J.M.P.Q. Delgado

Exterior condensations on façades: numerical simulation of the undercooling phenomenon

This article intends to apply existing numerical models of exterior boundary conditions on the simulation of exterior condensation on façades (undercooling phenomenon) finished with external thermal insulation composite systems. The results of three hygrothermal models were compared, regarding the temperature on the exterior surface of a west façade. The climatic conditions from Porto city were used. We analysed in detail how the simulation of the undercooling phenomenon is influenced by the numerical treatment of the radiative balance on the exterior surface. The numerical results show that these programs are useful tools in assessing the exterior condensation on façades and the importance of radiative balance on the exterior surface temperature. However, some differences were observed in the calculated values due to different parameters included in the radiative balance of the models.

Infrared Thermography Application in Buildings Diagnosis: A Proposal for Test Procedures

The study of hygrothermal behaviour is essential to evaluate the performance of construction components and building envelopes. Most building pathologies are related with temperature action. The use of non-destructive techniques to evaluate a building behaviour may be very useful as there is no need to destroy the building components, which would interfere with the user’s life. Infrared thermography is a non-destructive testing technology that can be applied to determine the surface temperature of objects. This technology has been applied to buildings for a couple of decades, to evaluate the building performance. It has been used to detect insulation defects, air leakages, heat losses through windows, moisture and different “hidden details”. This work evaluates the applicability of thermography to study the behaviour of building materials and building envelopes. A short literature review about thermography principles is presented. It is also showed the effect on the results of some factors that affect infrared thermography measurements. Several applications of infrared thermography to building diagnosis are listed, based on the work published by the scientific community. And finally, three test procedures are described in detailed to detect detachments on wall renderings, to evaluate the thermal comfort of floor coatings and to analyse the wetting and drying processes.

Hygrothermal Behavior, Building Pathology and Durability

Reducing the Risk of Microbial Growth on Insulated Walls by Improving the Properties of the Surface Materials.- Biological Defacement of External Thermal Insulation Composite Systems (ETICS).- Effectiveness and Durability of Biocides in Building Coatings - Biological Aspects.- Hygrothermal Conditions and Mould Growth Potential in Cold Attics - Impact of Weather, Building System and Construction Design Characteristics.- Controlled Ventilation of Historic Buildings - Assessment of Impact on the Indoor Environment via Hygrothermal Building Simulation.- Degradation Control of Historical Walls with Rising Damp Problems.- Hygrothermal Performance and Damage Risk of Green Roofs.- Applicability of the Pull-Off Test: Teachings from a Large Sample of In-Situ Tests.- Moisture Robustness during Retrofitting of Timber Frame Walls with Vacuum Insulation Panels - Experimental and Theoretical Studies.- Wind Resistance Evaluation to Dynamic Response of Mechanically Anchored Waterproofing Membrane System.-

Application of different transient sorption methods to evaluate moisture diffusion coefficients of building materials on the hygroscopic range

Typically, moisture transport coefficients are determined either by stationary measurements, as standard cup set-up and modified cup method, or by dynamic measurements, as the means of the type t rule in the initial phase of adsorption processes, logarithmic procedure in the end stage of adsorption processes, the half-time method, the moment method, and the hybrid 1-term method. The aim of this work was to test the usability of the five dynamic calculation methods to define the moisture diffusivity in the hygroscopic range of different building materials. The results obtained were compared in order to evaluate the discrepancies between the different calculation techniques. Advantages in time saving using each experimental technique were compared with the feasibility of each process. Two commonly used building materials are considered in the study, gypsum board and gypsum plaster, for adsorptive measurement of the moisture diffusivity at three different temperatures in three different relative humidity ranges.

Hygrothermal Performance and Degradation of Gypsum Houses in Different Brazilian Climates

This work consisted of two main lines of research: one of a literature review and other of simulation. In the first part, a modular constructive system based on gypsum blocks is presented. This constructive system reduces the manpower considerably, the time of execution and the final costs of construction. However, the durability assessment should be analysed but first its implementation and performance along the country must analysed.In this work a preliminary experimental characterization of the thermal conductivity, vapour permeability and water absorption coefficient of two different samples of gypsum plasters from the northeast Brazil (plaster pole of Araripe, Pernambuco) was performed. The experimental and analytical procedures followed either international standards or well-established methodologies, supporting the analysis of gypsum walls hygrothermal behaviour. The measured properties were adopted as inputs to hygrothermal simulation software and the analysis of gypsum based exterior walls was conducted for different climate zones and exposure conditions. The study demonstrates the durability issues that may arise in each location, due to differences in hygrothermal action.The other simulation part included hygrothermal advanced modelling, using the EnergyPlus software. The numerical results carried out allow a discussion over the interior comfort and durability of this modular constructive system. In this paper, the computer simulation model and the results of a parametric analysis of the dwelling performance on the eight climatic regions defined in Brazilian regulations are presented. The model was validated using the in situ measurements of air temperature.

Durability Assessment of Adhesive Systems for Bonding Ceramic Tiles on Façades: The Research and the Practice

The aim of this work is to give a contribution for the assessment of the durability of adhesive systems for bonding ceramic tiles on facades, based on experimental works carried out at the Building Physics Laboratory, Faculty of Engineering, University of Porto, Portugal (LFC—FEUP), in the perspective of both the research and the possible practical applications. The durability assessment of any construction material is not an easy task. The researchers must choose between several different approaches, each of which has advantages and limitations. While, in a building in use, the materials or components are subjected to varying actions in an environment where the great majority of the degradation agents are not controllable by man, in a laboratory, one can choose to expose the materials to artificial and controlled conditions, using climatic chambers for accelerated ageing. The main difficulty of this type of test lies in the interpretation of the results, in what concerns their correspondence to real time. Researchers on durability have been discussing this problem for a long time: how to get a valuable correlation between the results of accelerated ageing tests and the one issued from natural exposure. This work is presented in two different stages. In a first stage, a discussion on durability assessment is presented based on an experimental research study, concerning the performance over time of different types of cementitious adhesives exposed to accelerated ageing tests and also to natural ageing. The main advances and the main difficulties in implementing a service life prediction model are identified. Suitable strategies are discussed for the future development of this approach. In a second stage, an extensive case study is presented. The main goal of this case study is to evaluate the durability of alternative adhesive systems for bonding ceramic tiles on the facades of a building, located near the sea. For this purpose, accelerated ageing tests are performed following two different ageing procedures, allowing the comparison of the performance over time of the systems under analysis.

Hygrothermal performance of Brazilian gypsum walls

The aim of this article is to evaluate the hygrothermal behaviour of gypsum walls in the climatic diversity of Brazil, based on the action and interaction between external climatic variables and the facade element. First, a laboratory characterization of material properties for the gypsum was carried out to determine their hygrothermal behaviour, particularly water vapour permeability, capillary absorption, retention curve and thermal conductivity. Second, the wall system performance was also evaluated in terms of its watertightness. It was concluded that the addition of a silicone water-repellent, typically used by the local industry, could lead to a classification of preventive against water. It was also concluded that a content of water-repellent above 0.5% would not result in additional benefits regarding watertightness. The second part of this work was focused on the evaluation of the hygrothermal behaviour of the standard and the water-resistant gypsum walls by means of hygrothermal numerical simulation. This analysis was intended to assess the influence of various factors such as the wall components (namely, wall coatings), the climatic conditions by geographical location and also the interior conditions, the orientation of the facades and the driving rain. The results demonstrated that the Brazilian climatic diversity can lead to very different exposure conditions. The locations in Interior Northeast Brazil, which are especially dry, corresponded to the ones with lower moisture content results. The results showed that gypsum masonry application on facades, with unfavourable climatic contexts, high precipitation and low solar exposure, would result in low durability. Only future works, including in situ studies may support the justification for applying the studied solutions in facades in favourable climatic conditions.

Case Studies of Rising Damp Treatment in Historical Buildings

Salt damage can affect the service life of numerous building structures, both historical and contemporary, in a significant way. Therefore, various conservation methods have been developed for the consolidation and protection of porous building materials exposed to the salt attack. As any successful treatment of salt damage requires a multidisciplinary attitude, many different factors such as salt solution transport and crystallization, presence and origin of salts in masonry, and salt-induced deterioration are to be taken into account. The importance of pre-treatment investigations is discussed as well; in a combination with the knowledge of salt and moisture transport mechanisms they can give useful indications regarding treatment options.Another important cause of building pathologies in buildings is the rising damp and this phenomenon it is particularly more severe with the presence of salts in water. The treatment of rising damp in historic building walls is a very complex procedure. At Laboratory of Building Physics (LFC-FEUP) a wall base hygro-regulated ventilation system was developed. This system patented, HUMIVENT, has been submitted to laboratorial monitoring and to in situ validation and a numerical simplified model was developed to facilitate the practical application. Having in mind the practical application of scientific and technological knowledge from Building Physics to practice, this paper presents the design of the system (geometry, ventilation rate and hygrothermal device), the detailing and technical specification of its different components and information about the implementation in three types of buildings: a church, a museum and a residential building.

Moisture Measuring Device Based on Non-Destructive Method of Gamma Ray’s Attenuation

A moisture measuring device based on non-destructive method of gamma rays attenuation, allows measures to deepen concepts in building physics related to the moisture transfer; study the influence of the interface between layers in moisture transfer; analyse the influence of gravity on absorption and drying of different building materials; study the kinetics of absorption and drying of walls of one or more layers; analyse the importance of the temperature gradient in the movement of moisture; calculate the coefficient of water diffusivity of some building materials. In this work the proposed non-destructive method of gamma ray’s attenuation was used to analyse the transport of liquid water along a constructive element. For that propose gamma ray hydric profiles with red brick samples, 2 types: “A” and “B”, were obtained. Gamma ray hydric profiles are very interesting and original considering that the equipment exists in just a scarce laboratory. It is also intended to show how the equipment works and the way that those profiles can be taken. The water content profiles experimentally measure are very interesting, and the preliminary results obtained, for red brick samples with different densities and sectional area, will be shown and discussed.

The Rising Damp in Cultural Heritage: From Physical and Numerical Analyse to Practical Application

The main goal of this work is to present a complete review of rising damp treatment in building heritage using a technique developed in our group to estimate and mitigate the height of the rising damp front and to predict the improvements of some experimental treatment techniques. The paper present a mathematical and a numerical analyse of the problem; an experimental and a practical application of the technique developed. This work is distributed into six main sections, in addition to this general Introduction: This book chapter is divided in several sections. Initially, it is presented the “state of the art” synthesis, where it is studied the techniques traditionally used for the rising damp treatment, showing the existing limitations on its application in monumental heritage and in old or ancient buildings, with specific characteristics. Then, it is performed the idea and the operating principle of the new technique, known as the wall base ventilation system, on the basis of previously conducted studies. An analytical, numerical and “in-field” study it is presented based in a case study described in detail. Finally, it is done a critical analysis of the results obtained, projecting the future work.