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Highlights • Experimental campaign on industrial and experimental thermal renders. • Formulations with EPS, cork, and several binders and admixtures. • Physical properties at fresh and hardened states. • Standard and non-standard specimens and brick-render models. Abstract Nowadays, there is a concern in getting buildings with reduced environmental impact and improved thermal and energy performance. The need to use new technologies to comply with the thermal requirements has been driven by the regulation for buildings. With this goal in mind, the use of thermal insulation systems on facades has increased. In this context, renders with high thermal insulation performance have recently emerged on the market. This paper discusses the physical characteristics of four industrial thermal renders, comparing with two experimental render mixtures in which sand is replaced by aggregates with thermal insulating properties (EPS and cork) without any additions or admixtures. It is noticed a need to incorporate high ratios of aggregate with thermal characteristics to achieve thermal insulation renders, affecting other physical properties of the renders at both fresh (workability, air content and bulk density) and hardened (water absorption under low pressure, capillary, dry bulk density, open porosity and drying capacity) states. [ABSTRACT FROM AUTHOR]

In order to fulfil the increasing demands of indoor comfort and energy efficiency requirements of buildings, innovative materials with good thermal properties have been developed, such as thermal insulating mortars with incorporation of lightweight aggregates and nanomaterials. In the present work, the thermal conductivity of thermal insulating mortars, with EPS and silica-based aerogel, were evaluated for hardened state (28 days of curing), dry state and different moisture content values. Moreover, several methods were performed: two steady-state and two transient methods. For comparison purposes, all of the obtained thermal conductivity values were converted to 23 °C. It is concluded that the results are highly dependent on the temperature and the moisture content of the samples, and the measuring method. This study also shows that the thermal conductivity presents values with variations up to 21% and 14%, with different methods for the mortar’s formulations with and without silica aerogel. It is also concluded that the thermal conductivity evaluation methods have differences regarding the sample’s size, testing time, operation and apparatus’ accuracy and reproducibility. This must be considered, particularly when developing innovative materials, where the material availability or the measurement range of the method can limit the thermal conductivity measurement. [ABSTRACT FROM AUTHOR]

The growing European interest on building sustainability has driven the establishment of the 2012/27/UE Directive. Mortars with thermal conductivity lower than 0.2 W/m·K (thermal mortars) can have an important role in the energy efficiency of buildings. The thermal conductivity is a fundamental parameter to characterize the hygrothermal performance of mortars. Nevertheless, its measurement is complex due to its large dependency on several factors and its dynamic behaviour. In the present paper, an experimental campaign is carried out to evaluate the influence of the moisture content on the thermal conductivity of 17 thermal mortars. Moreover, correlations between thermal conductivity analytically estimated from standards and experimentally measured are assessed. The results showed that the thermal conductivity is significantly dependent on the moisture content. However, most of the building standards use fixed conductivity values for normalized conditions. Therefore the discussion of relevant influence factors on thermal conductivity of thermal mortars can help designers and professionals to evaluate the hygrothermal performance of in-service buildings facades with thermal mortars, when subjected to real exposure conditions. [ABSTRACT FROM AUTHOR]

In recent years, Energy Performance Building Directives have been published and adopted by all EU member states in order to promote the improvement of the energy performance of buildings within the EU, and thus coping with the growing comfort needs and consequent increase in energy consumption for space heating and cooling. Structural lightweight aggregate concrete (SLWAC), due to its thermal properties, presents itself as an alternative to normal weight concrete (NWC) to reduce the thermal bridging effects as well as the building energy needs to maintain thermal comfort levels in buildings. In this paper, the potential of SLWAC to improve the energy performance of buildings was assessed. An experimental study was carried out in order to determine the thermal properties of five different concrete mixtures, four SLWAC and a reference NWC for comparison purposes. These thermal properties were then used in the two-dimensional heat transfer program Therm and in the whole-building energy simulation program EnergyPlus to assess the impact of SLWAC on the thermal bridge heat losses and building energy needs of a case study. Results showed that SLWAC can improve the energy efficiency of buildings and thus be an attractive alternative to the use of the traditional NWC. [ABSTRACT FROM AUTHOR]

This paper quantifies green roofs energy savings which is a challenging topic, namely in Mediterranean climate with distinct heating and cooling seasons. The thermal behavior of a green roof case study in Lisbon, Portugal, was assessed through an experimental campaign during heating and cooling periods of the year of 2013. These experimental results were then used to calibrate a building energy simulation in EnergyPlus. After validation, the numerical model was used to compare the energy performance of intensive, semi-intensive and extensive green roofs. The three green roof types lead to similar heating energy needs but extensive green roof solution shows higher cooling energy needs than semi-intensive and intensive ones, of 2.8 and 5.9 times more, respectively. Furthermore, the performance of each type of green roof and different insulation properties was compared to traditional roof solutions. With no thermal insulation, extensive green roofs require 20% less energy use than black roofs and show a similar annual behavior than white roofs. Semi-intensive and intensive green roofs energy use is 60–70% and 45–60% lower than black and white roofs, respectively. Well insulated roofs do not take full advantage of evapotranspiration cooling effects, which is particularly noticeable when comparing with high reflective white roofs. [ABSTRACT FROM AUTHOR]

Highlights: [•] The concrete–steel bond of LWC is characterized for different failure mechanisms. [•] In splitting, the bond strength of LWC was 70% that of normal concrete. [•] The bond strength of LWC can be more than twice that of NWC of equal compressive strength. [•] It has been shown that the normative expressions proposed for LWC may be too unrealistic. [•] A new approach for estimating the LWC bond strength has been suggested. [ABSTRACT FROM AUTHOR]

Highlights: [•] The ventilation of a room with an atmospheric-vent water heater is investigated. [•] An airflow model for two storeys sharing a common chimney is simulated in EnergyPlus. [•] The air infiltration from different air permeability classes of windows is estimated. [•] Room airflows are compared with the stoichiometric air requirements. [•] The energy performance of a room with an atmospheric-vent water heater is assessed. [ABSTRACT FROM AUTHOR]

• Pre-walls system: two pre-cast concrete panels and a cast-in-situ concrete core. • High performance pre-cast concrete and low-cement lightweight cast-in-situ concrete. • Thermophysical properties of concretes for dry, hygroscopic and capillary ranges. • An application study of the pre-walls system to a swimming pool was carried out. • Low-cement lightweight concrete in the core improve the system thermal performance. An innovative system of pre-cast high performance concrete pre-walls, combined with low-cement cast-in-situ lightweight concrete core, is studied experimentally from the standpoint of the thermophysical properties of the concrete compositions under various hygroscopic conditions. Thermal conductivity, volumetric heat capacity and thermal diffusivity are experimentally determined, by a transient method, for eight concrete compositions in the dry state, hygroscopic and over-hygroscopic ranges. The incorporation of lightweight aggregates in the concrete mixture allowed to reduce the thermal conductivity (up to 53%) and thermal diffusivity (up to 41%), in comparison to normal weight concrete. The moisture content, regardless of the composition of the concrete, impacts negatively the thermal performance, with a rise of both thermal conductivity and diffusivity, which was also captured by analytical expressions. An application study of the pre-walls system to a swimming pool showed reductions of thermal conductance of up to 38% when combining high mechanical performance concrete in the pre-walls with lightweight aggregate concrete with high thermal performance in the core. These results highlight the importance of assessing thermophysical properties in service conditions, with the moisture content effect included, and selecting the types of concrete in composite pre-walls systems to enhance both mechanical and thermal performance. [ABSTRACT FROM AUTHOR]

Abstract: In this paper the compressive strength of a wide range of structural lightweight aggregate concrete mixes is evaluated by the non-destructive ultrasonic pulse velocity method. This study involves about 84 different compositions tested between 3 and 180days for compressive strengths ranging from about 30 to 80MPa. The influence of several factors on the relation between the ultrasonic pulse velocity and compressive strength is examined. These factors include the cement type and content, amount of water, type of admixture, initial wetting conditions, type and volume of aggregate and the partial replacement of normal weight coarse and fine aggregates by lightweight aggregates. It is found that lightweight and normal weight concretes are affected differently by mix design parameters. In addition, the prediction of the concrete’s compressive strength by means of the non-destructive ultrasonic pulse velocity test is studied. Based on the dependence of the ultrasonic pulse velocity on the density and elasticity of concrete, a simplified expression is proposed to estimate the compressive strength, regardless the type of concrete and its composition. More than 200 results for different types of aggregates and concrete compositions were analyzed and high correlation coefficients were obtained. [Copyright &y& Elsevier]

Shading devices are used to reflect direct sunlight, reduce glare and prevent overheating. A correctly designed shading system will strongly influence the entire building energy consumption, peak loads and indoor comfort. The use of the venetian blinds is particularly common due to its relatively low cost and high versatility. The present study focuses on the algorithms for calculating both short-wave (solar) and long-wave (infrared) transmittance, absorptance and reflectance of the venetian blinds. The model is based on the net radiation method, allows for different slat discretization schemes and is suitable for integration into the building energy simulation tools. Once the effective optical properties are computed, the system can be regarded as an additional layer in a multilayer glazing system. Computed blind solar transmittance has been compared with other numerical models and in situ experimental results. A general good agreement has been found, except in cases where incident radiation is mostly diffuse. In this study, the effect of different design parameters on effective optical properties of the venetian blinds is also investigated: (a) the sun profile angle, (b) the slat angle and (c) the venetian blind geometry. Moreover, the effect of the discretization of each slat is examined. [ABSTRACT FROM AUTHOR]

Glazings systems are responsible for significant building gains and losses regarding energy and thermal loads. Thus, current research has converged on finding glazing solutions that minimize heating, cooling, and lighting needs. One example of innovative glazing systems is thermochromic glazings. These glazings change their optical and thermal properties according to their surface temperatures by darkening at higher temperatures and consequently decreasing visible and solar transmittance. These property transitions have an impact not only on the heating and cooling needs of a building but also on the electric lighting needs. This research aims to study the impact that different switching temperature ranges and thermochromic coating transmittance values have on the energy use of an office room in different climates. This is accomplished with the annual energy simulation for heating, cooling, and electric lighting energy use of an office with a thermochromic glazing system in two different climates. A multi-objective optimization process is integrated to minimize the office's thermal, lighting, and total energy use according to the thermochromic glazing transition temperatures and transmittances. Optimization results show highly conflicting values between the office room's electric lighting and climatization energy use, showing that electric lighting energy use can increase up to 200% with low transition temperatures. Additionally, optimum solutions show improvements of 15% in total energy use against one off-the-market thermochromic glazing. • Theoretical properties of a thermochromic glazing system are optimized. • Optimization and Machine Learning techniques are used to perform the optimization. • Lighting energy use increased up to 200% for minimum climatization energy use. • Improvements of 15% in energy use against one off-the-market thermochromic glazing. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the results of a program of wind tunnel model tests on pressure distributions for irregular-plan shapes (L- and U-shaped models). The experiments were carried out in a closed-circuit wind tunnel and a multi-channel pressure measurement system was used to measure mean values of loads on 1:100 scale models. The same tests were carried out on a cube-shaped model as an experimental validation. The effectiveness of the model shape in changing the surface pressure distributions is assessed over an extended range of wind directions. The experimental data for the L- and U-shaped models showed different wall pressure distributions from those expected for single rectangular blocks. Furthermore, a Computational Fluid Dynamics (CFD) code was used to illustrate some particular cases and to provide a better understanding of the flow patterns around these irregular-plan models and of the pressure distributions induced on their faces. Computed pressure coefficients have also been compared with wind tunnel results for normal and oblique wind incidence. A general good agreement has been found for normal wind incidence whereas some differences have occurred for other directions. [Copyright &y& Elsevier]

The increasing requirements in building thermal and energy performance standards and the need to design nearly zero-energy buildings, while still enhancing the indoor comfort conditions, have led to a demand for more efficient thermal building envelope solutions. Knowledge concerning the performance of building thermal envelope solutions and the existing design support tools, such as building performance simulation, is crucial for stakeholders to make informed decisions with respect to the definition and implementation of energy efficient strategies for new and refurbished buildings. The results of U-value of the windows through actual physical experiments show that, in the case of aluminum windows, the U-value corresponding to Grade 3 (1.4-2.1 W/m SP 2 sp -K) was as high as about 60%, whereas in PVC windows, Grade 3 (U-value of 1.4-2.1 W/m SP 2 sp -K) accounted for about 35%, and Grade 2 (U-value of 1.0-1.4 W/m SP 2 sp -K) for about 29%. Moreover, component-level and whole building numerical simulations were performed under cooling-dominated and heating-dominated climate conditions to investigate the energy benefits of applying the TAC system to the external walls of a typical, single-family residential building. [Extracted from the article]

Highlights • The impact of the urban context on buildings' solar energy potential was assessed. • 3D GIS was used to build a city block in Lisbon and surrounding urban context. • Three solar radiation tools associated with 2.5D and 3D approaches were used. • Influence of context size, relief, built surroundings and claddings were evaluated. • The mean effect of relief and built surroundings over the city block was about 30%. Abstract Buildings are responsible for 40% of energy consumption and 36% of CO ₂ emissions in the European Union. To bring these levels down, governments are striving to promote a more efficient use of energy resources and an increase adoption of renewable energy technologies, as photovoltaic panels and solar collectors on the building envelopes. To fully exploit the potential of these technologies, a detailed analysis of the incident solar radiation on buildings roofs and facades is mandatory taking into account the geographical and urban environments. Three solar radiation tools, in association with two different modelling approaches (2.5D and 3D) handled by a 3D GIS tool, were applied to a city block of downtown Lisbon for both the winter and summer solstices and for different levels of detail of the surrounding context. The study showed that both built surroundings and topographic relief have an important impact on solar potential of buildings in urban areas. An average difference of about 30% in the results was observed between the simulations with and without the geographical and the urban environments included. The study also showed that the 3D approach has high potential to fully evaluate solar access in complex urban layouts, for accounting the irradiation of all sun-exposed surfaces of the buildings. [ABSTRACT FROM AUTHOR]

The incorporation or the replacement of materials in buildings may decrease the energy use during the operational stage but increase the embodied energy in a building's life cycle. In this study, three different solar control films (SCFs A, B and C) with application on the existing windows of a building are investigated through an energy, environmental and economic perspective over a defined life cycle period. The full replacement of the existing window with a new one is also analyzed as an alternative retrofitting solution. Retrofitting solutions with higher light-to-solar gain ratios showed higher energy savings during the use stage by decreasing the solar gains in a higher proportion than the decrease of the visible transmittance. The best retrofitting solution, SCF C, showed a life cycle energy (LCE) (embodied plus operational energy) and a carbon footprint of 4447 MJ/m2/40 y and 380 kgCO 2 eq/m2/40 y, respectively, whereas the least performant solution, new window, showed a LCE 1.5 times higher than the average of the three SCFs. The higher LCE value of the new window was found to be related to the higher value of the embodied energy when compared to that of the three SCFs (∼9 times higher than the average of the films). • Energy, environmental and economic study of two alternative window retrofit solutions. • Retrofit scenarios: installation of films (SCFs) or full replacement with new window (NW). • Solutions with higher light-to-solar gain ratios (τ vis /g) showed higher operational energy savings. • Embodied energy (EE) of NW is nine times higher than the EE of SCFs. • Life cycle energy (LCE) of NW 1.5 times higher than the LCE of SCFs. [ABSTRACT FROM AUTHOR]

• An experimental study of a new innovative solar passive retrofit solution is studied. • The new design enables the heavy structure of the building to absorb solar radiation. • Proposed system may be used in combination with the traditional ETICS. • Indoor temperature may be increased in the range of 2-5ºC above outdoor in winter. • Results also imply that the system may provide heat gains throughout the day. The structural components of load-bearing concrete frame buildings, such as concrete beams and columns, are critical elements of the facades which often act as a thermal bridge. To reduce the impact of structural thermal bridge areas in non-retrofitted Portuguese residential buildings, a new innovative solar passive retrofit solution, named Solar Bridge Retrofit System (SBRS), is proposed. This concept relies on the principles of unvented Trombe wall systems and consists in using an external transparent skin in front of the structural areas of the envelope in combination with the traditional ETICS in the remaining area. Contrary to the traditional Trombe walls, this innovative design enables the heavy structure of the building to absorb solar radiation and conduct the heat slowly inward or to the adjacent structure. To evaluate the thermal performance of the SBRS, an experimental setup was developed. The field results obtained during February and March 2020 for two different configurations, showed that the double-glazing configuration in combination with ETICS has the potential to improve thermal comfort and reduce energy consumption. This paper addresses both the design of the SBRS and the obtained results from the experimental work. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thermal insulating mortars with lightweight aggregates replacing sand in different percentages are tested. • Thermal mortars are applied on brick substrate specimens and a prototype wall. • All mortars with insulating aggregates presented a thermal conductivity lower than 0.2 W/(m.K). • Mortars applied on the prototype wall showed enhanced mechanical properties than those applied on brick substrate specimens. The trend and the market of thermal mortars increased in recent years in both new and thermal retrofitting of building facades mostly due to their enhanced thermal performance. These mortars are formulated using different lightweight aggregates, thus allowing a significant reduction of both density and thermal conductivity. However, this latter aspect should not compromise either durability or mechanical performance. It is therefore of paramount importance to have reliable data on the performance of these innovative mortars, thus contributing to increase their efficiency and durability. The aim of this paper is to evaluate the thermophysical and mechanical performance of three commercially available and five experimentally designed lightweight thermal insulating mortars with several aggregates (expanded polystyrene, expanded cork, expanded clay, and silica aerogel) replacing sand in different percentages. These thermal mortars were studied on their fresh and hardened states and when applied on brick substrate specimens and a prototype wall, also evaluating the influence of the substrate on the performance of thermal mortars. Results show that lightweight thermal insulating mortars exhibited lower density, mechanical properties and thermal conductivity and higher capillary water absorption when compared to the control mortar (100 % sand aggregate). Moreover, mortars applied on the prototype wall showed enhanced mechanical properties and slightly higher thermal conductivity than those applied on brick substrate specimens. Nevertheless, all mortars with insulating aggregates (either applied on the brick substrate or prototype wall) presented a thermal conductivity lower than 0.2 W/(m.K), thus following the requirements of the EN 998-1 for thermal mortars. Results contribute towards the development of innovative and sustainable thermal insulating mortars with improved effectiveness and durability. [ABSTRACT FROM AUTHOR]

[Display omitted] • The new aerogel-based render presents a low thermal conductivity (0.029 W/m.°C). • The thermal conductivity of the aerogel-based render increases with moisture content. • The coating contributes to reducing the hygrothermal risk due to its low capillary absorption. • Hygrothermal risks of aerogel based-renders increase in colder climates. Silica-aerogel is one of the nanomaterials that contributes to increasing the thermal properties, due to its high porosity and low density, and also low thermal conductivity. The development of innovative thermal renderings is a current trend, but their impact on the hygrothermal performance of façade systems requires additional investigation. The main goal of the present work consists of discussing the hygrothermal performance of a new thermal aerogel-based render when applied as a component of a multilayer coating system. To achieve this objective, relevant hygrothermal properties were determined. An accurate analysis of the hygrothermal impact, considering different European climates, was also performed. A clear improvement of the thermal conductivity of the new render, at dry-state, (0.029 W/m.°C) was found. As the observed high open porosity (≈83%) leads to a high capillary absorption coefficient (0.129 kg/m2.s1/2), the prevention of moisture-related risks is a critical issue. Due to the high increase of the thermal conductivity (up to 400%), when saturated, the application of finishing materials is therefore decisive for the successful use of these renders in building envelopes. The numerical simulations highlighted significant hygrothermal risks at higher latitudes, observed by relevant temperature differences across the render thickness and significant external condensation potential. [ABSTRACT FROM AUTHOR]

• Assessment of water resistance, mould susceptibility and surface properties of ETICS. • Moisture content influence on the thermal conductivity of the insulation layer. • Definition of ETICS performance parameters. • Contribution towards the development of ETICS with improved durability. The use of External Thermal Insulation Composite Systems (ETICS) significantly increased in the last decades due to their enhanced thermal properties, low installation cost and ease of application, not only in new constructions but also for thermal retrofitting of building facades. These multilayer rendering systems are constantly exposed to weathering agents and anthropic factors which can lead to physical-mechanical and aesthetical anomalies and thus affect their durability. However, possible synergetic effects among these agents are often neglected by international technical documents on the evaluation of the effectiveness and durability of ETICS. With the aim of filling this gap, moisture transport properties (capillary water absorption, water vapor permeability, water absorption under low pressure, and drying kinetics), thermal conductivity, mould susceptibility and surface properties (color, gloss, and roughness) of twelve commercially available ETICS were assessed and discussed. Possible links between these factors were analyzed and ETICS performance parameters were defined. Results demonstrate that a deeper knowledge of the correlation among ETICS properties can effectively contribute to the evaluation of the efficiency and long-term durability of these systems. [ABSTRACT FROM AUTHOR]