Exploiting the Value of Active and Multifunctional Façade Technology through the IoT and AI

Abstract

In recent years, the interest in multifunctional façade (MF) technology has increased significantly. Recent advances in the integration of active and passive technologies have led to a new concept of building skins with highly flexible and decentralized control. Such an approach is considered capable of tackling environmental challenges and enhancing indoor environmental quality (IEQ). Integrated HVAC systems, dynamic blinds, and renewable energy systems can drastically increase façade responsiveness and efficiency. Although the technical feasibility of active and MF technology has already been demonstrated, market applications are still limited. The goal of this paper is to define the state of the art of MFs and clarify how the integration of IoT technologies, supported by AI, can increase market interest by fully exploiting the value of these systems. Indeed, recent advances in the IoT and data analysis tools are opening up attractive scenarios in optimization process. Starting with an overview of the most interesting EU-funded projects, this paper presents a MF case study in which IoT infrastructures are fully integrated. The prototype, realized within the MEZeroE Horizon project, stimulates a debate on future trajectories (and gaps) for the marketability of MF.

1. Introduction

The building sector is facing a period of deep transformation. On the one hand, it must adhere to the European Union’s policies for decarbonization of the built environment [1,2]. On the other hand, it must meet an increasing demand for high standards in indoor environmental quality (IEQ) to ensure the user’s well-being and a healthier environment [3,4]. To face both challenges, the EU has pinpointed the building façade sector as a perfect incubator for exploring transformative innovation for the entire construction domain [5,6]. Indeed, the building façade plays a critical role in impacting a building’s overall energy consumption [7] and carbon footprint [8], and simultaneously, it is strictly responsible for the IEQ and users’ well-being [9,10] by impacting thermal, acoustic, and visual comfort. Thus, several research projects have been funded by the EU for the years with the aim to develop innovative and high-performance building skins [5,11].

In this context, one of the most interesting scenarios in balancing energy efficiency aspects and IEQ refers to the development of active and multifunctional façade (MF) systems [12]. Compared to a “traditional” building skin, a MF expands the façade’s role by incorporating additional functionalities and enhancing performance, including aspects of modularity and prefabrication [13]. Various systems such as heating, ventilation, air conditioning (HVAC), automated blinds, solar panels, and photovoltaics technologies can be integrated into the building envelope to optimize energy efficiency, exploit renewable energy, enhance thermal insulation, improve indoor air quality, and assure high and responsive IEQ [14]. By transforming façades into active and adaptive building components, the system’s ability to meet environmental and user comfort needs increases significantly. In this perspective, the MF system can adjust the visual, thermal, and acoustic performance of a building according to environmental conditions or specific users’ needs.

However, despite the significant technical advances in conceptualizing, designing, and prototyping complex MF systems, widespread adoption in the market is still limited [15,16,17]. Although the construction market is characterized by a certain latency in integrating innovative technologies and systems, some issues need to be addressed before MF is a ready-to-market technology. Aspects related to cost, the supply chain, design complexity, long-term benefits, system integration, and MF control are identified as the main obstacles that limit product scalability in the market [16,17,18]. This paper, starting by defining the state of the art of MF systems, aims to clarify how the Internet of Things (IoT) and Artificial Intelligence (AI) technologies can be integrated to address technical barriers and, consequently, foster market deployment. Indeed, recent advances in the field of IoT technologies and AI for the built environment are enabling a new situation-aware paradigm for decision making [19] needed to achieve higher levels of efficiency. The potential contribution of digital innovation is also recognized by the European Commission as a key strategy for enabling sustainable models and promoting the more rational use of resources [20]. In this paper, these benefits are assumed as potential innovative factors to exploit the value of MF systems. Although several theoretical studies have investigated topics of the façade sector [12,21,22], few real experiences have been carried out. This implies a gap in the research on the topic. As reported by Founti et al. [11], further research in recognizing the added value of advanced façades provided by digital technologies is needed to address significant market segments. In this perspective, the development of prototypes is a key action to investigate the advantages and obstacles to be addressed to trigger the technology transfer from research to industry [23].

The novelty of the paper lies in a real case study used to address technical, managerial, and economic issues. This approach is essential to grounding the research efforts and results. This paper is organized as follows: After a methodology section, this paper provides an overview of MF technology, starting from an assessment of European case studies. Subsequently, the MEZeroE MF prototype is presented as the result of an open innovation approach, and finally, the discussion and conclusion parts summarize the main achievements reached and future perspectives on the topic.

2. Materials and Methods

This research is conducted within the framework of the MEZeroE Horizon 2020 project (GA ID 953157). This EU-funded initiative aims to establish a collaborative ecosystem to promote product and process innovation in the building façade sector for the development of highly energy-efficient and healthy nearly Zero Energy Buildings (nZEBs). Embracing an open innovation approach [24], the specific goal of the MEZeroE project is to support the development of innovative high-performance building envelopes through the sharing of knowledge and the creation of a Living Lab and test facilities for cutting-edge solutions [25].

Through a real case study, this paper investigates the potential role of the IoT and AI integrated in a MF as enabling factors to facilitate product marketability. Before presenting the technical features of the innovative building skin, a wider overview of the topic is provided to contextualize the research activities in a theoretical and technological framework. Specifically, a list of relevant MF case studies is collected through the CORDIS database on EU-funded projects [26], white papers, and open-access research papers. This activity is needed to clarify the state of the art and investigate the reasons for a lack of market penetration years after the first prototypes. A qualitative assessment of the results is carried out to confirm (or refute) aspects already described in the literature and investigate how digital technologies can now be integrated for value exploitation and marketability. This paper focuses mainly on aspects of digital/physical integration, digital technologies, and façade control algorithms as the most novel part of the research. Integrated technologies such as heat pumps, mechanical ventilation, automatic blinds, and opening windows are, in fact, products already on the market. The MF prototype, reaching a TLR of 7, has been tested in an operating environment.

3. The Multifunctional Façade Concept

There is no unambiguous definition of the MF. Despite years of investigation, the “multifunctional” term refers to a wide range of functionality and, consequently, technologies that are difficult to fit into closed classifications. For this study, the term MF refers to a fully prefabricated modular building envelope that includes passive and active components to provide a set of non-traditional and customizable functions (Figure 1) [13]. Passive components are generally no-energy-using technologies to assure basic functions, and active components represent additional sub-systems powered by energy for improving or expanding façade functionality. On the one hand, passive components refer to insulation panels, internal or external solar shadings, and other technologies needed to ensure the main envelope functionality, such as mechanical behavior, thermal resistance, air and water tightness, and noise reduction.

On the other hand, a wide range of technologies can be considered active components, able to improve façade performances or provide new customized services such as mechanical ventilation or renewable energy systems (RES) [16,27].

In this context, several EU-funded projects have been developed in the last fifteen years to test and validate the technical feasibility of MF systems [5,11], as they are considered impactful technologies for starting deep renovation schemes of the existing building stock [28]. Indeed, most of the EU-funded projects presented in

Table 1. EU-funded projects on multifunctional façades.

EU Project	Project Year	MF Technology Description	TLR	Website Ref.
Meefs	2012–2016	Meefs develops two new energy-efficient modules for retrofitting including PV panels, solar thermal units, and a green façade module.	TLR 9	[29]
Adaptiwall	2013–2017	Adaptive wall is a novel panel consisting of 3 elements: lightweight concrete with nano additives; adaptable polymer for switchable thermal resistance; and a total heat exchanger with nanostructured membrane.	TLR9	[30]
Plug-N-Harvest	2017–2022	Plug-N-Harvest develops a plug-and-play module for building retrofit including a PV module, battery, thermal collector, electric heat, and automatic ventilation.	TLR5	[31]
Energy Matching	2017–2022	Energy Matching develops a BIPV module with high aesthetical value and flexibility.	TLR9	[32]
RenoZEB	2017–2022	RenoZEB will provide a cost-effective plug-and-play façade integrating ventilation systems, solar and PV, automated blinds, and sensors.	TLR9	[33]
PowerSkin Plus	2019–2024	PowerSkin Plus combines enhanced insulation and renewable energy technology based on photovoltaics in modular solutions.	TLR8	[34]
ENsnare	2021–2025	The ENSNARE project will strive to increase the implementation of renovation through digitalization. A MF with BIPV, PV, a roll-bond solar collector, thermal batteries, and windows will be developed.	n.a.	[35]
MEZeroE	2021–2026	MEZeroE will focus on developing nZEBs. A MF is developed integrating mechanical ventilation, heating and cooling systems, automated blinds, and window sensors.	TLR8	[25]

aim to develop a fully prefabricated façade for building retrofits.

From a qualitative assessment of these projects, some considerations can be made. According to the type of technology to be integrated, different types of Technology Readiness Levels (TRLs) have been reached, and different market adoptions have occurred.

Firstly, as demonstrated by Meefs and Energy Matching projects, the integration of RES, including solar and PV modules, has been viable for the construction market for several years [5]. Concerning RES technologies, obstacles to the widespread adoption of MF systems still relate to architectural, aesthetic, and energy efficiency issues. In this context, an intriguing perspective, as explored in the Plug-N-Harvest case, involves incorporating batteries for energy harvesting to transform the façade into active nodes of smart microgrids [36]. Although this perspective is very attractive, the lack of a multi-scalar infrastructure (from the building to the city) limits its application. In addition to this, the integration of advanced materials has gained much interest among researchers. In the AdaptiWall project, phase-change nanomaterials were integrated to enhance energy performance and control temperature, moisture, and indoor health. The integration of such advanced materials is still hampered by higher costs with respect to traditional materials and a lack of knowledge by designers, as well as a lack of communication across the entire supply chain [37].

Again, several EU projects are exploring the benefits of “plug & play” façades capable of integrating HVAC systems. Such an approach holds significant promise for technologically upgrading the existing building stock, which must meet escalating comfort and efficiency demands [38]. Within the framework of RenoZEB and MEZeroE projects, a MF with integrated heating, cooling, and ventilation system technology has been investigated and developed [25,33,39]. If, on the one hand, these projects have shown how technical issues can be managed for real applications [11], on the other, it is evident how far the commercialization of such products has come. Indeed, achieving a fully integrated MF product means redesigning both technologies and the entire supply chain.

All these experiences have demonstrated that MF technology represents a niche of the façade industry. Indeed, despite ongoing efforts toward developing fully integrated systems, practical application experiences remain limited to prototypes and case study demonstrations [11]. As highlighted in the white paper [17], there still is no market for the widespread deployment of active multifunctional systems, as clients and designers do not recognize their value. This implies that the benefits of MF systems in terms of energy savings and comfort provided need to be demonstrated to attract greater market interest.

In the proposed projects, the focus on sensor integration mainly involves monitoring the performance of integrated technologies. Only in RenoZEB and MEZeroE is strict reference made to the use of such sensors for the regulation of active systems. From this perspective, the use of IoT sensors in combination with AI algorithmic control systems remains an open issue with great room for improvement. Although the topic is relevant in the research landscape for building energy optimization and IEQ, this topic has not yet been analyzed in relation to complex envelope systems.

4. An IoT-Based Multifunction Façade Prototype

The MEZeroE MF is a complex advanced system designed to offer a highly adaptive building skin for users’ multidomain comfort and to enable energy efficiency actions. Different experts have been involved during the design and manufacturing phase to aid in the development of a non-standard product. This complexity comes from the integration of active and passive technologies put in communication with each other through an IoT infrastructure. Through these technologies, this façade can shift to several configurations based on internal and external environmental stresses and user feedback. This flexibility allows for greater adaptability to changing conditions throughout the day, week, and season. The opening of windows, adjustments to blinds, and control of the heat pump and mechanical ventilation are thus managed through a physical (and digital) intelligence installed in the façade. To investigate the behavior of the façade, a prototype of dimensions 3750 × 3000 mm was designed (Figure 2), built, and tested (Figure 3). The prototype has been prefabricated in a factory.

Precisely, the prototype comprises two unitized curtain wall façade modules with vision and spandrel panels to replicate the real conditions in a building. Specifically, the façade system technology is a close cavity façade (CCF) with structural sealant glazing of the glasses to the aluminum profiles. The CCF system exploits the cavity generated between two layers (approximately 53 mm) to increase the thermal performance of the system. Externally, a low iron heat straightening glass (55.2) with anticondensation coating is used to limit the radiative exchange between the sky and the glass. Internally, the vision panel consists of triple glazing (4-18-4-18-44.2) with argon (90%) and a double low-e coating in face #3 and #5. The spandrel panel is composed of the same external glass, and a metal sheet is installed behind the outer layer to ensure façade uniformity from the outside and cover the technical space and insulation layer. From a thermal point of view, this system has the following performance:

• Thermal transmittance: U = 0.5 W/m²K;
• Solar factor (no blind): g = 0.45;
• Solar factor (with blind): g = 0.04;
• Solar transmission (no blind): Tl = 0.64.

In the MEZeroE MF, the following components are integrated (Figure 4).

4.1. Dynamic Blinds

Solar radiation is regulated by roller blinds installed in the CCF. An adjustable lamella with a high degree of reflection is designed to regulate the thermal load inside the building, reducing the load on summer days and exploiting it on winter days. The lamella system allows for double adjustment: firstly, the blind can be raised and lowered, and secondly, the slat can be oriented to 180°. This allows for a high degree of flexibility in proving shade from sun’s rays according to the position of the sun, while at the same time ensuring maximum visual and perceptual comfort. The engine of the lamella and electrical and data cabling have been integrated into the façade frames to guarantee the best architectural integration. For the MEZeroE MF, an on-board control unit for dynamic blinds allows the operation to proceed according to a schedule. The lamella control unit is managed via a KNX signal.

4.2. Automatic Window

The vision façade module is an opening window with an automatic overhang system. The window opening can be adjusted in percentage, and it allows for the possibility of exploiting free heating and free cooling for energy saving or the exchange of indoor air if CO₂ levels are higher than the threshold. The window engine is integrated in the façade frame using a commercial product that allows for a total integration into the façade. The opening is controlled via a KNX signal.

4.3. Heat Pumps and Mechanical Ventilation

A heat pump and mechanical ventilation system were integrated into the prototype to provide a fully autonomous system. A commercial product for nZEB installation has been selected and integrated directly into the façade. This was selected from the market according to several parameters such as cooling/heating power, cost, and the possibility of not installing an external machine. The development of a fully customized solution was not considered, as this would require a long development time. Specifically, a thermodynamic controlled mechanical ventilation is selected to ensure double flow, heating, and cooling dehumidification. Although the physical integration will have to be rethought according to the building type (e.g., the presence of the ceiling, slab), the prototype allows for an evaluation of the potential benefits of a decentralized system with a good degree of approximation. In the MEZeroE MF, the HVAC system takes and ejects air directly from the hidden holes provided in the perimeter of the spandrel frame. Specifically, one of the two modules is responsible for air intake, the other for extraction. From an aesthetic point of view, this solution means that there are no visible air vents in the façade or external units. A smart thermostat is generally used to control and set the indoor air temperature, but for the MEZeroE prototype, the smart thermostat is replaced with a dedicated IoT infrastructure with edge-AI. Data gathered from IoT sensors are communicated to an on-board PCB (printed circuit board) to manage the adjustment of the different machine components (e.g., air velocity, air temperature, etc.). In this case, data are communicated in the Modbus protocol.

4.4. IoT Sensors for Façade

Several sensors are integrated in the building façade to monitor environmental parameters and regulate technologies automatically. Specifically, the IoT system is a proprietary kit [40] composed of three sensor nodes designed for a curtain wall façade for a full integration with an edge-AI to trig data transmission and optimize data collection. The kit is currently energy supplied by wire, and it communicates data collected via LoRaWan to a Modberry gateway. The LoraWan protocol was adopted due to a low energy consumption need and the low data rate for monitoring environmental trends. As a Modbus IoT kit system, as reported in Figure 5, IoT kit nodes are called Master, Slave 1, and Slave 2: the “Master” node is integrated in the lower transom of the vision part (not openable), and it monitors the transom temperature, glass temperature, and internal radiation passed through glass; the “Slave 1” node is integrated in the mullion at 140 cm from the interior floor and monitors indoor parameters and mullion temperature; the “Slave 2” node is installed into the mullion within the vertical and monitors outdoor parameters. The kit was designed to match sensor requirements for dimension, range, precision, and cost so to have a cost-effective, low-cost, and aesthetically appealing solution in line with curtain wall façade market expectations. Bespoke PCB have been designed, manufactured, and integrated within a 3D powder-bed fusion case. The selection of these sensors was established to support the data collection, analysis, and utilization of parameters to enable users’ multidomain comfort and energy efficiency. The list of sensors integrated in the kits is shown in

Table 2. List of sensors integrated in MEZeroE MF.

Sensor Kit	Parameter	Units	Range Value
Master (transom)	Glass surface temperature	°C	−40 to 200 °C
	Transom surface temperature	°C	−10 to 50 °C
	Internal solar radiation	W/m2	0 to 1500 W/m2
Slave 1 (internal mullion)	Internal air temperature	°C	−55 to 125 °C
	Internal relative humidity	%	0 to 100%
	Internal illuminance	lux	0 to 100 klux
	Internal CO2	ppm	0 to 1000 ppm
	Internal TVOC 1	µg/m3	0 to 110 kPa
	PIR (presence)	-	0/1
Slave 2 (external mullion)	External air temperature	°C	−55 to 125 °C
	External relative humidity	%	0 to 100%
	External pressure	Pa	0 to 110 kPa
	External illuminance	lux	0 to 100 klux
	External solar radiation	W/m2	0 to 1500 W/m2
	External noise	dB	0 to 130 dB

¹ TVOC: total volatile organic compounds.

.

4.5. Façade Control System

The MF MEZeroE multifunctional façade is managed through a Modberry gateway that collects and analyzes sensors every 5 s and uses ruled-based decision-making AI to define input for the integrated technologies. Thus, environmental data feed energy and IEQ algorithms for adjusting actuation for the heat pump, mechanical ventilation, solar blinds, and opening of windows. These optimization rules also included aspects related to acoustic, perceptual, visual, and air quality to provide multidomain comfort for users. The rules are managed and implemented in Node-RED, an open-source flow-based development tool designed for visual programming. It offers a user-friendly interface for connecting hardware devices, APIs, and online services to IoT sensors, automation workflows, and more.

The main rules for energy and IEQ optimization can be summarized as follows (in order of prioritization of the algorithm functionality):

• Energy and thermal comfort. Depending on the season, different temperature thresholds are set to ensure ideal thermal comfort. These rules provide operating ranges according to the predictive mean vote (PMV) and predicted percentage of dissatisfied (PPD) standards defined for office buildings [3,4]. Implementation of the different technologies will be achieved to enhance the energy performance of the system as much as possible.
• Indoor air quality (IAQ). CO₂, atmospheric particulate, and VOC values are monitored to adjust natural/mechanical ventilation in the room when strictly necessary. This approach drastically reduces heat loss and increases the well-being of users.
• Acoustic comfort. Noise control is carried out externally to promote a healthier and more comfortable working environment. This implies a control on the opening of windows if noise pollution values are too high.
• Visual comfort. Lighting and solar radiation are integrated to guarantee visual and perceptual comfort to allow aspects related to the quality of the working space to be included. For example, a view towards the outside of the building can be favored when there is no glare inside.

These algorithms are designed to adapt dynamically the thresholds of the main comfort parameters (temperature and lighting) based on users’ discomfort feedback. Thanks to the adoption of a web app, the users can interact with the algorithms, identifying a status of discomfort. Such an approach overcomes a priori comfort threshold settings and considers the real condition of users. The application of advanced machine-learning models enables the system to provide the best possible regulations in terms of energy efficiency and comfort. In this perspective, the implementation of AI-based rules opens up interesting scenarios in addressing a still unsolved issue such as IEQ.

5. Discussion

To clarify the current state of the art for MF systems and define which aspects could facilitate their market adoption, an analytical assessment is carried out on issues dealt with during the design, manufacturing, and utilization stages. From this practical experience, two main issues clearly emerged.

On the one hand, the technical feasibility of advanced MF systems is confirmed. As demonstrated by several projects, the integration of active and passive technologies is no longer a technical barrier. Although the complexity of the integration largely depends on the type of technology to be embedded, a widespread knowledge of technical aspects and the high level of engineering of the façade companies allow for a wide degree of flexibility. In this regard, it is necessary to point out how the development of a supply chain capable of dialogue with designers and manufacturers could represent a pivotal aspect. This could also have direct effects on the reduction of costs related to MF systems, still considered one of the main barriers to widespread market adoption. The cost of the MEZEroE MF, also due to the ad hoc engineering of some components, is still high (ranging from 1000 to 1500 EUR/sqm), placing it in a narrow market niche and making it difficult to scale up on large building estates.

On the other hand, the novelty of this design lies in the integration of IoT and AI algorithms for façade automatization. Compared to previous MF projects, this study focuses more on new services enabled by data than on physical integration issues. Indeed, moving towards the digitalization of services, an IoT infrastructure for a building façade could increase product value through higher knowledge, flexibility, and customization.

Although these benefits are clarified, further analysis needs to be conducted to address the following issues:

• Design complexity. Developing a fully integrated IoT infrastructure in a building façade requires experts with cross-cutting skills during the design phase. In this context, the “engineer to order” type of manufacturing means that several design aspects have to be redesigned each time, increasing the complexity. Aspects related to the energy consumption, physical integration, aesthetics, maintenance, and cost-effectiveness of IoT infrastructure need to be considered according to the specific building requirements. To this end, further exploration in the development of modular and scalable IoT solutions must be carried out.
• Supply chain. The integration of IoT technologies in the MF systems expands the number of stakeholders involved during the design and manufacturing process. Today, the lack of professionals in the field of IoT automation for building systems causes a major difficulty in the development of non-standard projects. In the case of the MEZeroE prototype, three external developers (hardware developer, software developer and data communication in KNX, software developer and data communication in Mobdus) were involved in tackling a complex challenge.
• Interoperability. The interoperability with different technologies, design tools (e.g., BIM), and existing BMS is an aspect still to be solved. The lack of “plug & play” technologies for MF systems requires specific actors for collecting different data in a common data lake. This results in a constant commitment of IoT practitioners in the manufacturing and installation phases. In the MEZeroE prototype, setting up the communication system required more than a week’s work.
• Cost. Although the cost of individual sensors is limited compared to the cost of the façade, the development of a fully integrated IoT infrastructure is still an impactful factor in the market adoption of the technology. Due to a higher design complexity and the lack of ad hoc technologies for building façade products, the global cost of development of a customized infrastructure is still high. To address this issue, it will be necessary to develop modular low-cost technology and quantify the potential savings in economic terms.

6. Conclusions

After years of research and development in the field of MF systems, market adoption still seems far off. Although substantial funding at the European level has led to the validation of complex MF systems proving technical feasibility and high performance in terms of energy and IEQ, further steps need to be taken. To exploit the maximum market value of MFs, this paper has investigated the potential value added by the IoT and AI. As demonstrated in other sectors, IoT technologies are considered potential enablers to exploit the value of a product through greater customization, optimization, and the provision of new services. Through a real case study developed within the MEZeroE research project, technical, economic, and process issues in the design and use of a MF system with an on-board IoT infrastructure were investigated.

This experience showed how a lack of ready-to-market MF technologies is hampered by different issues. First of all, the construction market evolves and includes innovative products (only) if the market demands it. This means that the main barrier in the market deployment of MF lies in customers’ and developers’ lack of knowledge on advanced building envelopes that can guarantee high levels of comfort and energy efficiency. In this perspective, the development of real IoT-based prototypes is essential to collect data and consolidate knowledge.

To answer the objective of this paper, the authors can state that an integrated IoT infrastructure for MF, both hardware and software, is needed to exploit the maximum value of products. In addition to the product customization provided by digital services, the IoT enables the communication of different technologies, thus overcoming vertical and closed management of them. Such an approach allows for automated, optimal, and highly adaptive performance management of a complex product, providing clear benefits in terms of energy savings and IEQ levels. In this context, the potential widespread and unlimited application of AI for automation appears to be the most important value with the greatest prospects. Rule-based algorithms and machine-learning approaches can drastically revolutionize the way we regulate active and passive technologies in buildings, leading to higher levels of energy efficiency and IEQ. All these aspects could turn into significant value for the market deployment of MF products. However, further demonstrations of the benefits generated by the IoT and AI will need to be validated to make the market ripe for the application of innovative building skins. In conclusion, this research aimed to stimulate a debate on the future of MF systems, identifying a unique opportunity in digital technologies to make further progress in innovative façade systems that are able to assure high energy efficiency and IEQ standards.