Search

This paper aims to study various spatial functional layouts and test how these different design approaches affect pedestrian comfort under shell structures. The considered shell shape was developed aiming an efficient distribution of loads allowing prefabrication with ultra-thin concrete elements. As shell structures can define semi-exterior spaces and assume open locations within some urban contexts, the study of how different design strategies for the underlying space affect user's comfort is of upmost importance. Several wind tunnel tests were performed on a triangular thin shell scale model with a few different spatial user's area layouts allowing to understand to which extent some design decisions compromise pedestrian wind comfort. The experimental campaign follows an iterative process leading to conclusions that can guide future projects and contribute to a multidisciplinary and transversal understanding of these innovative structures. • Wind tunnel tests for pedestrian comfort assessment under free form concrete shells. • Study of pedestrian comfort's influence on space occupation for semi-exterior spaces. • Integrated design solutions for functional and comfort needs. • Most critical areas under the shell's legs, depending greatly on each design solution and wind incidence. [ABSTRACT FROM AUTHOR]

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]

One of the most important concerns when designing buildings as liveable spaces is the indoor comfort. This depends on different factors, including daylight availability and discomfort glare conditions. The increasing use of glazing areas in the building's envelopes can lead to high energy consumption and problems such as visual discomfort. The use of shading devices stands out as a sustainable design strategy to reduce energy consumption in the buildings. This work presents an experimental analysis of the impact of an innovative shading device, a double-tilted venetian blind (DTVB) with different positions of upper and lower slats, on the indoor daylight conditions. Moreover, discomfort glare evaluation, through DGPs metric, is performed. The experimental campaign was conducted in an outdoor test cell during three periods of the year: summer solstice, winter solstice and autumn equinox. Experiments were carried out with both white and grey DTVBs, for several positions of upper and lower slats, under clear and overcast sky conditions. This comprises the measurement of indoor and outdoor horizontal and vertical illuminances and irradiances and solar and visible transmittance of the fenestration. It was concluded that DTVBs can achieve a higher performance, regarding solar protection, daylighting and glare control, when compared with more traditional venetian blinds systems. • Experimental daylight performance study of an innovative shading device. • A double tilted venetian blind (DTVB) with different slats angles was studied. • Daylighting parameters were measured in a test cell. • White and grey DTVB slats were evaluated under clear and overcast sky conditions. • DTVB have higher daylight efficiency than traditional Venetian blinds. [ABSTRACT FROM AUTHOR]

An accurate assessment of the airflow in naturally ventilated double skin facades (DSF) is crucial for a correct design and performance evaluation. Measuring and predicting DSF airflow is not a straightforward task, given the stochastic nature of the wind, which can assist or oppose the buoyancy force. The present paper resumes the results of airflow measurements inside a naturally ventilated double skin facade using a tracer gas technique. The tests were performed on an outdoor air curtain (OAC) DSF test cell with a movable slat venetian blind. Measurements with no active shading and at night were also performed. Outdoor and test cell air gap temperatures were continuously measured and wind pressure coefficients were determined from wind tunnel tests. Experimental results were then compared to those obtained by a simple model taking into account both thermal and wind effects on the facade. From this comparison discharge coefficients were estimated, which can be used for characterizing the DSF behaviour. [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]

Abstract: The increasing use of glazed areas in the building envelope can lead to high solar gains and glare problems that can strongly impact the entire building energy consumption, peak loads and indoor comfort. An important and fundamental strategy in sustainable building design for controlling solar heat gains and daylighting through fenestration is the use of shading devices. Therefore, it is recommended to use detailed models that can accurately estimate the optical properties of the different types of shading devices (such as roller blinds and venetian blinds) and include their effects in the glazing system analysis. This paper describes a net radiation method for determining both solar and visible optical properties of glazing with shading devices, particularly venetian blinds. Some numerical results were compared with in situ experimental measurements carried out in an outdoor test cell. The experimental work included the measurement of illuminance and irradiance fluxes and the determination of the visible and solar transmission properties of the fenestration system. The agreement between numerical predictions and experimental results was better for overcast than clear sky conditions. Moreover, a venetian blind control strategy that blocks direct solar radiation, whilst enabling the transmission of diffuse radiation to indoors, is implemented. [Copyright &y& Elsevier]

• 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]

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 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]

• 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]