Laboratory tests of window-wall interface details to evaluate the risk of condensation on windows

The development of alternative details to manage water intrusion at the window-wall interface has produced a number of novel approaches to detailing the interface between the window and adjacent wall assembly. Many of these approaches advocate the need to provide drainage at the rough opening of the window subsill given that the window components themselves are susceptible to water entry over their expected life. Depending on the types of windows used and the cladding into which the windows are installed, there arise different methods to provide drainage that may also affect air leakage through the assembly. This in turn may give rise to the formation of condensation along the window at the sill or along the window sash and glazing panels. Hence there is a need to determine if, under cold weather conditions, specific interface details that incorporate sill pans provide potential for condensation on the window components in which air leakage paths may be prominent at the sill or elsewhere on the window assembly. The paper reports on a laboratory evaluation of conditions suitable for the formation of condensation at the window frame perimeter of the interface assembly as a function of both temperature deferential and air leakage rate across the test assembly. A summary of the laboratory test protocol is provided that includes a description of the test set-up and apparatus, fabrication details of the specimen and information on instrumentation and calibration and experimental results for one type of window (flange window). In parallel, preliminary simulation results were presented and compared to those obtained from experiment using the commercially available thermal software BISCO

Analysis of the Measurements Reliability in Dynamic Test of the Opaque Envelope

The characterization of the thermal behaviour of opaque building components is essential in early design stage to compare different alternatives. The evaluation of the dynamic thermal response to the external solicitation is necessary for an effective design study especially for the climates with important annual cooling demand, such as Southern European ones. According to EN ISO 13786, opaque elements can be characterized through some dynamic parameters (i.e., periodic thermal transmittance, time-shift, decrement factor), which can be calculated starting from the wall materials’ thermal properties. However, when either the material thermo-physical properties are unknown (e.g. in existing buildings) or the assumptions on which the method is based are not met (e.g. in platform-frame structures), the calculation method does not assure enough accuracy of results. Hence, for these components, a direct measure of these parameters would be extremely useful. Differently from the procedure to determine the steady-state thermal transmission properties, which is well established, there are no standard rules for the experimental measurement of the dynamic parameters. Nevertheless, as demonstrated by some recent works in the literature, it is possible to estimate EN ISO 13786 dynamic parameters from non-destructive measurements based on heat flow meters, HFM. Since these experimental procedures are still under development, the extent to which several aspects limit the accuracy and precision of the measurements are not yet cleared. In this framework, this work presents a theoretical and experimental analysis about the achievable reliability of the post-processing procedure for the evaluation of the dynamic characteristics of opaque constructions by means of HFM-based measurements in modified hotbox apparatus. Experimental and numerical tests have been performed in order to assess the impact of different sources of uncertainty on the estimation of EN ISO 13786 dynamic parameters. In this regard the main source of errors investigated deal with the sample and the hotbox apparatus, e.g. the boundary effects in heat conduction, the edge guarding of the HFM, the noise of eddy close to HFM surface, the stability in time and space of the surface temperature of the sample and the HFM assembly modality. Moreover, several aspects of the HFM are also investigated, such as the HFM calibration curve, the effect of HFM emissivity and the response time constant. A multi-layer timber wall construction has been tested in a modified hotbox apparatus with different boundary conditions, regarding, in particular, temperatures and convective heat transfer mechanisms imposed at the two sides of the specimen. A numerical model of specimen and apparatus has been also developed and calibrated against the experimental data. With this model, we have investigated further conditions related to the material properties and dynamic forcing solicitation, including the noise affecting the thermal field because of the HFM itself. The relative impacts of the different error sources have been quantified, in order to assess future applicability of HFM dynamic approach for in-situ measurements

The potential of the reed as a regenerative building material—characterisation of its durability, physical, and thermal performances

Knowing the properties of vernacular materials is crucial to heritage conservation and to develop innovative solutions. Reed, considered to be a carbon-neutral and a carbon dioxide sink material, has been used for centuries for diverse uses. Its high availability and properties made it a popular building material, including in Portuguese vernacular architecture. An experimental investigation was conducted to evaluate the physical performance, thermal performance, and durability of the reed found in Portugal since the characterisation of this material was not found in previous studies. The influence of geometric characteristics and the presence of nodes on these properties were also analysed, and the results showed that they are irrelevant. The studied reeds were found to have an adequate thermal performance to be used as thermal insulation. Their thermal resistance (1.8 m2·°C/W) and thermal conductivity (0.06 W/m·°C) are under the requirements defined by Portuguese regulations on thermal insulation materials. Overall, the physical characteristics (moisture content, density, and retraction) are compatible to its use in the construction. Concerning durability, there was only a trend for mould growth in particular environments. The results provide valuable data to be considered in the development of new construction products based on this natural and renewable material. Additionally, considering the studied samples, the reed found in Portugal has characteristics suitable for use as a building material, especially as a thermal insulation material.FEDER funds through the Competitively and Internationalization Operational Programme (POCI) and by national funds through FCT (the Foundation for Science and Technology) within the scope of the project with the reference POCI-01-0145-FEDER-029328, reVer

Development of affordable hot box calorimeter to determine the U-value of inhomogeneous building material

open access articleIn recent years, the use of three-dimensional printing to create construction components has advanced quickly; it is possible now to simplify construction, increase speed, and lower cost while using natural resources responsibly. It also allows us to use recycled material to produce building envelopes while increasing design flexibility. However, the thermal performance of building materials must be characterized to achieve the necessary energy efficiency of the building envelopes. This study aims to develop, produce, and calibrate a hot box calorimeter at a reasonable price for thermal testing components building envelope. The heat loss through these components using a hot box can be measured in a lab to get an idea of the thermal performance of the building envelopes. In order to evaluate and analyze the thermal performance of various 3D-printed building brick samples made in the labs, this study explains the design and creation of an inexpensive hot box. The hot box can conduct a conventional thermal experiment, which involves monitoring heat flux, surface temperatures, and air temperatures. The testing process, instrumentation, test conditions, and validation of the new metering box are all covered in the article. The U-value of the brand-new lattice-based 3D printed building blocks was afterward determined using the validated new hot box. It was observed that the U-values values of 1.04 W/m2.K and 0.99 W/m2.K, respectively, for small components utilizing developed hot box and larger lattice panels using commercial equipment, with a maximum variance of 5%. It highlights the dependability of the hot box apparatus, which is also made affordable to operate by using less material for specimen preparation and less energy to maintain the temperature in the hot and cold chambers. Its small size also makes setup and thermal testing of construction materials simple

Mechanical and thermal performance characterisation of compressed earth blocks

The present research is focused on an experimental investigation to evaluate the mechanical, durability, and thermal performance of compressed earth blocks (CEBs) produced in Portugal. CEBs were analysed in terms of electrical resistivity, ultrasonic pulse velocity, compressive strength, total water absorption, water absorption by capillarity, accelerated erosion test, and thermal transmittance evaluated in a guarded hotbox setup apparatus. Overall, the results showed that compressed earth blocks presented good mechanical and durability properties. Still, they had some issues in terms of porosity due to the particle size distribution of soil used for their production. The compressive strength value obtained was 9 MPa, which is considerably higher than the minimum requirements for compressed earth blocks. Moreover, they presented a heat transfer coefficient of 2.66 W/(m2·K). This heat transfer coefficient means that this type of masonry unit cannot be used in the building envelope without an additional thermal insulation layer but shows that they are suitable to be used in partition walls. Although CEBs have promising characteristics when compared to conventional bricks, results also showed that their proprieties could even be improved if optimisation of the soil mixture is implemented.The authors would like to acknowledge the support granted by the FEDER funds through the Competitively and Internationalization Operational Programme (POCI) and by national funds through FCT (the Foundation for Science and Technology) within the scope of the project with the reference POCI-01-0145-FEDER-029328, and of the Ph.D. grant with the reference PD/BD/113641/2015, which were fundamental for the development of this study

Reed as a thermal insulation material: Experimental characterisation of the physical and thermal properties

The building sector plays a significant role in reducing global energy use and carbon emissions. In the European Union (EU), the building stock represents 40% of total energy use and in which cooling and heating systems represent over 50%. Portugal is one of the EU countries where the consequences of energy poverty are most evident due to the families' financial inability to adequately climate their homes. The reasons are several, but they are mainly linked to buildings' poor passive thermal performance, resulting from inadequate adaptation to the climatic context and reduced thermal insulation. Thus, it is necessary to develop solutions to increase buildings’ thermal performance and reduce their potential environmental impact, which arises mainly from the significant use of active systems. In this sense, natural building materials are a promising solution, reducing energy use and carbon emissions related to buildings. This research studies the potential use of reed found in Portugal (Arundo donax) as a thermal insulation material. Its physical characterisation and the influence of geometry configuration on its thermal performance are evaluated. Its durability was studied too. Reed stalks were used to carry out the physical and durability tests. A reed board (150 x 150 mm) was built, and its thermal performance was tested in a hotbox. According to the results, the characteristics of reeds found in Portugal make it suitable to be used as a building material. Furthermore, regardless of the configuration studied, the reeds have a satisfactory thermal performance to be used as thermal insulation, under the requirements defined by Portuguese thermal regulation, Re ≥ 0.30 (m2.oC)/W. There is a trend to the mould growth in the reed, but only under favourable conditions. Additionally, considering the abundance of reed throughout the Portuguese territory, this is an eco-friendly and low-cost option that gathers all requirements to be more used in the construction market

Aplicação do método de estado estacionário (hotbox) para a caracterização das propriedades térmicas de diferentes produtos de construção

A atual crise ambiental e energética impulsiona a busca por construções mais eficientes e de menor impacte ambiental. Este estudo investiga a aplicação da hotbox, conforme normas ISO 8990 e ISO 9869, para avaliar o desempenho térmico de materiais de isolamento. Desafios experimentais, como controlo de temperatura e movimentação do ar e perdas de calor são abordados para garantir a obtenção de parâmetros térmicos confiáveis. O estudo analisa produtos diversos, nomeadamente placa de poliestireno extrudido (XPS), painel de canas Arundo Donax e blocos de terra comprimida (BTCs), destacando a adaptabilidade da hotbox. A metodologia abrange a revisão de literatura, focada na análise dos princípios de medição em hotbox e a caracterização das propriedades térmicas de materiais inovadores. Resultados indicam a capacidade deste equipamento em caracterizar propriedades térmicas de materiais distintos e origens diversas. Conclui-se que a aplicação da hotbox é vantajosa desde as fases mais preliminares do desenvolvimento de novos produtos, para que estes atendam às exigências e regulamentações térmicas atuais. Além disso, são apresentadas as propriedades térmicas de materiais alternativos de base biológica e mineral, promovendo a sustentabilidade no ambiente construído. O estudo ressalta ainda a importância da medição precisa para a construção sustentável e energicamente eficiente.Este trabalho foi parcialmente financiado pela FCT/MCTES através de fundos nacionais (PIDDAC) no âmbito da Unidade de I&D Instituto para a Sustentabilidade e Inovação em Engenharia de Estruturas (ISISE), com a referência UIDB/04029/2020 (doi.org/10.54499/UIDB/04029/2020), e no âmbito do Laboratório Associado Produção Avançada e Sistemas Inteligentes (ARISE) com a referência LA/P/0112/2020. Este trabalho foi também financiado por fundos do Fundo Social Europeu (FSE) e do Programa POR NORTE através da FCT - Fundação para a Ciência e Tecnologia e do Programa MIT Portugal, ao abrigo do contrato de subvenção atribuído ao 1º autor (SFRH/BD/151345/2021) e ao 3º autor (PRT/BD/152839/2021)