Papers by Author: A.S. Guimarães

Abstract: Climate change is one of the most debated issues today around the world, given its global impact. The construction industry in the European Union (EU) accounts for 40% of energy consumption and 36% of greenhouse gas emissions. Thus, the continuous improvement of energy efficiency in buildings plays a key role in achieving the carbon neutrality goal by 2050. At a time when the irreversible point of global warming may have already been reached, change becomes urgent, with one of the solutions being the use of renewable energies. Among renewable energies, solar is considered not only one of the most promising ones but also one of the energies with the greatest potential growth. The accelerated use of solar PV allows a reduction of carbon dioxide of approximately 4.9 gigatonnes. In the last decades, solar panels presented a great improvement in their efficiency and power output over and, in addition to the production of electricity, their heat can also be harnessed. Therefore, the objective of this work is to study a photovoltaic panel solution in which the heat produced indirectly by it contribution to the heating of a house and, consequently, to thermal comfort. In this work, it was analysed the feasibility of a PV solution that intends to take advantage of the hot air, indirectly produced by it, for subsequent heating of a house. Numerical simulations were performed using Ansys^® Fluent, Release 18.1, software and considering a 3D model of a house with PV panels installed in the roof. The results showed the solution under study is not feasible in winter, since solar radiation is not enough for heating using this contribution. However, this solution, although not avoiding the use of other heating means, can help in heating, contributing to the reduction of some needs.

Abstract: In addition, the majority of electricity consumed in buildings (58%) should come from renewable sources. Together with solar thermal, modern biomass, and district heating, overall renewables could ramp up to 81%, from 36% today’s contribution for the sector. Nonetheless, to materialize these predictions, a global investment of around USD 32 trillion (28 trillion euros) is expected between now and 2050. In the European Union, the nearly zero-energy building standard (nZEB) will be obligatory for all new buildings by 2021. Although the increase in energy demand will be reduced with this measure, it does not really affect the energy consumption at present. It is imperative to design energy efficiency retrofit and renovation financing schemes. For many years to come, only measures taken in existing buildings will have a significant effect on the total energy demand in the building stock. Firstly, this work presents a brief analysis of active and passive solutions for an energy-efficient building. Secondly, in this work it identified a set of active and passive solutions, which, in a combined way, develop the thermal performance of a residential building, allowing it to become energetically autonomous. The program EnergyPlus was used to execute the thermo-energetic simulations for the diverse scenarios considered, in the study case. The numerical results showed that the implementation of passive solutions improves the energy performance of the buildings, and the use simultaneously of an active solution, a renewable energy source, allows the reach of the energy-autonomous of the building.

Abstract: The main goal of this work is the analysis of the thermal and environmental benefits of 3D printing on building construction. Present literature reports a considerable number of benefits for 3D printing, namely reduction of material use, lower operational costs and time saving. Authors also mention design freedom, higher efficiency, productivity and quality. This work presents the most important advances in 3D printing in civil engineering, specifically, a critical review of the thermal and environmental benefits of 3D printing on building construction. The limitations of construction 3D printing with focus on large-scale applications, technology costs, mix development and optimisation and thermal behaviour will be, also, defined.

Abstract: The future of construction will be directly connected with additive manufacturing (AM). It is easy to see the lack of consistency between jobs, labour inefficiency, schedule delays, delays on material delivery, exceeding budget projections and high percentage of material waste. Over the years, additive manufacturing has been a constant topic of discussion, in order to understand the limitations, applications and the overall impact on the cost of construction. In this work it is intended to present/discuss opportunities and challenges and the potential of AM to revolutionize the industry.

Abstract: The knowledge of moisture transfer in multi-layered building materials and components using numerical simulations is fundamental to predict the behaviour of that building materials and components when in contact with moisture and to avoid some possible future pathology guarantying a correct performance.This paper describes a comparative analysis of experimental values of Hygric Permeance (HP) obtained by water absorption curves and gamma-ray attenuation profiles, for perfect contact interface. ARTICLE REVISED ON 25.03.2022

Abstract: After intensifying the knowledge of hygric permeance (HP) in multi-layered test samples, which were subjected to the imbibition process, a significant set of HP values (with different interface types) was experimentally achieved. This was done in order to develop a new model which allows estimating more correctly the hygric permeance. The idea is predicts the HP with several scenarios, i.e., different interfaces (perfect contact, hydraulic contact and air space interface), interfaces heights and materials studied, in the attempt to estimate the HP without the need to resort to the measurement by the experimental route in the attempt to estimate the HP without the need to resort to the measurement by the experimental route and even with possible measurement, generator automatic calculation (without human opinion/criteria). In this paper, the Hygric Permeance will be calculated by two different methods, gravimetric and gamma ray methods, and a new methodology proposes. The maximum flows transmitted were determined by the slope of the mass variation per contact area in function of the time involved. When having interface, the calculations admit that the first layer is saturated and that all the increased weight stems becomes from the relative humidity that penetrates the interface. The new methodology proposed is analysis of the prevision mathematical model that describes the mass variation per contact area in function of the time, after the “knee point”. This work it is the first attempt to provide a set of values that refer from hygric permeance in masonry of building walls, these being random values experimentally determined.

Abstract: The phenomena of transport in porous media arises in many diverse fields of science and engineering, ranging from agricultural, biomedical, building, ceramic, chemical, and petroleum engineering to food and soil science. Several authors provide an extensive description of the problems involving porous media. For building engineering, obtaining a good understanding of moisture transport in building envelopes is becoming one of the most important tasks. In the last few decades, many studies investigating moisture transport in building envelopes have been published, which have helped to improve overall building envelope design. This work presents a brief review of these studies.

Abstract: 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.

Abstract: 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.

Abstract: Rising damp is one of construction’s major problems associated with use of porous materials in this industry. This mechanism has a massive influence on the degradation of historical buildings since they were built in a time when construction technologies made no effort to prevent this kind of pathologies. The rising damp by itself can reduce the aesthetical value of the building and, when combined with the existence of soluble salts in the building and in the ground water can even lead to material decomposition and compromise the structural performance of the building. This happens due to the migration of the salt ions dissolved in water into the porous network of the building’s walls where they remain and crystalize after water evaporates, dealing great pressures against the pore walls and eventually resulting in their fracture after many cycles of crystallization/dissolution.The experimental work intended to study the effect of two different saturated solutions of sodium sulphate and potassium chloride in the capillary absorption curves obtained through the partial immersion of red brick samples. In the end of this paper there will be a macroscopic evaluation of the sample’s crystallized top surface, obtained after a partial drying period. The results revealed significant differences in the capillary coefficients obtained when samples were tested with salt solutions.