Keywords

1 Introduction

For several years, the construction sector has been called upon to respond to the pressing demand for new energy and environmental qualities, partly because of the acceleration of climate change effects (IPCC 2021). Supporting this scenario, the Global Status Report 2020 for Buildings and Construction, published by the Global Alliance for Buildings and Construction (GlobalABC), notes that the construction sector's share of global energy-related CO2 emissions rises to 38% (United Nations Environment Programme 2020). Therefore, EU actions and policies will have to contribute to the objectives of the European Green Deal and the Paris Agreement, promoting strategic planning on energy efficiency and climate (Commissione Europea 2019).

Researchers and various players in the construction industry, including companies, businesses, and different stakeholders, want to provide concrete answers to building safer and more efficient environments.

This approach promotes the integration of high-performance components and highly innovative products that facilitate the monitoring and management of environmental and energy performance at the building scale.

Against this, there are new experiments aimed at demonstrating the possibility of equipping buildings with systems that offer “dynamism” useful for the management of flows, like a living organism (Milardi 2016). The complex evolution of the envelope is moving toward its evolved functionalization. The envelope is a three-dimensional closure system composed of several interdependent elements called upon to regulate performance related to the passage of energy and environmental flows.

Therefore, the envelope specializes in the deployment of new control and performance response systems through the interaction between the external world and the internal environmental elements; the maintenance of conditions of well-being and comfort depends on this relationship.

At the same time, it is increasingly evident that climate change requires a substantial modification of building design approaches to make urban systems more adaptive to climate change. In particular, buildings are exposed to increased risks of damage from the expected impacts of climate change, including more frequent high winds, increased heat, particularly in cities (Urban Heat Island effect), floods, and fires that accompany some extreme weather events.

In recent years, climatic conditions in Mediterranean areas have been characterized by rising temperatures, water bombs, and increasingly frequent micro-typhoons known as Medcane (cyclones formed in the Mediterranean) (Mejorin et al. 2018), becoming the new requirements in terms of quality that building envelopes must meet. As multiple factors change, such as the performance conditions of building envelopes and climatic conditions, there is a need for measurable control, at the basis of the “building-context relationship,” through new modes of investigation to measure the effects of extreme events on buildings and, where possible, verify the outcomes of their bi-univocal relationship.

The contribution presented here is part of this context and concerns experimental research to verify the performance characteristics of building envelopes in a specific environmental context, developing laboratory experiments, according to standard protocols (UNI/EN, ASTM, AAMA) on a type of transparent façade.

Most of today's curtain wall systems are technologically improved and satisfy higher requirements. However, recent studies indicate that test results from specialized laboratories show that the continuous impact of environmental conditions causes a significant loss of performance (up to 54% due to air infiltration, 18.53% due to wind pressure) over the life of the curtain wall system (Ilter et al. 2015). Mandatory façade performance tests such as air permeability, water impermeability, and wind resistance applied to full-scale curtain wall models can help obtain preliminary information on system performance before the installation process. However, passing these tests does not guarantee that the system's performance in terms of durability will match the test results (Yalaz et al. 2018). Specifically, the case study analyzed is a portion of a curved transparent façade, on a 1:1 scale, made available for experimental research activities by TCLab partner companies, GLASBILT LLC.Footnote 1

The experimentation activities took place at the TCLab SectionFootnote 2 of the Advanced Testing laboratory facility, the Building Future Lab of the Mediterranean University of Reggio Calabria. The laboratory makes it possible to test new approaches and technical systems to control the overall quality of the building and its urban context. Using the instrumentation and machinery available in the TCLab Section, which reproduces extreme climatic stresses on mock-ups of envelopes, it is possible to study the envelope's performance and measure their resilience characteristics.

2 Methodology and Instruments

The approach for the experimental activities lies in the current and fertile scenario of climate change studies in the urban environment. It is an emblematic example of the intellectual and operational challenge posed by today's human fields of action, where technological innovation and experimentation are possible tools for understanding their behavior. Based on current needs, urban growth, and climate change, the development of energy-efficient buildings may become particularly critical for the future (Merlier et al. 2019).

The general objective of the studies is to identify some critical nodes between buildings and their contexts and assess the stresses of climatic phenomena affecting the building envelopes, recalling the need to verify the technical feasibility of interventions, oriented and supported by experimentation, and validation of the results obtained.

From a methodological point of view, the first part of the research study consists of understanding the evolving climate change scenario in the Mediterranean area (Sannino et al. 2016) due to islands and heatwaves, high-intensity rainfall phenomena such as water bombs, and micro-typhoons. These phenomena can cause direct damage to the envelope of buildings, with particular attention to their façades and the identification of building elements to be reinforced to avoid severe damage to affected properties and the safety of people. The aim is to prevent the “cascading effects,” where one defective piece causes other pieces to fail, leading to disproportionate consequences. Studies and regulations prescribe that curtain walls must be air and watertight, prevent the formation of condensation on internal surfaces, and resist wind load and other external forces acting on the building envelope. Therefore, assessment is essential to minimize the risk of undesirable and costly problems during a building's expected lifetime (Gonįalves et al. 2010).

Subsequently, the boundary conditions between the building and its context are recreated in the laboratory to initiate experimentation and identify the behavior of the curved façade in situations of extreme climatic events, in particular heatwaves and rain floods. In this phase, the focus shifts to the performance of the curved façade, with the final objective of developing test protocols, both for subsequent experimental activities and certification in the regulatory framework.

The instrumental research opportunity for the study of environmental phenomena involving the building envelope is provided mainly by two large pieces of equipment in the laboratory: a “test chamber” (Test Lab) and a climatic simulation “Cell” for accelerated indoor and outdoor tests (Test Cell).

Specifically, the Test LAB is a “test chamber” built according to the operational characteristics of the test set. It consists of a steel-framed structure measuring 18 (15 effective) × 12 × 2.50 m, where mock-ups of curtain walls (according to UNI definition), windows, and doors (or similar elements) are mounted on a scale of 1:1 and tested according to unified protocols.

The Test Cell is a structure for the thermodynamic characterization of full-scale building envelope systems, usable in a closed or open environment. It consists of three independent units installed on a support platform and managed by a control PC. It calculates the thermal performance of buildings, as indicated by the UNI/TS 11300-1 standard, and is fundamental for the regulatory verification and testing of vertical and horizontal closure components, roofs, doors, windows, etc.

The complex operation of data collection, processing, and systematization led to the drawing up of test reports of the comparison and verification of the experimentation carried out. The following section describes the experimentation activities.

3 Experimental Procedure

Field experimentation is commonly interpreted as the study of the behavior of buildings—stressed by the reproduction of climate change phenomena—through experimental activities and tests on full-scale models, called mock-ups.

In this case, the mock-up under examination is a curved curtain wall consisting of an aluminum mullion and transom frame and three openings (one window and two doors), including a balcony, which is not considered for the overall performance of the façade system (Figs. 63.1 and 63.2).

Fig. 63.1
Two illustrations of a glass frame of a building along with its dimensions. It has 6 frames with 3 openings. The first, the fourth short frame, and the fifth frames are opened.

PMU—project mock-up of curved façade, elevation, and sections (Credit Glasbilt)

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Fig. 63.2
An illustration of a glass frame with a curved end along with its measurements. A line from the top left bends and goes concavely upwards.

PMU—project mock-up of curved façade, plan (Credit Glasbilt)

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The experimental phase starts with the identification of the urban layout to be simulated in the laboratory: It is assimilated into a building with an external space similar to a courtyard. The test chamber (dimensions 17 × 12 × 4.50 m) is closed on three sides; on the fourth external side, the curved portion of the façade is located, allowing direct interaction with the external climatic conditions and offering the possibility of modeling them to specific requirements. In addition, the test chamber is equipped with three seismic beams for performing displacement and elastic equilibrium tests. Other machines are a big fan that simulates winds of up to 200 km/h, a thermal chamber (dimensions 7 × 5 × 1.50 m), and an internationally patented retractable rain simulator (Trombetta and Milardi 2015).

About the phenomena to be analyzed, the following procedure is identified for the experimentation activities:

  • Heatwave: The experimentation is carried out by reproducing a wind flow through the AAMA/ASTM fan—simulating the power of a hurricane—to verify the performance behavior of the mock-up's curved external façade subjected to strong pressures;

  • Pluvial flooding: The experiment is conducted by reproducing a constant rainfall directly on the mock-up's outer façade. Three simulations of the water jet through a network of sprinklers with calibrated nozzles are carried out: in the absence of wind, in the presence of wind, and under extreme wind conditions (hurricane power).

The objective of the tests is to assess in the laboratory the opening/closing performance, preload, air permeability, water tightness under static pressure, water tightness under dynamic conditions, and structural performance.

For this type of façade, the following test methods are planned and performed:

  • Air Leakage Resistance Test (ASTM E283): applying a (negative and positive) pressure differential of 6.24 psf/300 Pa, after determining the loss of the system (Fig. 63.3);

  • Water Penetration Resistance Test (ASTM E331): applying a static pressure differential of 10 psf, 480 Pa for a period of 15 min with five gallons of water per square foot per hour (= 3.4 l/min m2), with a watering device consisting of a square-meshed network of nozzles positioned on a horizontal plane parallel to the plane of the specimen (Fig. 63.4);

  • Dynamic Water Resistance Test (AAMA 501.1): applying a dynamic pressure differential of 10 psf for a period of 15 min with five gallons of water per square foot per hour (= 3.4 l/min m2), with a watering device consisting of a square-meshed network of nozzles positioned on a horizontal plane parallel to the plane of the specimen;

  • Uniform Load Deflection Test (ASTM E 330): applying a positive and negative test pressure equal to 50% and 100% of the design wind load, for which measurements and checks are carried out to verify that, under these effects, the mock-up presents an admissible deformation and retains its stability characteristics.

Fig. 63.3
A photograph of the first floor of a building with a transparent glass wall. Rod frames are installed on the outer side of the glass wall.

Air permeability test (Credit: TCLab)

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Fig. 63.4
A photograph presents the side view of a building with a transparent glass wall. Rod frames that are connected to tubes are installed on the outer side of the glass wall.

Watertightness under static pressure (Credit: TCLab)

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From the experiments carried out, a framework for reading and comparing performance data is constructed to highlight the potential, criticalities, and malfunctions of the technological systems that characterize the typological and geometric layout of the mock-up analyzed.

From the experiments carried out, a framework for reading and comparing performance data is constructed to highlight the potential, criticalities, and malfunctions of the technological systems that characterize the typological and geometric layout of the mock-up analyzed.

4 Results

The data analyzed do not show negative behavior of the curved façade, for the simulation of the heat island and pluvial flooding in the absence of wind, obtaining a positive and flexible reaction behavior of the system. The performance verification under conditions of pluvial flooding with wind reveals water infiltration, thus requiring attention in the production, installation, and installation of rainwater drainage systems for this type of façade. In extreme wind conditions, on the other hand, the mock-up reacts because the pressure generated by the fan disperses the flow of water on the façade; thus, no water accumulates and avoids infiltration inside the building envelope.

As shown in Table 63.1, the air infiltration test is passed: for fixed windows 0.1 CFM and for opening windows 0.30 CFM.

Table 63.1 Results of air infiltration test
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The optimum results of the structural test are conducted at a negative pressure of 1676 Pa and a positive pressure of 3064 Pa through the use of specific sensors that read the displacements of the façade at particular points (Fig. 63.5). Table 63.2 shows the data of the test performed.

Fig. 63.5
An illustration of a glass frame with 6 columns along with its measurements. Three sensors labeled A, B, and C are installed in the frame. C at the first, B at the second, and A at the fifth column.

Sensors position inside the chamber (Drawing by TCLab)

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Table 63.2 Results of structural performance
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Table 63.3 shows the absolute deformation values for comparison between opening and fixed elements.

Table 63.3 Deformation values
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From the tests carried out, the results materialized in experimentation protocols that represented a real added value to the research, realizing applied experimentation actions with highly reliable results.

5 Conclusion

The research focused its efforts on the assumption that curtain walls guarantee constant performance thresholds calibrated to the average values required by the standard, resulting in envelopes that perform the same even under different contextual conditions.

The results and evaluations of this experimental research on a full-scale mullion and transom curtain wall mock-up, even if the system passed the performance tests, show how deficiencies or failures can occur during their service life, especially in the face of sudden climate changes. From this point of view, the testing process is understood as an adaptive control tool for climate change, based on measurements and performance assessments against specific environmental reference contexts. That is, the more traditional aspect of modeling and simulation has to be extended, with testing protocols requiring new methodological approaches and infrastructures capable of responding innovatively to market trends and stringent industry regulations (Milardi 2021).

Although the main objectives of the experiment are achieved, it can be considered a work in progress, as it opens up promising fields of investigation. It would be interesting to record the dynamic trend of the thermal values on the mock-up, either with a thermometer or a thermal imaging camera at regular intervals to verify the heat propagation.