added 4 research items
Tyre4BuildIns - Recycled tyre rubber resin-bonded for building insulation systems towards energy efficiency
Plaster is one of the most used and studied materials in the building process. This paper shows the result of the characterisation of a new plaster-based material enlightened and reinforced with polymers and end-of-life tyres’ recycled materials. As far as end-of-life tyres are a common waste item, this paper offers new recycling possibilities, as well as significant improvements in new building materials. Mechanical, thermal conductivity, sound absorption, fire reaction and environmental impact are studied and analysed. Three different end-of-life tyres’ recycled materials are used, two size rubber and textile fibres. A significant density reduction up to 17% was achieved mainly due to end-of-life materials lower density. Two thermal conductivity measurement methods, heat flux meter and guarded hot plate, were conducted and then compared. A 20% improvement with respect to the reference was achieved in those samples with textile fibre. The two methods’ measurements got a 1% difference in all samples analysed except textile fibre. Thus, this allowed to validate these methods and assure these measurements. Sound absorption was also measured. These materials reached α = 0.32 in high frequencies. Performance in low frequencies were lower. Fire tests led to no ignition results and no fire propagation. Finally, a basic global warming potential impact study based on environmental product declaration (EPD) is conducted. The most relevant result of this study is the potential 20–34% reduction of CO2 emissions with the elaboration of these composites.
Thermal bridges may have a significant prejudicial impact on the thermal behavior and energy efficiency of buildings. Given the high thermal conductivity of steel, in Lightweight Steel Framed (LSF) buildings, this detrimental effect could be even greater. The use of thermal break (TB) strips is one of the most broadly implemented thermal bridge mitigation technics. In a previous study, the performance of TB strips in partition LSF walls was evaluated. However, a search of the literature found no similar experimental campaigns for facade LSF walls, which are even more relevant for a building’s overall energy efficiency since they are in direct contact with the external environmental conditions. In this article the thermal performance of ten facade LSF wall configurations were measured, using the heat flow meter (HFM) method. These measurements were compared to numerical simulation predictions, exhibiting excellent similarity and, consequently, high reliability. One reference wall, three TB strip locations in the steel stud flanges and three TB strip materials were assessed. The outer and inner TB strips showed quite similar thermal performances, but with slightly higher thermal resistance for outer TB strips (around +1%). Furthermore, the TB strips were clearly less efficient in facade LSF walls when compared to their thermal performance improvement in load-bearing partition LSF walls.
Hydrophobic rubber-silica aerogel panels (21.5 × 21.5 × 1.6 cm3) were fabricated from silica and rubber sols and reinforced with several fiber types (recycled tire textile fibers, polyester blanket, silica felt, glass wool). A recycled rubber sol was prepared using peracetic acid and incorporated for the first time in TEOS-based sol-gel chemistry. The composites exhibited good thermal stability up to 400 °C and very low thermal conductivity, in the superinsulation range when using polyester fibers (16.4 ± 1.0 mW.m−1.K−1), and of 20–30 mW.m−1.K−1 for the remaining fibers. They could also endure cyclic compression loads with near full recovery, thus showing very promising properties for insulation of buildings.
The thermal performance of Lightweight Steel Framed (LSF) walls could be strongly compromised due to steel’s high thermal conductivity and their related thermal bridges. In this paper, the performance of bio-based (pine wood) and recycled (rubber–cork composite) Thermal Break Strip (TBS) materials, to mitigate the thermal bridge effect originated by steel profiles in LSF partition walls, is evaluated. This assessment was achieved by measurements under controlled laboratory conditions and by predictions using some numerical simulation models. Regarding the measurements, two climatic chambers (cold and hot) were used to impose a nearly constant temperature difference (around 35 °C), between the LSF partition test samples’ surfaces. To measure the overall surface-to-surface thermal resistance (-value) of the evaluated LSF wall configurations, the Heat Flow Meter (HFM) method was used. Moreover, the measured values were compared with the calculations by 2D (THERM models) and 3D (ANSYS models) numerical simulations, exhibiting an excellent agreement (less than ±2% difference). Three TBS locations and three materials are evaluated, with their thermal performance improvement compared with a reference interior partition LSF wall, having no TBS. The top performance was accomplished by the aerogel super-insulating TBS material. The bio-based material (pine wood) and the recycled rubber–cork composite present quite similar results, with a slight advantage for the pine wood TBSs, given their higher thickness. Considering the TBS location, the inner and outer side present comparable performances. When using TBSs on both sides of steel profile flanges, there is a relevant thermal performance improvement, as expected. The thickness of the TBS also presents a noteworthy influence on the LSF partition thermal resistance.
The reduction of unwanted heat losses across the buildings’ envelope is very relevant to increase energy efficiency and achieve the decarbonization goals for the building stock. Two major heat transfer mechanisms across the building envelope are conduction and radiation, being this last one very important whenever there is an air cavity. In this work, the use of aerogel thermal break (TB) strips and aluminium reflective (AR) foils are experimentally assessed to evaluate the thermal performance improvement of double-pane lightweight steel-framed (LSF) walls. The face-to-face thermal resistances were measured under laboratory-controlled conditions for sixteen LSF wall configurations. The reliability of the measurements was double-checked making use of a homogeneous XPS single panel, as well as several non-homogeneous double-pane LSF walls. The measurements allowed us to conclude that the effectiveness of the AR foil is greater than the aerogel TB strips. In fact, using an AR foil inside the air cavity of double-pane LSF walls is much more effective than using aerogel TB strips along the steel flange, since only one AR foil (inner or outer) provides a similar thermal resistance increase than two aerogel TB strips, i.e., around +0.47 m2∙K/W (+19%). However, the use of two AR foils, instead of a single one, is not effective, since the relative thermal resistance increase is only about +0.04 m2∙K/W (+2%).
One strategy to increase energy efficiency of buildings could be the reduction of undesirable heat losses by mitigating the heat transfer mechanisms across the building envelope. The use of thermal insulation is the simplest and most straightforward way to promote thermal resistance of building elements by reducing the heat transfer by conduction. However, whenever there is an air cavity, radiation heat transfer could be also very relevant. The use of thermal reflective insulation materials inside the air gaps of building elements is likewise an effective way to increase thermal resistance without increasing weight and wall thickness. Some additional advantages are its low-cost and easy installation. In this work, the performance of a thermal reflective insulation system, constituted by an aluminium foil placed inside an air cavity between a double pane lightweight steel framed (LSF) partition, is experimentally evaluated for different air gap thicknesses, ranging from 0 mm up to 50 mm, with a step increment of 10 mm. We found a maximum thermal resistance improvement of the double pane LSF walls due to the reflective foil of around +0.529 m2∙°C/W (+21%). The measurements of the R-values were compared with predictions provided by simplified models (CEN and NFRC 100). Both models were able to predict with reasonable accuracy (around ±5%) the thermal behaviour of the air cavities within the evaluated double pane LSF walls.
An accurate thermal characterization of the envelope components is essential to achieve a reliable evaluation of thermal behaviour and energy efficiency of buildings. In lightweight steel-framed (LSF) building components, the major thermal performance concern is related to the unwanted significant thermal bridge effects originated by the high thermal conductivity of steel. The application of thermal break (TB) strips in the steel stud flanges is one of the most currently used thermal bridge mitigation strategies. In this paper the thermal performance of ten interior LSF walls configurations are measured, using the heat flow meter (HFM) method under laboratory-controlled conditions. Three TB strips materials and three TB locations (inner, outer and both sides of steel stud) are assessed and a comparison with the thermal performance of a reference wall without TB strips is made. Regarding the TB strips materials, it was found that the best thermal performance is achieved by aerogel, which is the material that presents the lowest thermal conductivity. Considering the TB strips location, the application on both sides of steel stud shows a relative significant thermal performance increase comparatively to the application on inner or outer side, presenting these last two configurations very similar performances.
Silica aerogels hold remarkable properties, particularly their translucence/transparency and extremely low thermal conductivity and density, for buildings thermal insulation purpose. Incorporated in composites or framing systems, they reduce the overall weight of the building envelope while increasing its thermal resistance, being especially valuable for energy-efficient retrofitting solutions, spanning from covering façades to window panes. This review presents the production process of silica aerogels in brief, their relevant properties regarding building’s needs, and a full survey of last years’ scientific achievements on silica aerogel-containing materials for buildings, such as panels, blankets, cement, mortars, concrete, glazing systems, solar collector covers, among others.
Energy production still relies considerably on fossil fuels, and the building sector is a major player in the energy consumption market, mainly for space heating and cooling. Thermal bridges (TBs) in buildings are very relevant for the energy efficiency of buildings and may have an impact on heating energy needs of up to 30%. Given the high thermal conductivity of steel, the relevance of TBs in lightweight steel framed (LSF) components could be even greater. No research was found in the literature for evaluating how important the size and shape of steel studs are on the thermal performance of LSF building elements, which is the main objective of this work. This assessment is performed for the internal partitions and exterior façade of load-bearing LSF walls. The accuracy of the numerical model used in the simulations was verified and validated by comparison experimental measurements. Three reference steel studs were considered, six stud flange lengths and four steel thicknesses were evaluated, and five flange indentation sizes and four indent filling materials were assessed, corresponding to a total of 246 modelled LSF walls. It was concluded that the -value decreases when the flange length and the steel studs’ thickness increases, being that these variations are more significant for bigger flange sizes and for thicker steel studs. Additionally, it was found that a small indentation size (2.5 or 5 mm) is enough to provide a significant -value increase and that it is preferable not to use any flange indentation filling material rather than using a poor performance one (recycled rubber).
A reliable evaluation of thermal behaviour and energy efficiency of buildings depends on the accurate thermal characterization of the envelope components. One of the most reliable methodologies to perform this thermal characterization is the measurements under laboratory-controlled conditions. The thermal performance assessment of lightweight steel-framed (LSF) building components exhibits particular additional challenges related to the strong thermal conductivity contrast between cavity insulation and steel frame materials, which may originate unwanted significant thermal bridge effects. The use of thermal break (TB) strips is one of the most currently used thermal bridge mitigation strategies. It was not found in the literature any experimental campaign for TB strips thermal performance evaluation in LSF elements. In this paper the thermal performance of twenty load-bearing (LB) and non-load-bearing (NLB) LSF walls configurations are measured, using the heat flow meter (HFM) method under controlled laboratory conditions. Three thermal break (TB) strip materials and three TB strip locations in the steel stud flanges are assessed. It was found that the inner and outer TB strips show very similar thermal performances, while double TB strips have a relative significant thermal performance increase. Aerogel was the best performance TB material, exhibiting a substantial improvement relatively to recycled rubber and cork/rubber composite TB strips. Furthermore, the TB strips performance was identical for the evaluated structural (LB) and non-structural (NLB) LSF walls.
Buildings are seeking renewable energy sources (e.g., solar) and passive devices, such as Trombe walls. However, the thermal performance of Trombe walls depends on many factors. In this work, the thermal behavior and energy efficiency of a Trombe wall in a lightweight steel frame compartment were evaluated, making use of in situ measurements and numerical simulations. Measurements were performed inside two real scale experimental identical cubic modules, exposed to natural exterior weather conditions. Simulations were made using validated advanced dynamic models. The winter Trombe wall benefits were evaluated regarding indoor air temperature increase and heating energy reduction. Moreover, a thermal behavior parametric study was performed. Several comparisons were made: (1) Sunny and cloudy winter week thermal behavior; (2) Office and residential space use heating energy; (3) Two heating set-points (20 °C and 18 °C); (4) Thickness of the Trombe wall air cavity; (5) Thickness of the thermal storage wall; (6) Dimensions of the interior upper/lower vents; (7) Material of the thermal storage wall. It was found that a Trombe wall device could significantly improve the thermal behavior and reduce heating energy consumption. However, if not well designed and controlled (e.g., to mitigate nocturnal heat losses), the Trombe wall thermal and energy benefits could be insignificant and even disadvantageous.
Resumo. O sistema de construção em LSF é rápido, limpo e flexível, mas os elementos de sua estrutura precisam ser adequadamente projetados e protegidos contra os efeitos das pontes tér-micas causadas pela elevada condutibilidade térmica do aço. É necessário entender como ocor-rem as transferências de calor através dos elementos construtivos de toda a envolvente da edi-ficação para que se possa reduzir a perda de calor através desses elementos e diminuir o valor do coeficiente de transmissão térmica (valor de Neste trabalho foram realizadas simulações numéricas para avaliar diferentes configurações de paredes interiores em LSF (entre espaços úteis e não úteis). Vários parâmetros foram avaliados separadamente para que fosse possível medir sua influência no valor total de da parede. 1. Introdução Os edifícios são responsáveis por cerca de 40% do total de energia consumida e cerca de 36% das emissões de CO2 na Europa.  Os principais fatores com influência no consumo de energia de um edifício têm relação direta com as propriedades e forma da envolvente do edifício, o seu funcionamento, o comportamento dos seus ocupantes e o clima do local onde está situado    . O setor de edifícios inclui os edifícios residenciais, comerciais, institucionais e outros não especificados. O uso de energia em edifícios abrange o aquecimento e arrefecimento de ambi-ente, aquecimento de águas sanitárias, iluminação, eletrodomésticos e equipamentos de cozinha .Normalmente, uma parede em LSF usada como divisória interna é composta pelos seguintes elementos: (1) estrutura leve em perfis de aço enformados a frio; (2) painéis de revestimento, como gesso e OSB ("Orientated Strand Board"); (3) materiais de isolamento térmico e acús-tico, como lã mineral, que preenchem a cavidade existente entre os perfis verticais .
This paper provides a kick-off presentation of the project "Tyre4BuildIns"-Recycled tyre rubber resin-bonded for building insulation systems towards energy efficiency. The main goal of this project is to develop a new cost-effective eco-friendly thermal insulation material, that will be used mainly, but not exclusively, as a thermal b reak in Lightweight Steel Framed (LSF) building structures, taking advantage of recycled tyre rubber as a main raw-material and mixed it with an advanced state of the art material within a resin-bonded composite. It is planned to evaluate and optimize the performance of this new composite insulation at material level and building elements level (e.g. walls) in order take maximum thermal and acoustic advantage of it. It will be also assessed its environmental impacts and costs from a life cycle perspective. "Tyre4BuildIns" is a three years duration challenging project involving researchers from different scientific backgrounds, namely civil and chemical engineering from University of Coimbra (UC),
Given its economical, functional and environmental advantages, Lightweight Steel Frame (LSF) construction is gaining market share, particularly for low-rise residential buildings, relatively to traditional concrete structure and masonry brick walls construction. However, these LSF elements need to be well designed and protected against undesired thermal bridges caused by the steel high thermal conductivity. To reduce energy consumption in buildings it is necessary to understand how heat transfer happens in every kind of walls and their configurations, and to adequately reduce the heat loss through them by decreasing its thermal transmittance (U-value). In this work, numerical simulations are performed to assess different setups for LSF exterior facade walls. Several parameters, such as: (1) thickness of steel studs; (2) clearance between studs; thermal break strips: (3) thickness and (4) material; (5) configuration of internal sheathings panels, and; (6) thickness of EPS external thermal insulation composite system (ETICS), were evaluated separately to measure their influence on the wall overall U-value. The existence of an ETICS continuous thermal insulation on the outer side reduces itself the heat flux through the wall, particularly through the steel frame, resulting on a lower wall U-value and decreasing the importance of other evaluated parameters. In fact, the major and the minor U-value increment was found changing the thickness of the EPS insulation ETICS layer, i.e. an augment of +79.0% when there is no EPS (0.0 mm thick) and a decrease of-19.2% for 80 mm EPS thickness. Notice that the reference wall has 50 mm of EPS ETICS. Decreasing the steel thickness (1.5 mm) to 0.6 mm allowed to reduce the U-value down to only-3.3% (-0.009 W/(m 2 .K)). When changing the distance between the vertical studs from 600 mm to half (300 mm), doubling the amount of steel, the U-value increased only +17.0% (+0.047 W/(m 2 .K)). The use of aerogel thermal break strips with different thicknesses (up to 10 mm) allowed to reduce the U-value down to-10.1% (-0.028 W/(m 2 .K)). The use of different inner sheathing panels (GPB, OSB and XPS) allowed to obtain a U-value variation down to-7.2% (-0.020 W/(m 2 .K)) for the XPS/GPB panels. Topic: Advanced facade design, technology and materials.
Light steel framed (LSF) construction is becoming widespread as a quick, clean and flexible construction system. However, these LSF elements need to be well designed and protected against undesired thermal bridges caused by the steel high thermal conductivity. To reduce energy consumption in buildings it is necessary to understand how heat transfer happens in all kinds of walls and their configurations, and to adequately reduce the heat loss through them by decreasing its thermal transmittance (U-value). In this work, numerical simulations are performed to assess different setups for two kinds of LSF walls: an interior partition wall and an exterior facade wall. Several parameters were evaluated separately to measure their influence on the wall U-value, and the addition of other elements was tested (e.g., thermal break strips) with the aim of achieving better thermal performances. The simulation modeling of a LSF interior partition with thermal break strips indicated a 24% U-value reduction in comparison with the reference case of using the LSF alone (U = 0.449 W/(m2.K)). However, when the clearance between the steel studs was simulated with only 300 mm there was a 29% increase, due to the increase of steel material within the wall structure. For exterior facade walls (U = 0.276 W/(m2.K)), the model with 80 mm of expanded polystyrene (EPS) in the exterior thermal insulation composite system (ETICS) reduced the thermal transmittance by 19%. Moreover, when the EPS was removed the U-value increased by 79%.