a multidisciplinary planning basis (Moyano et al., 2022; Nieto-Julián et al., 2020). IT has been applied in conservation and renovation projects for heritage buildings, with the use of computers, telecommunication systems and other devices to create, process, store, retrieve and transmit information. The use of digitization methods, such as artificial intelligence and digital twin, is increasingly vital in improving heritage building conservation and renovation management and developing automated processes. These technologies are becoming very valuable in terms of improving the efficiency and precision of heritage building conservation and renovation.
The task of generating a geometric model as a catalogue of heritage buildings is vital in the process of conservation and renovation of buildings, where the metadata related to features of multidisciplinary planning are recorded.
Therefore, it is important to specifically address the application of IT in conservation and renovation projects for heritage buildings, and it is particularly important to implement and manage heritage building anomalies in IT platforms for the generation of heritage building models.
The conservation, consolidation and restoration of building heritage entail multidisciplinary actions, taking into account the intervention from integrity issues within the pertaining cultural context. The main goal of the study of heritage buildings is to appreciate their conception, construction techniques (also skills) and causes of their damage.
The operational process for conservation and renovation projects for heritage buildings is very complex, as it requires the consideration of multiple variables, from the documentary study and from geometric, mechanical, physical and chemical analyses, involving a systematic approach linking the diverse fields involved in the conservation of the heritage building.
Methodology for the Systematization of Analysis of the Main Anomalies of the Envelope of Buildings
The systematization of the analysis of the behaviour of masonry walls could require a definition of a suitable methodology based on the generation of a global system for the identification of anomalies and their presumed causes (CIB, 1993).
A generalized systematization of the inspection process based on the visual detection of anomalies, which targets in particular the standardization of the respective designations and terminology, requires supporting tools consisting of a classification list of anomalies, regardless of whether they are old buildings or recent buildings of RC structure, that establish the main categories of anomalies and their causes. The survey inspection could involve the examination of the anomalies and their qualitative analysis, aiming to promote adequate testing, for the analysis of their most probable causes (diagnostic tests) and the selection of suitable repair solutions.
Furthermore, it could also serve the purpose of the possible development of digital models to help the survey of construction anomalies and decision-making processes subsequent to that survey (Francisco et al., 2020). Digital models to be used in a decision-making process could be a useful approach in the operations of conservation and maintenance of buildings (Seo et al., 2022). For example, classification systems could be eventually studied to assess their potential integration in digital solutions further, to resolve problems of conservation and maintenance of buildings, to supply a valuable contribution to get real-time monitoring of buildings and connected activities and to refine decision-making, in terms that it could deliver sound-based decisions. Buildings can use real-time data and models to analyse and minimize cracking and moisture in the building envelope and reduce the negative impact of environmental effects on buildings (Francisco et al., 2020).
A digital-based assessment framework could possibly be developed for evaluating the energy-saving strategies in buildings (Seo et al., 2022), which could involve the construction of a digital model that simulates the transfer of moisture in the building envelope, targeting to find the preventive measures to be implemented. It could be useful to associate an archive of the images of construction anomalies and recognize their main patterns through digital processing of the images and extraction of characteristics.
Therefore, it is justified to develop a basic methodology for the analysis of the risk of climate factors and of anomalies and their causes in masonry walls of the vertical envelope of buildings.
Anomalies Related to the Presence of Moisture and Cracking or Surface Recession or Cracking in Masonry Walls of the Vertical Envelope of Buildings
Anomalies related to the presence of moisture and cracking or surface recession or cracking in masonry walls of the vertical envelope of buildings due to hygrothermal actions could have a detrimental impact on their performance, likely severely reducing the safety and level of comfort of the buildings and worsening the aesthetic aspect of their façades. Moreover, alterations in the preservation conditions of buildings due to climate-related decay processes are inevitable phenomena. The knowledge of the mechanisms governing these processes could permit the prediction of their behaviour earlier and allow the development of opportune preventive conservation and possible restoration.
Old buildings with resistant masonry walls could present cracking and moisture, which depends on the type of masonry wall: stone masonry, brick masonry, etc. The assessment of the performance of old buildings particularly in relation to the occurrence of anomalies related to moisture and surface recession (also called surface erosion) or cracking needs specific knowledge, especially in the case of heritage buildings, due to the multidisciplinary character study of the type of buildings which cover an increasing degree of skills and of specialties, required to develop an adequate diagnosis of the causes of the anomalies related to cracking and moisture presence, especially considering the preview effects of climate change. The main anomalies that occur in brick masonry are related to cracking or water action–related phenomenon. It is stressed that these two phenomena are not independent, and each of them may cause or worsen the other.
Regarding the buildings with RC structures, besides the exposition to normal actions of their envelope based on infill masonry walls, added environmental actions from climate changes could increase the probability of defects in RC elements most commonly related to their cracking related to reinforcement corrosion (carbonation of the passive layer of the reinforcement), alkali–silica reaction and salt crystallization. The most relevant durability problems in RC structures are essentially related to the corrosion induced by chlorides and by carbonation (in case the carbonation front progresses until the surface of the reinforcement is reached, the passive layer of the steel surface will be dissolved, and the process of corrosion of the reinforcement may begin).
Cracking can have a particularly negative effect on the mechanical resistance in masonry walls, and the humidity could be an aggressive agent for building envelope performance.
Basic Factors of Influence of Moisture Presence and Surface Recession/Cracking in the Vertical Envelope of Buildings and the Respective Impact on Their Durability
The basic factors of influence of moisture presence and surface recession/cracking in the masonry walls’ vertical envelope of buildings and the respective impact on their durability in the envelope of buildings could be essentially the following: temperature variations, wind-driven rain (WDR), relative humidity and variations in air pollution.
Generally, the moisture present in wall renders could be related to the following factors: WDR incident in the walls, hygroscopicity of materials, construction moisture and rising damp. These factors are detailed in the following.
Precipitation accompanied by intense wind (WDR) is the principal agent accountable for the wetting of building envelopes. Degradation of a building’s vertical envelope due to cracking of the URM infill wall (associated, e.g., with temperature and moisture cyclic variations) could modify the permeability of these external surfaces to the rain with a horizontal velocity component given by the wind. A WDR incident in the wall could allow the penetration of rainwater through the cracking and masonry joints (Erkal et al., 2012; Pérez-Bella et al., 2013), besides the water present in the render by capillary action (moisture leading to the presence of stains, which could be progressively added by biological material growth, dirt deposition and salts (efflorescence due to salts) or chlorides).
In the context of building performance, hygroscopicity refers to the capacity of building materials to attract and retain water molecules from the air or other sources. This property can have both positive and negative effects on building performance. These hygroscopic materials are able to moderate indoor humidity levels and thus improve the thermal comfort and perceived air quality in buildings while still providing low energy consumption (Osanyintola et al., 2006). The impact of hygroscopic materials depends on many factors: the amount and type of materials in a given room, the outdoor climate, the outdoor ventilation rate and the moisture production rate, which also depends on the indoor temperature and RH (Osanyintola et al., 2006). The hygroscopicity of materials could lead to moisture stains and localized degradation of the render in zones associated with elevated concentrations of salts.
Condensation could originate from long-wave radiation on clear nights by attaining temperatures below the dew point of the air. The manifestation of microorganisms, generally in the northern parts of buildings, is influenced by the wetting mechanism associated with the occurrence of these condensations (Zillig et al., 2003). The biological growth of façades depends on the essential presence of humidity, related either to condensations or to wetting by WDR (Zillig et al., 2003).
Due to the crystallization mechanism of salts and its damaging effect on porous networks, sodium sulphate is especially considered to be a striking destructive agent in porous stones, concrete or brick weathering, and it is very relevant to the sodium sulphate decay and the salt crystallization pressure (Angeli et al., 2010).
About the rates of mass loss from calcareous (carbonate) stones, data of field exposure experiments were used in statistical analyses to propose cause-and-effect relationships with environmental variables, i.e. damage functions (Lipfert, 1989). The rates of damage (recommended type of respective estimation: ‘material lost per meter of precipitation’) could be affected by three mechanisms: calcite dissolution in “clean” rain, additional dissolution due to acidic precipitation, and loss by conversion to soluble salts as a result of dry deposition of SO2 or other acidic species (Lipfert, 1989).
Buildings exposed to outdoor pollution (especially located in densely urbanized zones heavily affected by atmospheric pollution) are subjected to the degradation phenomenon, including the formation on their surface of black crusts, causing inconvenient blackening and deterioration of the buildings, especially negative for the aesthetic aspect of heritage buildings (Comite, 2021).
Examples of Moisture Presence and Surface Recession/Cracking in the Vertical Envelope of Buildings with Natural Stone (Laterite) Masonry Walls and Buildings with RC Elements and Infill Masonry Wall
In the following are presented examples of moisture presence and surface recession or racking in the vertical envelope of buildings with natural stone (laterite) masonry walls and buildings with RC elements and infill masonry walls.
Relative to the buildings with natural stone (laterite) masonry walls, laterite characteristics and the way it can be used in the construction of buildings could explain their specific performance; hence, it is important to assess these detailed characteristics. Laterite is a rock/soil type rich in iron and aluminium, usually located under superficial soil layers, which was used long before in the form of natural stones (usually designated as ‘Laterite stone blocks’; see Figure 1(a)) in the construction of the envelope of buildings (including the façade of monuments), by cutting laterite into block-like shapes, and for masonry walls, which could be laid with or without joint mortar in the joints.
The conversion of laterite extracted from quarries or mines of lateritic crusts into laterite stone blocks could easily be made manually or with the machine-cut method, due to its common soft characteristics and the ability to be effortlessly broken into these shapes, although, in certain cases, it could exhibit very strong resistance properties and difficulties in cutting. Laterites could vary considerably, in terms of their properties, due to their location, which means much diverse values of the depth relative to the superficial soil layers, and due to different climates, but almost all laterites are rusty-red in colour, due to the referred high iron oxide content, and could usually be presented in the form of a highly compact and cemented soil. In the process of quarrying the laterite material into masonry when exposed to normal atmospheric conditions with gradual evaporation of inside moisture, it progressively gets hard and resistant. The strength resistance of laterite stone blocks could be related to the strength resistance of mortar aiming to estimate masonry strength resistance and elastic modulus of masonry, particularly considering a usual vertical compression resistance value of more than 2 MPa. To analyse the mechanical behaviour of those blocks, from the basic material properties available in literature, analytical models could be derived using them, as input parameters, for finite element analysis of laterite-confined masonry buildings under quasi-static loading (Chourasia & Singhal, 2023). Numerical studies were performed on LCM buildings (Chourasia & Singhal, 2023), showing the need to increase the wall thickness with the rise of the height of the building (wall thickness could commonly vary between 150 and 300 mm).
Masonry walls of laterite stone blocks exhibit interesting hygrothermal properties, which allow to keep a good level of thermal comfort of the inside spaces of the building (propitiating cool spaces).
In the following are presented the partial views of the masonry walls made with laterite stone blocks of a building façade (Figures 1 and 2), where the masonry wall façade is apparent/without the render (Figure 1(b)—a wall made of laterite stone blocks without the render) or with the render (Figure 2). The façade of the building in Figure 2 presents signs of moisture stains, cracking and detachment, in a natural stone (laterite) masonry wall; cracking and stains could presumably be due in part to hygrothermal actions.
(a) Aspect of Laterite Stone Blocks. (b) Partial Zone of a Masonry Wall of a Building Façade.
Partial View of a Masonry Wall of the Façade of a Building (Natural Stone—Laterite) with Moisture Stains, Cracking and Detachment, Presumably due in Part to Hygrothermal Actions.
The anomalies in these types of buildings with their masonry walls based on the natural stone of laterite could be related in certain cases to the presence of moisture and surface recession/cracking. The decay of masonry is highly influenced not only by aggressive environments but also by the choice and combination of constituents within masonry. Therefore, due to their constituent material, in a building’s masonry walls made of natural (laterite) stone, the vertical envelope is susceptible to cracking and moisture presence in that envelope, which could inconveniently significantly impair their performance and service life in the case of buildings, especially heritage buildings, which require added levels of the safety/comfort and aesthetic aspects of their façades and their inside spaces.
The study of moisture migration in the inner parts of the materials and construction building components is of high complexity (Dong et al., 2020; Qiu et al., 2003) and has a dominant relevance for the study and characterization of its behaviour, especially regarding their negative impact on waterproofing, degradation appearance, and thermal performance and durability of the envelope. Due to the reduction in the length of bricks, the vertical joints in the walls get closer, causing them to develop cracks. The reduction of adhesion/cohesion in the render of façades (erosion, pulverulence and detachment ) is often related to surface recession or cracking and the presence of moisture; meanwhile, on painted surfaces, the reduction of adhesion/cohesion could be associated with debonding and detachment in painted surfaces and their degradation can involve staining or colour change (usually in the beginning of the service life of applied painting) and chalking, which occurs subsequent to the reduction of gloss and leads to wear detachment and loss of material.
It can be seen in Figure 3 that the superficial zone of RC elements shows signs of degradation, and also the zone beneath the surface is subjected to an active process of degradation. It could be said that, in case the carbonation front progresses until the surface of the reinforcement is reached, the passive layer of the steel surface will be dissolved, and the process of corrosion of the reinforcement may begin.
Cracking and Local Detachment of Concrete and Corrosion of the Reinforcement Visible on RC Elements and on Infill Masonry Walls of Buildings with a Reinforced Concrete Structure. (a) Rust Formation and/or Loss in the Cross Section of the Rebars in the RC Element Associated with a Process of Corrosion with Localized Spalling or Delamination of the Concrete Cover. (b) Cracking and Detachment of Infill Masonry Walls.
It is recognized that the presence of water or moisture is the main factor that controls the diverse deterioration processes of the RC elements, apart from mechanical deterioration, and the transport of that water within the concrete is dependent, in particular, on the pore type (size and distribution) and on the existing cracking in the RC elements (
Moisture Presence in the Vertical Envelope of Buildings and the Consequent Risk of Water Penetration, Growing of Organic Materials and Deposition of Pollutants (Salts) due to the Impact of Climatic Factors
Precipitation accompanied by intense wind is the principal agent responsible for the wetting and decay of the building envelope. An increase in precipitation under climate change could lead to the saturation of soils and the overloading of gutters and downpipes and, hence, a higher risk of damp penetration in heritage building materials, including masonry walls (Sabbioni et al., 2009). The penetration of water into porous materials can also result from condensation as well as from capillary action, and water ingress leads to material degradation through corrosion, biological activities and subfluorescence due to salt crystallization (Sabbioni et al., 2009). The increase in precipitation and in the concentrations of atmospheric pollutants could upsurge the damage caused by the deposition of atmospheric pollutants such as SO2 and NOx, as well as increased atmospheric CO2 and increased concentrations of acid rain, which are directly connected to the corrosion of the material (Sesana et al., 2021). Corrosion is a chemical phenomenon that causes the gradual deterioration of materials by the action of water, usually together with salt (commonly chlorides) deposition, and is more prevalent in the presence of acid rain and higher atmospheric concentrations of carbon dioxide (CO2) for carbonate stones (Sabbioni et al., 2009). Biological growth creates different types of damage such as biomass accumulation, algae decay and lichen decay on stones, and this growth is associated with precipitation, humidity and temperature (Sesana et al., 2021). The microorganisms that participate essentially in the biodeterioration processes of inorganic materials are autotrophic and heterotrophic bacteria, fungi, algae and lichens.
The assessment of this damage could be based, in particular, considering the formation of microorganisms and the growth of biological materials, on the heritage building, and these two phenomena depend on the climatic conditions of the area, as well as the pH of the rain, the exposure to light and the physical characteristics of the material (Bertolin, 2019).
In terms of the damage to heritage buildings, the relative humidity could be considered another influential factor in parallel to the precipitation factor and is convenient to consider its long-term variation when assessing damage that occurred in the past and the damage expected under the effects of climate change.
To assess the predictable impact that environmental factors may have on heritage buildings, dose-response formulas have been developed, through damage quantification. Particularly, the impact of climate change on heritage buildings has been studies using dose-response formulas (Sabbioni et al., 2009), which normally include climatic variables, such as precipitation, temperature (maximum, minimum or average) and wind speed, as well as atmospheric pollution variables, such as the concentrations of SO2, HNO3 and H+ as a function of rain pH, to determine the deterioration of different materials. These dose-response formulas are defined using the relationship between the degradation of the material and degradation factors (e.g., environmental exposure).
Surface Recession or Cracking in Masonry Walls of the Vertical Envelope of Buildings and the Risk of Their Increase due to the Impact of Climatic Factors
The anomalies related to surface recession or cracking associated mainly with mechanical loads are analysed in the following, particularly those with a negative impact in terms of water penetration principally linked with WDR in masonry walls of the vertical envelope of buildings (Dias, 2023a). Moreover, cracking and associated water penetration could subsequently worsen their weathering properties and could undermine the structural building elements, reducing their mechanical resistance due to wetting and the associated progressive deterioration. Mechanical actions applied to the building envelope could induce deformations that may cause significant stress in masonry walls, which distress and could lead to an upsurge of cracking, as a consequence of axial forces (tension or compression) and applied shear forces. Normal or shear stress values greater than, respectively, the normal or shear strength of the material could generate the indispensable conditions for the formation of cracking. Cracking related to the effects of moisture or temperature variations, usually, is perceptible by specific signs, related mainly to shear effects (Dias, 2023b).
WDR with a horizontal velocity component is one of the main factors accountable for surface erosion (Erkal et al., 2012), which causes surface erosion of stone materials, collapse of and/or damage to buildings and archaeological structures, and wind abrasion (Sesana et al., 2021).
The intensity of rainfall and wind speed, together with temperature and relative humidity, could be important in contributing to the type of erosion of the material. This negative impact depends on the location of the building and the wind direction, which influences the penetration of rainwater and pollutants and particles in the atmosphere.
Results
General Definition of the Basic Methodology for the Systematization of the Analysis of the Risk of Climate Factors and Anomalies in Masonry Walls of the Vertical Envelope of Buildings and Their Causes
The following presents a basic methodology for the systematization of the analysis of the risks of climate factors and anomalies in masonry walls of the vertical envelope of buildings and their causes. Aiming to provide essential and systematized information about anomalies of the building envelope and their causes, especially those anomalies related to moisture presence and surface recession/cracking in masonry walls, it is intended here to define the principles of the basic methodology of analysis of anomalies in masonry walls and of their main causes, describing the main types of masonry and environmental actions on the building envelope, focusing especially on anomalies related with moisture presence and surface recession/cracking and developing it given their possible use in the survey and monitoring of these buildings with these types of anomalies (Figure 4).
Systematization Model for the Assessment of the Decrease of Performance of Buildings due to Anomalies of Their Envelope Related to Moisture Presence and Surface Recession/Cracking in Infill Masonry Walls.
The main characteristics of moisture presence and surface recession or cracking in buildings are generally discussed, and an evaluation is made of the main causes of cracking and moisture and their degradation effects in these types of masonry walls.
The data about construction anomalies gathered in the local survey inspection could be used for the characterization of the constituent elements of the vertical envelope and their anomalies, which allows the identification of the problematic issues, based on the following classification of anomalies: structural anomalies, functional anomalies, construction anomalies and anomalies in technical installations, framed by the situations of possible non-compliance with the construction basic requirements of construction.
Regarding the development of the classification system, the main focus of the analysis is on the effects of moisture presence and surface recession or cracking in masonry walls. To assess the relevance of these anomalies and their evolution along the service life, a corresponding survey needs the preparation of a framework of that classification system, which includes particularly the anomalies related to cracking and moisture presence in masonry walls of buildings, particularly due to water penetration associated with WDR.
Figure 5 presents an example of the basic structure of the framework of the systematization model for the assessment of the decrease in the performance of buildings due to anomalies of their envelope. The methodology, which aims at the systematization of the analysis of masonry walls through the generation of an identifying system of anomalies and their presumed causes (building model), involves the following main issues:
Information data on the characteristics of current types of external masonry walls in buildings; Information data on the characteristics of actions on the analysed building (temperature, humidity, wind, effects of climate change), their uses and alterations in original constructive conditions; Information data on the basic characteristics of the current types of anomalies in masonry walls of buildings; Survey of the building’s constructive characteristics (foundations, floors, walls and roof/anomalies and monitoring of anomalies in the masonry walls of the analysed building); Improvement planning—conservation and rehabilitation of the building (improvement of functional and constructive conditions).
Basic Structure of the Framework for Systematization of the Analysis of Masonry Walls.
Systematization of Climate Factors with an Impact on Buildings
With respect to the systematization of the impact of climatic factors (climatic parameters) on buildings, in particular, focused on hygrothermal actions, relevant risk factors (climate change risk) are selected for the systematization of the buildings and their recognized impacts (Sabbioni et al., 2009).
Regarding the impact of temperature change, the following risk factors are highlighted: diurnal, seasonal, extreme events (heat waves, snow loading); changes in freeze–thaw and increase in wet frost; deterioration of façades due to thermal stress; freeze–thaw/frost damage; damage inside masonry units (bricks and blocks becoming wet and frozen within material before drying); biochemical deterioration; sea-level rises; coastal flooding; sea water incursion; and coastal erosion/loss. The significant parameters for climate variables relevant in terms of temperature parameters could be essentially the following: temperature range, thermal shock and freeze–thaw cycles.
With respect to the impact of atmospheric moisture change, the following risk factors are highlighted: flooding (sea, river); intense rainfall; changes in water table levels and in soil chemistry; changes in humidity cycles; increase in the time of wetness; sea salt chlorides; physical changes to porous building materials and finishes due to rising damp; crystallization and dissolution of salts caused by wetting and drying, affecting standing structures; erosion of inorganic and organic materials due to flood waters; biological attack of organic materials by insects, moulds, fungi and invasive species such as termites; subsoil instability, ground heave and subsidence; relative humidity cycles/shock, causing splitting, cracking, flaking and dusting of materials and surfaces; and corrosion of metals.
The significant parameters for climate variables, useful in terms of atmospheric moisture, could be essentially the following: precipitation amount, total number of rainy days, extreme rain events, consecutive number of rainy days, mean relative humidity, relative humidity range and relative humidity shocks.
Concerning the impact of wind action, the following risk factors are highlighted: WDR; wind-transported salt; wind-driven sand; winds, gusts and changes in the direction; penetrative moisture into porous building materials; structural damage and collapse; deterioration of surfaces due to erosion and desertification; erosion; and salt weathering. The significant parameters for climate variables, useful in terms of wind action, could be essentially the following: wind-derived parameters, that is, wind speed, wind speed counts, WDR and wind-driven sand.
Relative to the impact of the combined action of climate and pollution, the following risk factors are highlighted: pH precipitation, changes in the deposition of pollutants, stone recession by the dissolution of carbonates, blackening of materials, corrosion of metals and influence of bio-colonialization. The significant parameters for climate variables that could be useful in terms of climate and pollution could be essentially the following: SO2, HNO3, O3 and pH precipitation.
With regard to the impact of climate and biological effects, the following risk factors are highlighted: the spread of existing and new species of insects (e.g., termites), increase in mould growth and the collapse of structural timber and timber finishes.
Systematization of Characteristics of Masonry Elements and of Anomalies/Causes in a Building’s Vertical Envelope
Regarding the systematization of the characteristics of masonry units, for example, in terms of the characteristic values of bricks (ceramic material), the following characteristics could be highlighted: apparent bulk density, water absorption by capillarity, open porosity, water absorption by cold immersion, linear thermal expansion and expansion due to humidity.
The systematization anomaly classification can be divided as follows: anomalies related to surface integrity and mechanical conditions (cracking (oriented cracking, mapped cracking and fracture/ splintering); crushing; detachment; disaggregation; spalling; erosion; loss of adhesion; wear of the wall render); anomalies related to the presence of moisture and chemical conditions (leakage damp, colour changes, surface moisture, spalling or peeling, dirt and accumulation of debris and cohesion loss/ disaggregation and chalking); and anomalies related to pollution and biological conditions.
In particular, concerning the anomalies due to humidity, the following can be highlighted: efflorescence/cryptofluorescence, swelling, stains, loss of colour, moulds and fungi, disintegration of the joints and vegetation growth.
The causes are considered in relation to imposed actions, which could determine negative consequences in terms of anomalies (action/cause/effect). With respect to the systematization of the causes of anomalies, the following relevant issues could be highlighted: foundation settlement, temperature changes or extreme temperatures, seismic actions, water absorption, pollution, freeze-and-thaw cycles and cryptofluorescence.
Figure 6 presents a schematic structure of the analysis of anomalies in masonry walls and their causes, which could highlight the following issues: inspection techniques/diagnosis of anomalies/intervention solutions, structural and foundations anomalies, functional anomalies, description of the anomalies/forms of manifestation of the anomalies, possible causes of the anomalies, predictable evolution over time of the anomalies and its consequences and general intervention solutions.
Schematic Structure of Analysis of Anomalies in Masonry Walls and Their Causes.
Discussion
Prevention Against the Increase of Cracking and Moisture Presence due to the Impact of Climatic Factors
The forecast increases in the risk of heavier rain and an upsurge in temperatures, due to climate change, will harshly present environmental conditions, in terms of infiltrations of rainwater through cracks in the walls. It is expected that hygrothermal effects will influence the durability of the envelope of buildings decisively, particularly considering the established scenarios corresponding to assessments of the projected future changes using representative concentration pathways (RCPs) (Dias, 2023a, 2023b). For the scenario of high greenhouse gas emission, about RCP 8.5, the increased impact of hygrothermal effects on the building envelope could be previewed, if confronted with the corresponding impact forecast for the scenario of low greenhouse gas emission, Scenario A, about RCP 4.5. The first scenario (RCP 8.5) could be found to be more severe, in terms of a foreseeable higher intensity of rain and greater upsurge in temperature variations, due to climate changes, compared to that forecast for RCP 4.5 scenario (Dias, 2023a, 2023b). Concrete structures can be affected by extreme environmental effects of climate change, which could accelerate their degradation, which is highly dependent on the type of exposure of the structural elements to the aggressive degradation agents, particularly linked to environmental actions, and on characteristics of the concrete used (Fédération Internationale du Béton, 2006). Furthermore, in this context of climate change, the combined effects of changes in temperature, precipitation, atmospheric humidity, wind intensity and the concentration of some atmospheric pollutants that are deposited on the surfaces of buildings could significantly damage the building materials (Sesana et al., 2021).
In terms of an increase of knowledge of the subject of preservation of buildings, especially heritage buildings, expected to be severely threatened by climate change effects, intense research has been done particularly to study the decay phenomena occurring on building materials (e.g., surface recession, salt weathering on inorganic building material, and weathering processes on mortars) with progress in monitoring with new methods and implementation of experimental and numerical simulation techniques to study decay mechanisms on building materials and components, mainly on sites in diverse geographic locations and different environmental contexts (Bertolin, 2019).
Lately, there has been an increased concern regarding the reduction in building energy demand, particularly in the provision of climate change effects and especially in heritage buildings, considering that the heat losses through opaque components generate the maximum effect on the overall energy balance, the insulation of masonry walls has been the main focus of retrofit actions, but their efficacy has to be checked (Litti et al., 2015), especially in heritage buildings, with regard to the materials’ compatibility or regarding the change along a large period of the service life of the existing masonry hygrothermal behaviour (through quantifying the hygrothermal masonry performance by their monitoring onsite).
Buildings could become more vulnerable to climate change effects as a result of changing conditions, which modify and speed up the decay processes. Therefore, buildings need to progress to an adaptation process to face climate change effects, particularly through the identification of the factors that support or restrain that adaptation, especially in the case of heritage buildings.
Important Issues Related to the Quality Management of Building Conservation and Renovation for Minimizing Their Economic Costs and Improving Sustainability
To face environmental risks, it is important to evaluate the interest of assessing the impact of quality management procedures on the efficiency and overall performance of building conservation and renovation projects, especially the evaluation of non-compliance with the recommended construction rules of their present state-of-the-art. The upgrading of standards of quality of building conservation and renovation could not only improve productivity but also contribute decisively to reducing the global construction costs along the service life of buildings. Deficiencies in construction operations, lack of technology in labour or equipment, and inadequate materials incorporated in the construction could contribute to decreasing the anomalies in the infill walls of the building envelope. Furthermore, it could be considered convenient that the process of sustainable building conservation and renovation projects could be committed to sustainability (Aarseth, 2017).
Conclusions
An approach to management and conservation related to heritage buildings with the use of IT was presented, particularly with the description of the basic factors influencing moisture presence and surface recession/cracking in the vertical envelope of buildings and their respective impacts on durability. Examples were presented of moisture presence and surface recession/cracking in the vertical envelope of buildings with natural stone (laterite) masonry walls and buildings with RC elements and infill masonry walls.
Subsequently, the presence of moisture in the vertical envelope of buildings and the consequent risk of water penetration, growth of organic materials and deposition of pollutants (salts) due to the impact of climate factors were analysed. Surface recession or cracking in masonry walls of the vertical envelope of buildings and the risk of their increase due to the impact of climate factors were evaluated. Also, methods for the systematization of the analysis of the main anomalies of the vertical envelope of buildings and their causes were discussed.
A general definition of the basic methodology for the systematization of the analysis of the risk of climate factors and anomalies in masonry walls of the vertical envelope of buildings and their causes were presented followed by the systematization of climate factors with impact on buildings as well as the systematization of characteristics of masonry elements and of anomalies/causes in the building vertical envelope, aiming at the development of studies on the sustainability of buildings. Also with this aim, the prevention of the increase of cracking and moisture presence due to the impact of climate factors was discussed. Finally, important issues related to the quality of construction and management of the impact of environmental risks due to climate change in URM infill walls for minimizing their economic costs were presented.
Regarding the goal related to the need for the buildings to progress to an adaptation process to face climate change effects, more research is recommended, particularly aiming at the identification of the factors that support or restrain that adaptation, especially in the case of heritage buildings and also further deep study regarding material characterization as well as the correspondent material decay characterization for assessing environmental impacts and climate change effects.
Footnotes
Declaration of Conflicting Interests
The author declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.
Funding
The author disclosed receipt of the following financial support for the research, authorship and/or publication of this article: The Planned Research Programme of the ‘National Laboratory of Civil Engineering’ (LNEC) has funded this study.