Parede de trombe: análise experimental e simulação de desempenho térmico

A necessidade de redução do consumo de energia nos edifícios exige que se adoptem medidas de melhoria do desempenho energético de edifícios novos e existentes. Uma das formas de alcançar este objectivo consiste na integração de soluções construtivas mais sustentáveis, como por exemplo, os sistemas solares passivos. Apesar de o aproveitamento da energia solar através deste tipo de sistemas ser uma técnica bastante antiga, o recurso aos sistemas solares passivos não constitui, actualmente, uma prática muito corrente na construção, diminuindo a sua aplicação no que se refere aos sistemas passivos de ganho indirecto. A parede de Trombe é um sistema de ganho indirecto e a sua integração na envolvente dos edifícios em Portugal é escassa devido à falta de informação por parte dos diversos intervenientes do sector da construção, no que respeita ao seu desempenho energético e às suas características construtivas. No sentido de contribuir para o aumento do conhecimento científico nesta área, apresenta-se neste trabalho a análise experimental e a simulação do desempenho térmico da parede de Trombe sujeita a condições climáticas reais na cidade de Vila Real. A análise experimental englobou o projecto, construção, instrumentação e monitorização de um dispositivo experimental, constituído por uma célula de teste que incluiu a construção de uma parede de Trombe. Nesta fase foi possível analisar os valores obtidos relativos às temperaturas na parede acumuladora, na caixa-de-ar e nas aberturas de ventilação, para a parede de Trombe sujeita à influência dos dispositivos de sombreamento. Para além da análise experimental, foi também aplicada uma metodologia de cálculo do desempenho térmico da parede de Trombe com carácter dinâmico, implementada em ambiente de programação MatLab que permitiu calcular os ganhos totais através deste sistema. A análise efectuada permitiu definir os períodos de actuação do sistema de ventilação e do dispositivo de sombreamento exterior que melhor se adaptam às estações de aquecimento e de arrefecimento, bem como aos períodos diurno e nocturno. Concluiu-se assim, que o trabalho desenvolvido nesta tese constitui um contributo válido para o melhor conhecimento do desempenho térmico da parede de Trombe, o qual constituirá um incentivo para a sua maior aplicação em edifícios novos e existentes

Thermal and acoustic performance of interlocking compressed earth blocks masonry

The earth construction is an ancient building technique that, with the emergence of new materials and technologies, has received less attention during the last decades. Nevertheless, the new concerns in terms of environmental protection and sustainable construction have recently led to its revalorization. The masonry construction with interlocking compressed earth blocks (ICEB) is one of the earth construction techniques that features several advantages and has received the most developments in the last years. This type of masonry is currently being used worldwide, especially in developing countries, although the suspicions about its performance remain very wide. Another problem is the lack of standards and documents that can support designers in projects development. This research aims to contribute in this direction, creating bases to help designers in their work and contribute to the knowledge about this type of construction. Furthermore, there has been an increase in the standard requirements related to the comfort inside the building, namely at the thermal and acoustic level. So, the knowledge of the thermal and acoustic performance of the ICEB masonry is essential to define and optimize the constructive solutions at the design stage. Experimental studies were carried out in order to characterize these properties. The results are presented and discussed. It is expected that the results obtained serve as design support for this type of construction.FEDER funds through the Competitivity Factors Operational Programme - COMPETEFCT – Foundation for Science and Technology- project POCI-01-0145-FEDER-00763

Nature-based solutions contribution for urban resilience and sustainability

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Thermal performance characterization of cement-based lightweight blocks incorporating textile waste

Textile industry is one of the most important sectors of the global economy, but at the same rate as production, millions of tons of textile waste (TW) are generated worldwide, causing negative impacts on the environment. To mitigate CO2 emissions and TW landfilled, its reuse and recycling are considered promising in fulfilling the circular economy principles. Furthermore, its valorization as building materials components may be a contribution towards sustainable construction. Studies already developed in this domain demonstrate that more research work is needed so the suitability of TW as building insulation materials can be assessed. In this context, it is intended with the research work here presented to propose cement-based lightweight blocks (LWB) incorporating TW and discuss their application as insulation materials purposes. The studied TW was fabric leftovers from the textile industry, constituted by 70 % wool, 25% viscose, and 5% elastane. TW percentages of 6.25%, 8.16%, and 8.75% were considered in the cement mixture composition of LWB1, LWB2 and LWB3, respectively, and their influence on the LWB thermal performance was analyzed. The LWB thermal performance characterization was carried out by analyzing heat fluxes, inner surface temperatures, thermal transmission coefficients, and infrared thermal imaging. The obtained results revealed their suitability for thermal insulation applications. Values of 0.34 m2◦C/W, 0.61 m2◦C/W, and 0.67 m2◦C/W were estimated for the thermal resistance of LWB1, LWB2 and LWB3, respectively, achieving higher thermal stability when higher percentage of TW is incorporated in the cementitious mixture composition. A comparison of the LWB with currently available building materials, such as simple masonry walls and insulating concrete forms, was also performed showing promising results for the proposed textile waste-based materials.info:eu-repo/semantics/publishedVersio

Possible Applications of Corncob as a Raw Insulation Material

Some alternative applications of corncob as a raw thermal insulation material are presented in this research work. Usually, corncob has been treated as an agricultural waste. Finding practical applications of this waste in product manufacturing may preserve the environment and may also allow using more green technologies. Therefore, a corncob particleboard, a lightweight concrete for nonstructural purposes, and a lightweight concrete masonry unit (CMU) are the granulated corncob-based products proposed. These products are studied in terms of thermal performance, and some thermal parameters are delivered. The results obtained through the experimental study allowed to estimate the thermal conductivity of the granulated corncob and of the granulated corncob particleboards. The values obtained were 0.058 and 0.101 W/m°C, respectively. A thermal transmission coefficient of 1.99 W/m2°C was obtained for the nonstructural corncob lightweight concrete, and it was concluded that the density and the thermal properties of this alternative solution are in accordance with the properties of the currently used expanded clay concrete. For the granulated corncob lightweight CMU, a value of 1.15 W/m2°C was estimated. This shows that this agricultural waste may have potential as a thermal insulation product

Evaluating the fire behaviour of cement-based lightweight materials with textile waste incorporation using a cone calorimeter

The conscientious utilization of natural resources and the efficient waste management have become a matter of great concern in recent years due to the harmful impacts on the environment. The construction sector presents itself as one of the sectors that most contributes to raw materials consumption and waste generation, demanding the investigation of more sustainable and ecofriendly building materials, where the valorisation of wastes originated from other industries can be promising. Following the sustainability concept in construction materials, this work investigates the potential use of textile waste in cement-based lightweight construction material, evaluating the fire reaction of the material using the cone calorimeter equipment. The samples were tested at three different radiant heat fluxes (35 kW/m2, 50 kW/m2, 75 kW/m2) to simulate different fire situations. For the highest heat flux, the lightweight construction element with textile waste incorporation showed a Heat Release Rate Average ≤ 18 kW/m2, a peak Heat Release Rate Average ≤ 60 kW/m2, and a Total Heat Release Average ≤ 33 MJ/m2. These results reveal a very satisfactory fire behaviour compared to other materials and show the suitability of using textile waste as lightweight cement-based materials.info:eu-repo/semantics/publishedVersio

Editorial: urban nature-based solutions and green infrastructure as strategies for climate change adaptation

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A contribution for the improvement in thermal insulation of tabique walls coated with metal corrugated sheets

Tabique is a traditional Portuguese building technique using timber and earth and was intensively applied until the 20th century. There is an impressive tabique heritage that requires maintenance and rehabilitation interventions. Taking into account the facts that technical and scientific publications related to this particular technique are lacking and that the technique is also applied worldwide, this research work is a very relevant one. This study aims at studying the thermal insulation behaviour of tabique walls and in particular, tabique walls coated using metal corrugated sheets and thermally reinforced with an insulation material. This type of building component is initially characterized and some building details concerning the metal corrugated sheet coating are described. An experimental work was conducted to determine the thermal transmission coefficient of the tabique wall samples. It was concluded that providing the tabique wall coated with metal corrugated sheets with a 3 cm extruded polystyrene board results in a thermal insulation improvement of 61%. These results revealed that the thermal insulation reinforcement of tabique walls is possible and it may be a straightforward building procedure because it can be achieved using the thermal insulation building materials that are currently being used. Therefore, the thermal insulation reinforcement of tabique walls seems feasible. Furthermore, the thermal insulation parameters obtained in this study are similar to the ones obtained for currently applied walls solutions in new buildings. This technical fact may provide guidance for the possibility of using solutions used in old buildings to meet the thermal comfort requirements expected in today’s times. The knowledge gained will also be useful to support future proposals of energy rehabilitation solutions.info:eu-repo/semantics/publishedVersio

Mechanical characterization of masonry built with iCEBs of granite residual soils with cement-lime stabilization

The environmental impact due to the overexploitation of nonrenewable resources, the processing and transportation of materials, and waste production is a global concern that the construction industry must urgently address, since it is among the greatest contributors. Earth construction can be seen as an alternative building solution, enhancing sustainability, despite traditional techniques being nowadays in disuse in most developed countries. Construction with interlocking compressed earth blocks (iCEBs) is a recently developed technique, put in evidence in the last few decades, for overcoming many earth construction limitations. Here, this technique is studied as a sustainable building solution for Northern Portugal, where the typical soils are sandy, granitic residual soils with low clay content. These soils typically demand cement stabilization to produce earthen materials, which compromise the sustainability of the construction solution. In order to improve sustainability, stabilization with hydraulic lime is proposed as a partial replacement of cement. For this purpose, the properties of the selected soil were characterized through a set of geotechnical tests, with different percentages of cement and lime in the mixture composition tested, concerning the compressive strength of the specimens. A mixture composed of 87.5% of soil, 7.5% of cement, and 5% of lime was shown to be the most suitable for producing iCEBs with adequate mechanical performance. The compressive behavior of the iCEBs masonry was characterized by testing prisms and wallettes, considering both dry stack and mortar joints cases. The obtained results showed that using mortar in the bed joints allows for the improvement of the compressive strength (a 5%–18% increase) and Young’s modulus (a 65%–92% increase) of the masonry. Thus, it can be concluded that masonry built with locally produced iCEBs and stabilized with cement and lime is a feasible building solution, for a sustainable earth masonry built from sandy granitic residual soils, where the mechanical behavior is substantially enhanced by using bed-joint mortar.This work was partly financed by national funds, through the FCT Portuguese Foundation for Science and Technology, under the projects UIDB/00616/2020 and UIDP/00616/2020 for the Unit Institute CQ-VR and UIDB/04029/2020 for the Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE)

Edifícios de xisto no concelho de Peso da Régua

A pedra de xisto é um material natural e local comummente utilizado nas construções tradicionais do Concelho de Peso da Régua. Esta zona do Nordeste Português está inserida na região do Douro que é classificada como Património Mundial pela UNESCO. Os muros de divisão de terrenos, de suporte de terras e os edifícios de construção tradicional são os tipos de construção em que a pedra de xisto é o material dominante. Estas construções são parte integrante da paisagem e do património vernacular local, e por isso devem ser valorizados e preservados. Através deste trabalho de investigação foi possível realizar um levantamento dos edifícios de xisto existentes neste concelho, e reunir um conjunto de informações técnicas e construtivas que os caracterizam. Este artigo pretende divulgar informação técnica relativa a detalhes construtivos deste tipo de construção tradicional, focada principalmente nas suas especificidades estruturais. No contexto estrutural, as paredes de alvenaria de pedra de xisto são os elementos estruturais verticais principais. As dimensões e constituição das paredes, dos vãos de janela e de porta, dos cunhais e das padieiras são alguns dos aspectos técnicos e construtivos que merecem especial destaque, tendo em conta que podem influenciar de forma decisiva o comportamento estrutural deste elemento construtivo. Deste modo, pretende-se contribuir para o conhecimento deste tipo de construção, e disponibilizar informação base que possa suportar estudos futuros de modelação numérica e/ou ensaios experimentais do comportamento de paredes em alvenaria de pedra de xisto