Vasco Peixoto de Freitas

Discussion of Criteria for Prioritization of Predictive Maintenance of Building Façades: Survey of 30 Experts

The practice of predictive maintenance depends significantly on the diagnosis of in-service performance and on the decision criteria for the selection of maintenance tasks. The definition of these criteria is limited because several actors are involved, each with their own perspectives of performance and maintenance needs. This paper discusses a set of 17 criteria to help the maintenance choice for building facades, from three viewpoints: physical performance, risk, and costs. A group of experts was surveyed and 30 answers were received. Therefore, each criterion will be discussed according to the answers collected. The relative importance (using quantitative weights) and subclasses for each criterion are proposed.

On‐site performance assessment of rendering façades for predictive maintenance

Purpose – The purpose of this paper is to present a methodology in order to improve inspections diagnosis during facades service life through in‐service criteria. On‐site performance assessment and deciding on the maintenance of renders can only be improved if quantitative parameters are pre‐established at the design stage and monitored under service conditions.Design/methodology/approach – The methodology is based on a set of in‐service parameters inferred from visual observation and measurements and their methods of assessment (based on visual inspections, auxiliary techniques, in‐situ and laboratorial testing). These have been arrived at by inspecting the facade rendering on 44 buildings (cement‐based renders), of different ages and types of degradation.Findings – This paper focuses on 23 proposed mechanical and physical‐chemical parameters that can complement the ones already established by standards or technical data, obtained in lab conditions, using standard specimens or small models. They are as...

Rising Damp in Walls: Evaluation of the Level Achieved by the Damp Front

Treating rising damp in the walls of historical buildings is complex because moisture transfer into the walls of old buildings in direct contact with the ground leads to the migration of soluble salts. This work analyzes rising damp using concepts and methods of unsaturated moisture flow theory, and a numerical validation study. A simple analytical model describes the rising damp front for the simplified situation of a monolithic wall. The influence of wall thickness, boundary conditions, wall composition, and material properties, such as porosity and sorptivity, are analyzed in detail.

External Thermal Insulation Composite Systems: Critical Parameters for Surface Hygrothermal Behaviour

External Thermal Insulation Composite Systems (ETICS) are often used in Europe. Despite its thermal advantages, low cost, and ease of application, this system has serious problems of biological growth causing the cladding defacement. Recent studies pointed that biological growth is due to high values of surface moisture content, which mostly results from the combined effect of exterior surface condensation, wind-driven rain, and drying process. Based on numerical simulation, this paper points the most critical parameters involved in hygrothermal behaviour of ETICS, considering the influence of thermal and hygric properties of the external rendering, the effect of the characteristics of the facade, and the consequences of the exterior and interior climate on exterior surface condensation, wind-driven rain, and drying process. The model used was previously validated by comparison with the results of an “in situ” campaign. The results of the sensitivity analyses show that relative humidity and temperature of the exterior air, atmospheric radiation, and emissivity of the exterior rendering are the parameters that most influence exterior surface condensation. Wind-driven rain depends mostly on horizontal rain, building’s height, wind velocity, and orientation. The drying capacity is influenced by short-wave absorbance, incident solar radiation, and orientation.

Hygrothermal numerical simulation: application in moisture damage prevention

1.1 Background Building pathologies originated by moisture are frequently responsible for the degradation of building components and can affect users’ health and comfort. The solutions for treating moisture related pathologies are complex and, many times, of difficult implementation. Several of these pathologies are due to innovative techniques combined with new materials of poorly predicted performance. The knowledge of the physical processes that define hygrothermal behaviour allows for the prediction of a building response to climatic solicitation and for the selection of envelope solutions that will lead to required feasibility. Over the last five decades, hundreds of building energy software tools have been developed or enhanced to be used. A list of such tools can be obtained in the US Department of Energy Webpage (2007). This directory provides information for more than 345 building software tools for evaluating energy efficiency, renewable energy and sustainability in buildings. The problem of moisture damage in buildings has attracted interest from the early days of the last century, but it was during the past decades that the general topic of moisture transport in buildings became the subject of more systematic study, namely with the development of the modelling hygrothermal performance. In the field of building physics the hygrothermal models are widely used to simulate the coupled transport processes of heat and moisture for one or multidimensional cases. The models may take into account a single component of the building envelope in detail or a multizonal building. In literature, there are many computer-based tools for the prediction of the hygrothermal performance of buildings. These models vary significantly concerning their mathematical sophistication and, as shown Straube and Burnett (1991), this sophistication depends on the degree to which the model takes into consideration the following parameters: moisture transfer dimension; type of flow (steady-state, quasi-static or dynamic); quality and availability of information and stochastic nature of various data (material properties, weather, construction quality, etc.). All the hygrothermal simulation tools presented later in this paper are based on one of the following numerical methods for space and time discretization: a. Finite Difference Methods (FDM) and Finite Control Volume (FCV) methods; b. Finite Element Method (FEM); c. Response Factor and Transfer Function method.

Energy and Water Consumption Variability in School Buildings: Review and Application of Clustering Techniques

AbstractIn developed countries, the building sector is responsible for a very significant share of the total energy consumption. School buildings, because they are places where children are educated and learn to become active members of the society, should be a good example of an efficient use of energy and water. In this study, data of the energy and water consumption of 23 Portuguese schools and their main building characteristics and properties were gathered. This information was normalized to homogenize the data set and then analyzed using advanced clustering techniques. The results show a significant variability in the consumption of different schools, even with similar characteristics, suggesting that the user behavior plays an important role in their efficiency. The complete linkage and Ward’s clustering methods were applied, both produced three clusters, and reference values for electricity and water consumption were defined.

Evaluation of Surface Humidification of Exterior Insulation and Finish Systems

AbstractExterior insulation and finish systems (EIFSs) are common in Europe nowadays. These systems bring thermal benefits, in addition to being cheap and easy to apply, but there are often serious problems with biological growth, causing cladding defacement. The physical phenomenon causing EIFS defacement is known, and mathematical models simulating its performance have been developed. However, no simple process exists to evaluate the risk of EIFS surface humidification (which contributes to surface defacement) that might be used by designers and by the building industry. This paper presents a methodology to assess EIFS surface humidification based on the definition of indices that combine the effect of surface condensation, wind-driven rain, and the drying process, three of the most prevalent parameters influencing surface moisture content. The proposed indices were calculated using data collected during a 1-year in situ test campaign, which provided information about the exterior climate conditions and...