SbCl5—wet acetonitrile: a new system for chemoselective O-desilylation

Abstract—A new efficient method for deprotection of TBDMS derivatives of phenols, primary alcohols, carboxylic acids and secondary amines, consisting of SbCl5 and MeCN with 0.1% water (w/v), is reported. It effects inter alia desilylation of a CH2OTBDMS group in the presence of a ketal function

Simulation-Based Evaluation of the Impact of an Electrochromic Glazing on the Energy Use and Indoor Comfort of an Office Room

Funding Information: The first author wishes to acknowledge the support of Fundação para a Ciência e a Tecnologia (FCT) for funding her PhD Grant FCT PD/BD/150576/2020 (DOI: 10.5449/PD/BD/150576/2020). The authors thank FCT for funding the Civil Engineering Research and Innovation for Sustainability (CERIS) research unit through UIDB/04625/2020 (DOI: 10.54499/UIDB/04625/2020). Publisher Copyright: © 2024 by the authors.Electrochromic glazing alters its optical properties in the absence/presence of an electrical charge, varying from clear to dark to control daylighting and solar heat gains. This study aims to evaluate the impact of an electrochromic glazing, with indoor glare or temperature control, on the energy performance and thermal and visual comfort of an office room under three European climates, using a calibrated simulation model. The novelty of the paper lies in its combined performance assessment, using different standards and metrics. The results showed reduced climatization energy requirements with temperature control, but significantly increased artificial lighting energy use. Glare control achieved useful illuminance levels during 74–80% of working hours. Concerning temperature control, working hours within thermal comfort increased (21–43%) under a free-float regime. Moreover, the performance of this glazing was compared to that of a clear glazing with/without a reflective film and a thermochromic glazing for different solar orientations. The electrochromic glazing with glare control showed the highest energy savings (14–36%) for a western orientation, and the lowest negative impact on daylighting for a northern orientation. The best glare reduction was achieved with the reflective film. Considering the free-float regime, the electrochromic glazing, with temperature control, showed the highest increase in working hours within thermal comfort (6–9%) for a western orientation.publishersversionpublishe

Experimental analysis of the impact of photochromic glazing on indoor thermal and luminous conditions

The authors would like to thank the occupants of the office rooms (DEM-IST) for supporting the study. The authors gratefully appreciate the technical support given by the IMPERSOL Company. The authors would like to express their gratitude to CERIS (Civil Engineering Research and Innovation for Sustainability) research unit of IST-ID (Association of Instituto Superior T\u00E9cnico for Research and Development). The first author wishes to acknowledge the support of FCT (Fundação para a Ciência e a Tecnologia) PhD Grant FCT PD/BD/150576/2020 (DOI: 10.54499/PD/BD/150576/2020). The authors gratefully thank FCT for funding CERIS research unit through UIDB/04625/2020 (DOI: 10.54499/UIDB/04625/2020). Publisher Copyright: © 2024 The Author(s)The application of films on conventional glazing aims at increasing the glazing performance by reducing energy needs and increasing indoor comfort. Photochromic films in particular can alter their optical properties due to a chromatic change in response to solar radiation, allowing for reduced glare levels and solar heat gains. However, despite the potential of application, this refurbishment solution is still poorly explored. Therefore, the main purpose of this work was to experimentally evaluate the thermal and luminous performance of a double glazing with and without a photochromic film installed, using two office rooms in Lisbon as case study. An extended field experimental campaign was conducted simultaneously in both offices, where temperature, solar radiation and illuminance levels were collected. The key contribution and novelty of this research lies on the experimental assessment of the thermal and visual comfort conditions with the photochromic film under real-occupancy. Even though the photochromic film significantly increased the surface temperatures of the glazing, the indoor air temperature was not negatively affected, with an increase up to 14 % of working hours with comfortable temperature during the heating period. Illuminance levels on vertical/horizontal plane were reduced by 24/36 % in the presence of the photochromic film, when compared to the clear glazing without film, resulting in an increase of 7 % of working hours with useful illuminance during the heating period, and large areas in the office room with imperceptible daylight glare levels when facing the glazing system. The impact of the film was less noticeable during the cooling period.publishersversionpublishe

Small-scale field study of window films’ impact on daylight availability under clear sky conditions

Daylight illuminance levels and their spatial distribution are important design elements to achieve indoor visual comfort conditions and sustainability in buildings during the operation stage. While a proper daylighting scheme increases the efficiency of the building, the excessive use of glazed surfaces can contribute to thermal and visual discomfort, hence increasing the cooling demand and use of artificial lighting. Solar control film (SCF) is a self-adhesive thin film that can be applied on glazing systems of existing buildings for retrofitting purposes to modify thermal and optical properties of the glass substrate. This paper analyses experimentally the impact of single glazing with different SCFs on the indoor illuminance levels and respective distribution on horizontal work plane by comparing the measured absolute values and the useful daylight illuminance metric. Field experiments using a small scale model with the glazing oriented to the south, in Lisbon, were performed for a 6 mm clear glass and four different SCFs applied on the external surface of the glass, under clear sky conditions during summer and winter solstice at 9h00, 12h00, and 15h00. The results show that all SCFs reduced the indoor illuminance, which demonstrate their potential for glazing refurbishment when indoor visual discomfort occurs in buildings.FCT - Fundação para a Ciência e a Tecnologia (PD/BD/127848/2016

Synergistic effect of fibres on the physical, mechanical, and microstructural properties of aerogel-based thermal insulating renders

There is an increasing demand for highly efficient thermal insulating materials in buildings. This study presents a novel solution incorporating nanomaterials, such as silica aerogel, which can achieve low thermal conductivity values (below 0.030 W m-1 K-1) in renders. A key challenge of using aerogels is their low mechanical strength and high capillary water absorption. Here we describe a novel approach employing fibres which mitigates against some key properties which are decreased as a consequence of using aerogel. The incorporation of aramid (0.50%), sisal (0.10%), and biomass (0.10%) fibres (by total volume) was evaluated experimentally in terms of physical, mechanical, and microstructural properties. A synergistic effect between the fibres and aerogel increased mechanical resistance and a reduction in the capillary water absorption, when compared to the reference render (without fibres), whilst maintaining the low thermal conductivity. However, these properties depended significantly on whether the fibres were synthetic or organic. This study is important as it demonstrates that aerogel-based fibre-enhanced thermal renders can contribute to higher energy efficiency in both new construction and retrofitting. The use of these materials will have a direct positive impact on addressing the climate crisis

Synergistic effect of fibres on the physical, mechanical, and microstructural properties of aerogel-based thermal insulating renders

There is an increasing demand for highly efficient thermal insulating materials in buildings. This study presents a novel solution incorporating nanomaterials, such as silica aerogel, which can achieve low thermal conductivity values (below 0.030 W m-1 K-1) in renders. A key challenge of using aerogels is their low mechanical strength and high capillary water absorption. Here we describe a novel approach employing fibres which mitigates against some key properties which are decreased as a consequence of using aerogel. The incorporation of aramid (0.50%), sisal (0.10%), and biomass (0.10%) fibres (by total volume) was evaluated experimentally in terms of physical, mechanical, and microstructural properties. A synergistic effect between the fibres and aerogel increased mechanical resistance and a reduction in the capillary water absorption, when compared to the reference render (without fibres), whilst maintaining the low thermal conductivity. However, these properties depended significantly on whether the fibres were synthetic or organic. This study is important as it demonstrates that aerogel-based fibre-enhanced thermal renders can contribute to higher energy efficiency in both new construction and retrofitting. The use of these materials will have a direct positive impact on addressing the climate crisis

Analise Dinâmica do Desempenho Energético de um Envidraçado Termocrómico em Diferentes Zonas Climáticas de Portugal

Highly glazed facades are usually responsible for significant heat exchanges that increase climatization energy needs. Thermochromic glazing, an innovative glazing solution, can autonomous and reversibly alter its properties depending on the temperature of the thermochromic layer laminated between the external glass panes, promoting the reduction of thermal gains and the increase of indoor comfort and energy efficiency. This study aims at assessing the energy performance of a thermochromic glazing against a conventional static glazing with and without a reflective solar control film, considering an individual office room oriented southeast as case study. A dynamic simulation, previously calibrated with experimental data, was used to compute the monthly and yearly energy needs (heating and cooling) and energy use (climatization and artificial lighting) with the different glazing solutions installed in the cities of Braganza, Lisbon and Faro, representative of different climate zones of Portugal. A reduction up to 65% of the cooling energy needs was obtained with the thermochromic glazing. The dynamic behaviour of the thermochromic glazing reduced indoor daylight levels, consequently increasing artificial lighting energy use. However, it was possible to achieve a reduction up to 50% of the total energy use (climatization and artificial lighting) with the dynamic glazing.Fachadas de edifícios com grandes áreas envidraçadas tendem a promover trocas térmicas significativas que resultam em necessidades energéticas para climatização elevadas. Os envidraçados termocrómicos podem alterar de forma autónoma e reversível as suas propriedades térmicas e óticas dependendo da sua temperatura, promovendo a mitigação de ganhos térmicos e a melhoria de condições de conforto interior e eficiência energética. Este estudo tem como objetivo analisar o desempenho energético de um envidraçado termocrómico instalado num gabinete orientado a sudeste. Para esse fim, foi utilizado um modelo de simulação dinâmica, anteriormente calibrado com dados experimentais, para avaliar o desempenho energético anual do vidro termocrómico comparativamente ao de um envidraçado convencional incolor com e sem uma película refletora de controlo solar. As necessidades energéticas (aquecimento e arrefecimento) e o consumo energético (aquecimento, arrefecimento e iluminação artificial) foram obtidos para as diferentes soluções de envidraçados nas cidades de Bragança, Lisboa e Faro, representativas de diferentes zonas climáticas de Portugal. Com o envidraçado termocrómico obteve-se uma redução significativa, até 65%, das necessidades energéticas para arrefecimento. Apesar do comportamento dinâmico do envidraçado termocrómico e da diminuição das condições de iluminação natural do gabinete, foi possível obter uma redução do consumo anual energético total até 50%

Studies in 3-oxy-assisted 3-aza Cope rearrangements

On thermolysis appropriately substituted N-silyloxy-N-allyl enamines undergo smooth 3,3-sigmatropic rearrangments to the corresponding N-silyloxy imino ethers

In-Situ Tests on Silica Aerogel-Based Rendering Walls

In this paper, two aerogel-based renders are characterized based on in-situ testing of walls prototypes. The in-situ tests to assess the mechanical performance are: pull-off, surface impact tests and compressive strength on collected samples. The physical performance includes the water resistance and thermal conductivity coefficient. The tests carried out to assess water-resistance are: Karsten tube, moisture meter and capillary water absorption of collected samples. The thermal performance was tested based on infrared thermography and thermal conductivity transient method. The combination of these in-situ tests allowed a better performance characterization of the aerogelbased renders and characterized the applied renders. These results were carried out under two national research projects (Nanorender and P2020 PEP)

Durability assessment of external thermal insulation composite systems in urban and maritime environments

External Thermal Insulation Composite Systems (ETICS) are multilayer solutions which provide an enhanced thermal performance to the building envelope. However, significant anomalies can be detected on ETICS facades, in some cases shortly after the application of these systems. This study intends to evaluate and compare the durability of six commercially available ETICS after two years of outdoor exposure at both urban and maritime conditions in Portugal. The systems were characterized by means of non-destructive testing (i.e., visual and microscopic assessment, water transport properties, thermal conductivity, surface roughness), thus allowing to evaluate the performance loss throughout natural aging. The bio-susceptibility and aesthetic properties (color and gloss) were also investigated. Results showed that the performance and durability of the complete system is significantly affected by the rendering system formulation. The lime-based specimens obtained the highest rate of mold development after one year of aging in a maritime environment, becoming considerably darker and with lower surface gloss. Fungal analysis of this darkish stained area indicated the presence of mold species of the genera Alternaria, Didymella, Cladosporium and Epicoccum, and yeasts of the genera Vishniacozyma and Cystobasidium. An increase of both capillary water absorption and water vapor permeability was also registered for the aged lime-based specimens. Acrylic-based systems obtained lower capillary water absorption after aging and greater dirt deposition on their surfaces, especially in urban conditions. These systems had also higher color variation and surface gloss decrease and slightly higher mold growth, when compared with those aged in a maritime environment. Finally, no mold growth was detected on the silicate-based specimens after two years of aging. However, these specimens obtained higher capillary water absorption and lower vapor permeability after aging, possibly leading to moisture accumulation within the system. Results contribute towards the development of ETICS with enhanced performance and durability.info:eu-repo/semantics/publishedVersio