Empirical and Numerical Analysis of an Opaque Ventilated Facade with Windows Openings under Mediterranean Climate Conditions

In recent years, there has been growing concern regarding energy efficiency in the building sector with energy requirements increasing worldwide and now responsible for about 40% of final energy consumption in Europe. Previous research has shown that ventilated façades help to reduce energy use when cooling buildings in hot and temperate climates. Of the different ventilated façade configurations reported in the literature, the configuration of ventilated façade with window rarely has been studied, and its 3D thermodynamic behavior is deserving of further analysis and modeling. This paper examines the thermal behavior of an opaque ventilated façade with a window, in experimentally and numerical terms and its impact in energy savings to get indoor comfort. Field measurements were conducted during the winter, spring and summer seasons of 2021 using outdoor full scale test cells located in Seville (southern Spain). The modeling of the ventilated façade was carried out using a three-dimensional approach taking into account the 3D behavior of the air flow in the air cavity due to the presence of the window. The validation and comparison process using experimental data showed that the proposed model provided good results from quantitative and qualitative point of view. The reduction of the heat flux was assessed by comparing the energy performance of a ventilated façade with that of an unventilated façade. Both experimental and numerical results showed that the ventilated façade provided a reduction in annual total energy consumption when compared to the unventilated façade, being compensated the winter energy penalization by the summer energy savings. This reduction is about 21% for the whole typical climatic year showing the ability of the opaque ventilated façade studied to reduce energy consumption to insure indoor comfort, making its suitable for use in retrofitting the energy-obsolete building stock built in Spain in the middle decades of the 20 century.

Development of a circularity assessment method for facade systems

Various authorities identify the circular building strategy as the best way to reduce the environmental impact of the building sector. The EURECA project aims to develop a circular facade system for the renovation of high-rise buildings. The circularity of the facade systems proposed within the project should be evaluated in an objective manner. Current circularity assessment methods exist, however, they appear unfit to evaluate facade systems at an early design stage. Based on the analysis of existing assessment methods a new circularity assessment method is developed. The developed method allows to measure the circularity on element level with a limited amount of required information, allowing early stage decision-making. The method considers the parameters recycling, environmental cost, expected service life, component dependency, layer dependency and flexibility for reuse. The method is tested on four facade renovation systems: standard ETICS, circular ETICS, ventilated facade with rigid insulation and ventilated facade with flexible insulation. The circularity of each system can be represented by a radar chart, giving the score per parameter, or by a single score. In addition to the circular aspect, the financial aspect is added in the evaluation of the facade systems by using the Pareto front method.

Fibre-Cement Panel Ventilated Façade Smart Control System

This paper outlines a design for a fibre-cement panel ventilated façade smart control system based on the acoustic emission method. The paper also provides methodology and test results, as well as statistical analysis of the three-point bending results with AE signal acquisition as a basis for the development of the system in question. The test items were samples cut from a full-size fibre-cement panel for interior and exterior use, according to the standard guidelines. The recorded acoustic emission signals were classified statistically into four classes, which were assigned to the processes occurring in the material structure as a result of the applied load. The system development was based on the differences between the characteristics of the individual signal classes and their number for each test case, as well as on the different distribution of successive classes over time. Given the results of the tests and the resulting conclusions indicating the applicability of the acoustic emission method (based on signal classification using the k-means algorithm for the assessment of variations in the mechanical parameters of cement-fibre composites), a methodology for such assessment was therefore developed. The approach proposed is a reasonable method for assessing the variation in mechanical parameters of fibre-cement panels on the basis of the parameters determined by the non-destructive method indicated.

Efficiency of ventilated facades in terms of airflow in the air gap

The gradual exploitation of the natural environment has forced most developed countries to promote ecological solutions and the development of sustainable construction. Ventilated facades perfectly match into this trend, and with their appropriate design, they bring real energy savings. This paper analyzes numerically the influence of the inflowing air, mimicking the wind, on the efficiency of heat removal from the ventilated space and heat transmission by thermal radiation and conduction through the consecutive layers of the external wall. For the purpose of comparison, two variants of ventilated facade were adopted: open and closed joints, at different wind speeds prevailing outside. The results obtained show that in windless weather, the ventilated facade with open joints shows higher heat removal efficiency and thus lower heat transmission to the building interior. At higher wind speeds of 5 m/s, the open-joint and closed-joint ventilated facades achieve similar heat transfer efficiency, and the prevailing temperature inside the building for the two technologies is almost identical. Subsequent increments of incoming wind on the building result in minimal differences in the heat transmission to the building interior, representing changes of about 0.1°C at increments of another 5 m/s of incoming wind. Conscious use of this facade technology, along with appropriate urban design of cities, can help reduce the energy needed to cool buildings during the summer period.

Optimal Solution for an Energy Efficient Construction of a Ventilated Façade Obtained by a Genetic Algorithm

To design a residential or commercial building with high energy performance that would be economical at the same time, an analysis was performed that relates these two aspects of the problem. The first aspect is focused on evaluation of the thermal performance of a multi-layered wall in order to achieve the lowest energy consumption for heating and cooling. The second aspect of the analysis covered the choice of materials (type, thickness and price) so that the building has the lowest possible construction costs, but the best achieved thermal comfort. The three types of external walls with the same structure were analyzed in this paper. The lowest and highest values of the layer thickness offered by the manufacturer were chosen and their dynamic characteristics for the heat transfer were calculated. The following step was to perform optimization of the objective function, which was defined by the unit price of the material per mass of the material, that is, the economical aspect was provided. The genetic algorithm method was used to obtain the optimal thickness of the external wall layers that provided the best dynamic characteristics for the heat transfer in the defined conditions.

Experimental procedure for studying the degradation and alteration of limestone slabs applied on exterior cladding

The studied limestone is a well known Portuguese natural stone that occurs in Valverde – Alcanede region, located in the Maciço Calcário Estremenho (centre of Portugal). This stone is used in several exterior and interior applications such as paving, cladding, masonry and decorations. Slabs made of the studied limestone were installed in ventilated facade with a “kerf” anchoring system in a building located in Valencia (Spain). After approximately five years, signs of degradation were detected on the facades through changes in color, cracks and fissures that caused instability and collapse on several slabs. Limestone slabs comprise irregular patterns due to rock cutting across stylolites. These features represent ideal paths for fluid circulation through the slab and can be identify as vulnerability zones for exterior applications. Experimental procedure included several laboratory analyses in order to study clays and the iron oxide contents. Microscopic petrography, XRD and SEM observations were important to identify the interaction of the clay material in stylolites and fossil contours. Results show the importance of establishing standard methods for selecting stone on cladding applications. From the results, it is possible to understand that clay minerals have a strong influence on the mechanical performance of this stone. Among other important remarks, results show the importance of the development of standard procedures that acknowledge the structure and mineral composition before setting these natural products as construction materials. Proper stone selection was found important to avoid facade degradation, and hence contribute to prevent accidents and promote user safety as well as economic impacts.

Reduction of Load Capacity of Fiber Cement Board Facade Cladding under the Influence of Fire

The paper analyzes the issue of the reduction of load capacity in fiber cement board during a fire. Fiber cement boards were put under the influence of fire by using a large-scale facade model. Such a model is a reliable source of knowledge about the behavior of facade cladding and the way fire spreads. One technical solution for external walls—a ventilated facade—is gaining popularity and is used more and more often. However, the problem of the destruction during a fire of a range of different materials used in external facade cladding is insufficiently recognized. For this study, the authors used fiber cement boards as the facade cladding. Fiber cement boards are fiber-reinforced composite materials, mainly used for facade cladding, but also used as roof cladding, drywall, drywall ceiling and floorboards. This paper analyzes the effect of fire temperatures on facade cladding using a large-scale facade model. Samples were taken from external facade cladding materials that were mounted on the model at specific locations above the combustion chamber. Subsequently, three-point bending flexural tests were performed and the effects of temperature and the integrals of temperature and time functions on the samples were evaluated. The three-point bending flexural test was chosen because it is a universal method for assessing fiber cement boards, cited in Standard EN 12467. It also allows easy reference to results in other literature.