Comprehensive Review of the Advancements, Benefits, Challenges, and Design Integration of Energy-Efficient Materials for Sustainable Buildings

Abstract

Energy-efficient materials are essential in buildings to reduce energy consumption, lower greenhouse gas emissions, and enhance indoor comfort. These materials help address the increasing energy demand and environmental impact of traditional construction methods. This paper presents a comprehensive literature review that explores advanced materials and technologies for improving building energy efficiency, sustainability, and occupant comfort. The study applies a comparative analysis of peer-reviewed research to examine key technologies analyzed include building-integrated photovoltaics, advanced insulating materials, reflective and thermal coatings, glazing systems, phase-change materials, and green roofs and walls. The study highlights the significant energy savings, thermal performance, and environmental benefits of these materials. By integrating these technologies, buildings can achieve enhanced energy efficiency, reduced carbon footprints, and improved indoor comfort. The findings underscore the potential of advanced building materials in fostering sustainable construction practices. The methodology of this review involves collecting, analyzing, summarizing, comparing and synthesizing existing research to draw conclusions on the performance and efficiency of these technologies.

1. Introduction

The rapid increase in population has led to the rise in demand for more buildings. This has also caused an increase in energy demand [1]. The majority of electricity is being produced from fossil fuels. Fossil fuels are becoming more expensive and also cause greenhouse gasses (GHGs), which are a major contributor to climate change [2]. The urgency of transitioning to energy-efficient building materials is underscored by global sustainability initiatives such as the Paris Agreement and the United Nations’ Sustainable Development Goals (SDGs), which emphasize the need to reduce carbon emissions, enhance energy efficiency, and promote sustainable development. The building sector is a significant contributor to global emissions and improving energy efficiency aligns with the targets set by these international frameworks, particularly SDG 7 (Affordable and Clean Energy) and SDG 13 (Climate Action).

Most buildings today are constructed using traditional materials such as bricks and cement. While these materials have been the standard for centuries, they are not energy-efficient [3]. Buildings made from these materials often require extensive heating and cooling to maintain comfortable indoor environments, leading to high energy consumption. This is not sustainable in the long term, especially given the growing concerns about energy costs and environmental impacts.

Recent advancements in technology have led to the development of new materials that can replace traditional building materials to enhance energy efficiency [4]. These innovative materials include building-integrated photovoltaics (BIPVs), advanced insulation, reflective coatings, high-performance glazing systems, phase-change materials (PCMs), and green roofs [5]. With the availability of these options, the real research question is “Can the integration of advanced materials and technologies, such as BIPVs, high-performance insulation, and green roofs, significantly reduce energy consumption and enhance sustainability in modern buildings?”. This review seeks to analyze the current literature and test the hypothesis that these technologies not only offer energy savings but also contribute to architectural integrity, esthetic appeal and functionality. Additionally, the adoption of these materials improves occupant thermal comfort by maintaining stable indoor temperatures, reducing temperature fluctuations, and improving air quality. Enhanced comfort, combined with lower energy costs, makes energy-efficient materials a critical investment in improving building performance and occupant satisfaction.

BIPVs are a technology that transforms traditional building parts into energy-generating components. In this system, special PV modules are used instead of windows, walls roofs, etc., removing the need for extra space required by traditional PV systems [6]. They also improve the esthetics of the building. Other examples include advanced insulation materials which provide higher thermal resistance compared to traditional insulation [7]. These include aerogels and vacuum insulation panels (VIPs). These materials control indoor temperatures while taking less energy input. This reduces the need for heating and cooling. Reflective coatings on roofs and walls also help in controlling the temperature by reflecting sunlight and heat away. High-performance glazing systems, including double-glazed and triple-glazed windows, as well as smart glass technologies, improve thermal performance and reduce energy loss through windows [8]. PCMs are another innovative solution, as they absorb and release thermal energy to help regulate indoor temperatures. Green roofs and walls not only provide insulation but also contribute to urban biodiversity and reduce the heat island effect in cities.

This study applies a comprehensive literature review methodology, gathering data from peer-reviewed journals, conference papers, and technical reports over the past decade. The analysis focuses on synthesizing findings on the energy-saving potential, environmental impact, and practical applications of advanced building materials and technologies. This allows for a critical comparison of various materials and their contributions to sustainable construction, providing insights into their benefits and limitations in modern buildings. The materials and technologies selected for this review were carefully chosen based on specific inclusion criteria. This includes materials widely researched in terms of energy efficiency, those currently available commercially, and those with demonstrated environmental benefits in peer-reviewed studies. Materials applicable to real-world construction projects were prioritized. Conversely, materials still in the conceptual phase or lacking sufficient data on energy performance, as well as those not easily integrated into modern building envelopes, were excluded from the review. Through this review, we aim to provide a comprehensive overview of the potential of these materials to revolutionize building construction by making it more energy-efficient and sustainable. The study discusses design considerations for incorporating these materials, their impacts, and the challenges and limitations associated with their use. The findings are intended to inform architects, builders, and policymakers about the latest advancements in energy-efficient building materials, empowering stakeholders to make informed decisions that contribute to greener and more sustainable buildings, ultimately reducing the building sector’s overall energy consumption and environmental impact.

2. Building-Integrated Photovoltaics in Buildings

BIPVs are an innovative approach that merges solar technology with traditional building materials. This combination allows for both energy generation and architectural integration [9]. BIPVs stand out due to their non-polluting nature, esthetic appeal, and modularity. Unlike traditional photovoltaic systems, which are typically mounted on rooftops, BIPVs replace conventional building components, integrating seamlessly into the building envelope. Both technologies differ significantly in their design, implementation, and overall impact on building architecture and functionality.

Table 1. Comparison between BIPV and Traditional PV Systems.

Aspect	BIPV Systems	Traditional PV Systems
Design and Integration	Seamless integration into building envelope	Add-on design, mounted on rooftops or ground
Esthetic Appeal	Customizable to match architectural style	Can compromise visual esthetics
Space Efficiency	Eliminates need for additional space	Requires additional land or roof space
Installation Complexity	More complex, integrated with construction process	Easier and quicker to install
Maintenance	More challenging, specialized skills required	Easier, straightforward maintenance
Efficiency	Varies, can improve thermal insulation	Higher efficiency, optimized modules
Initial Costs	Higher due to integration and complexity (USD 4.00 to USD 7.00 per watt)	Lower, standardized modules and processes (USD 2.50 to USD 3.50 per watt)
Long-Term Savings	Potential savings in materials and energy costs	Dependent on energy production and incentives
Environmental Impact	Promotes material efficiency, sustainable design	Reduces carbon emissions, potential land use impact

presents the comparison between both technologies. BIPVs include applications on façades, flat and curved roofs, and pitched and sloped roofs. The flexibility in design, color, and form factors allows architects to maintain and even enhance the building’s esthetics [6]. BIPVs require no extra space as they are directly installed in different parts of the building. This is beneficial in urban environments where space is limited. This direct integration also reduces cost by saving the requirement of extra construction materials. The multi-purpose nature of BIPVs also saves labor, installation and construction costs.

In terms of energy efficiency, BIPVs offer substantial improvements. By generating electricity on site, BIPVs reduce reliance on external power sources and minimize transmission losses. This on-site generation contributes to the building’s overall energy efficiency and sustainability. Additionally, BIPV materials can enhance the thermal insulation of buildings, further improving energy performance [6]. This dual functionality of energy generation and thermal insulation makes BIPVs highly effective in creating energy-efficient buildings.

BIPVs have varying recyclability depending on the materials used. Typically, components like glass and aluminum, which make up a significant portion of BIPVs, have high recycling rates of up to 85% and 95%, respectively. However, the recycling of photovoltaic cells, especially silicon-based cells, poses more challenges due to their integration with other materials. Current studies estimate that about 75% of the materials in BIPV systems can be recovered, with advancements in recycling technologies aimed at increasing this figure. Despite these challenges, the recyclability of BIPVs is improving as manufacturers prioritize sustainable designs to align with circular economy practices.

2.1. Applications of BIPVs in Construction Materials

This section explores the various applications of BIPVs in roofing, façades, windows, and shading devices, each offering unique advantages and applications in modern construction. Figure 1 shows a prototype building and the BIPV systems installed in it.

Table 2. Comparison of the different types of BIPV applications.

Integration Technique	Subsection	Material Composition	Replaces	Efficiency Range	Benefits	Challenges	Building
Solar Shingles	BIPVs in Roofing	Monocrystalline, polycrystalline, thin-film PVs	Asphalt shingles, traditional tiles	13–18%	Esthetic integration, space efficiency, durability	Higher cost, complex electrical integration	Hermitage Museum, Amsterdam
Solar Tiles	BIPVs in Roofing	Ceramic, slate, concrete with PVs cells	Traditional roofing tiles	10–17%	Esthetic appeal, design flexibility, durability	Higher cost, specialized installation	Tesla Solar Roof, USA
Photovoltaic Windows	BIPVs in Glass	Transparent, semi-transparent silicon, thin-film PVs	Conventional windows	5–15%	Esthetic flexibility, energy generation, transparency	Higher cost, precision manufacturing	EDGE Olympic, Amsterdam
Semi-Transparent PV Glass	BIPVs in Glass	Amorphous silicon, cadmium telluride, organic PV cells	Conventional glass elements	5–15%	Natural light, energy efficiency, architectural integration	Balancing transparency and efficiency	ECN Headquarters, Petten
PV Cladding	BIPVs in Façades	Crystalline silicon, thin-film PVs	Traditional cladding materials	10–18%	Energy generation, thermal and acoustic insulation	Higher initial cost, shading, orientation	CIS Tower, Manchester
Façade Integration	BIPVs in Façades	Crystalline silicon, thin-film PVs, perovskite	Conventional façade materials	10–20%	Seamless design, high energy output, esthetic appeal	Installation complexity, cost	Al Hamra Tower, Kuwait
PV Canopies and Awnings	Other Construction Elements	Tempered glass, polycarbonate with PV cells	Conventional canopies, awnings	10–20%	Shade, energy generation, cooling load reduction	Structural integration, cost	Blackfriars Station, London, and Health Center, North Carolina
PV Noise Barriers and Balconies	Other Construction Elements	Tempered glass, acrylic, composite panels with PV cells	Traditional noise barriers, balconies	10–18%	Noise reduction, energy generation, outdoor space	Installation complexity, cost	A9 Motorway, Netherlands and Soltag House, Denmark

summarizes the different types of BIPV applications discussed in this study.

When installing BIPVs, several design and technical considerations must be considered to ensure optimal performance and longevity are similar for all technologies involved. First, the orientation and tilt of the roof are critical. Ideally, the BIPVs should face south in the northern hemisphere (or north in the southern hemisphere) to maximize solar exposure [11]. The tilt angle should be optimized for the specific geographic location to capture the maximum amount of sunlight. Shading analysis is also essential. Identifying potential obstructions such as trees, chimneys, or nearby buildings that could cast shadows on the BIPVs is crucial, as shading can significantly reduce the efficiency of solar tiles. The structural integrity of the roof must be assessed to ensure it can support the additional weight of the BIPVs [12]. This may require reinforcing the roof framework, particularly in older buildings. The roof should be weatherproofed to stop water leakage. The BIPVs should be able to shed water and withstand extreme weather conditions.

Electrical integration and wiring are also very important as the system must be properly connected to the building’s electrical system [11]. Correct rated inverters and safety devices should be installed according to the electrical codes and standards. To stop overheating, proper ventilation is important to increase their efficiency and lifespan [11]. Proper airflow beneath the modules controls the operating temperatures. Esthetic integration is very vital for BIPVs. The BIPVs should be installed in such a manner that they improve the overall architectural style of the building, which includes its colors, textures, and shapes. The system should also have easy maintenance access for cleaning and repairing. The installation must comply with all relevant building codes, zoning laws, and regulatory requirements, including obtaining necessary permits and approvals from local authorities.

2.1.1. Solar Tiles: BIPVs in Roofing

Solar tiles are BIPVs that are used in place of traditional roofing materials to increase the esthetic and produce power from the sun, as shown in Figure 2 [13]. These solar tiles are made from monocrystalline or polycrystalline silicon. The silicon is encapsulated in a durable, weather-resistant layer to protect against the elements [14]. The tiles come in various shapes and sizes, designed to mimic traditional roofing materials like asphalt shingles, clay tiles, or slate. The dimensions of solar tiles can vary, but a standard size is approximately 12 inches by 86 inches. A typical solar tile may produce between 50 and 100 watts of power. They typically have an efficiency range of 10% to 17% [15]. Solar tiles are connected in series and parallel configurations to achieve the desired power output and voltage for the building. Solar tiles are suitable for both residential and commercial buildings. They are particularly advantageous for new constructions or when re-roofing existing buildings. This is because they serve the dual purpose of providing a weatherproof roof and generating electricity [16]. Solar tiles improve esthetic appeal by blending with the roof’s design and architecture. Solar tiles also improve the thermal insulation of roofs [6]. On average, solar tiles can cost between USD 20 and USD 25 per square foot, including installation. For a typical residential roof of 2000 square feet, the total cost can range from USD 40,000 to USD 50,000. However, this cost can be offset by energy savings over time and potential incentives or subsidies for renewable energy installations [16]. By integrating energy generation into the building structure, solar tiles help to lower greenhouse gas emissions and contribute to the building’s sustainability.

2.1.2. BIPVs in Glass

BIPVs in glass, specifically photovoltaic windows and semi-transparent PV glass as shown in Figure 3, represent a significant advancement in integrating renewable energy technology with building design. These technologies allow for the generation of electricity while maintaining the transparency and functionality of traditional windows [18]. Photovoltaic windows are designed to replace conventional windows in buildings. They come in various sizes and shapes, tailored to fit standard window dimensions. The power rating of photovoltaic windows varies depending on the technology and the size of the window. A typical photovoltaic window can generate between 100 and 200 watts per square meter. The efficiency of photovoltaic windows varies widely, from 5% for highly transparent modules to 15% for less transparent, more opaque modules [19].

Figure 4a shows the basic principle for PV windows. This variability allows for a range of applications, from fully transparent windows that provide minimal energy generation to semi-transparent or opaque windows that generate more electricity. This allows for more light to pass through while still generating electricity. Semi-transparent PV glass panels are typically available in sizes like standard window glass, with power ratings ranging from 50 to 150 watts per square meter, depending on their transparency level and the photovoltaic technology used. The cost of photovoltaic windows and semi-transparent PV glass varies widely based on the technology and installation complexity. On average, the price can range from USD 300 to USD 500 per square meter [22]. These windows also contribute to lowering the building’s carbon footprint by utilizing renewable energy sources [23].

He et al. evaluated amorphous silicon photovoltaic windows with ventilated cavities [24]. Their experiments indicated a 46.5% reduction in indoor radiative heat gain during summer, which contributed to better thermal comfort for building occupants. Li et al. studied CdTe-based BIPV windows, which offered seasonal regulation benefits and improved heat transfer performance, resulting in significant energy savings in both winter and summer [22]. Sun et al. investigated integrated semi-transparent cadmium telluride (CdTe) photovoltaic glazing in windows [25]. Their study showed notable improvements in energy and daylight performance for different architectural designs, suggesting that semi-transparent PV glazing can enhance both energy efficiency and occupant comfort.

2.1.3. BIPVs in Façades

BIPVs are used in façades, including building façade integration and PV cladding as shown in Figure 5 [26]. Building façade integration involves embedding photovoltaic modules directly into the building’s external walls. These modules are typically made from high-efficiency photovoltaic materials such as monocrystalline or polycrystalline silicon. They come in various shapes, sizes, and colors to match the building’s design. Standard modules can measure at around 1.6 m by 1 m and generate between 150 and 300 watts each. The efficiency of PV elements in building façades typically ranges from 11% to 18% [27]. These integrated façades are replacing conventional materials like concrete, glass, and metal panels. Figure 4c shows the basic principle for PV façades. PV cladding is another form of BIPVs that involves attaching photovoltaic panels to the building’s exterior. These panels can be installed over existing façades or used in new constructions. PV cladding panels are typically larger than those used in façade integration, with dimensions of around 1.7 m by 1 m, generating up to 350 watts per panel [28]. They are made from similar high-efficiency materials and can be customized to fit the building’s design requirements. PV cladding is used to replace traditional cladding materials, offering dual functions of energy generation and building protection.

These systems not only enhance the visual appeal but also makes use of vertical spaces that are often underutilized in conventional solar installations [29]. In terms of energy efficiency, BIPV façades generate electricity on site and enhance the thermal insulation of buildings. On average, the price can range from USD 250 to USD 450 per square meter. While the initial investment is higher compared to traditional façade materials, the long-term energy savings and potential incentives for renewable energy installations can offset these costs. Furthermore, BIPV façades contribute to lowering the building’s carbon footprint by utilizing renewable energy sources. The BIPV design and technical considerations must be considered when installing BIPV façades [30].

Figure 5. BIPVs in façades. (a) PV cladding [31], (b) building façade integration [32].

Figure 5. BIPVs in façades. (a) PV cladding [31], (b) building façade integration [32].

Nagy et al. proposed a dynamic BIPV façade with angularly variable PV modules [33]. The results showed that this variable BIPV façade could achieve 20–80% net energy savings compared to static PV shading devices. The environmental impact of this dynamic BIPV façade is reduced based on a whole life cycle analysis that considers dynamic energy savings. In another study, Yang et al. developed energy models for BIPV double-skin façades tailored to the Australian climate [34]. These models demonstrated that PV-DSFs could achieve energy savings of up to 106% depending on design parameters such as visible light transmittance, cavity thickness, and the window U-value as shown in Figure 6. The façades switch between external circulation, internal circulation, and thermal insulation modes, enhancing natural convection and increasing PV system power production.

2.1.4. Canopies and Awnings

Canopies and awnings integrated with photovoltaic technology, known as PV canopies and awnings as shown in Figure 7, are innovative solutions that combine the benefits of shading and renewable energy generation [34]. These structures are typically embedded in durable, weather-resistant layers to withstand environmental conditions. They can range from small awnings above windows and doors to large canopies covering patios, walkways, or parking areas. The dimensions of these structures can vary significantly, but a typical PV canopy might measure around 10 feet by 10 feet, with each module generating approximately 200 to 300 watts of power. The efficiency of these photovoltaic materials typically ranges from 15% to 20%, depending on the technology used [35]. Figure 4b shows the basic principle for awnings. An example of PV canopies in use is the Blackfriars Station in London, where a large PV canopy covers the station platform, generating significant amounts of electricity while providing shelter. A prominent example of PV awnings can be seen in the BIPV installation at the Federally Qualified Health Center in North Carolina, USA, where PV awnings contribute to the building’s energy needs and provide shaded areas for patients and staff.

PV canopies and awnings are installed in various locations on buildings, replacing traditional materials like metal, fabric, or glass [36]. These structures are especially beneficial in commercial buildings, schools, and residential properties where space for ground-mounted solar panels is limited. By incorporating PV technology into canopies and awnings, buildings can utilize vertical and horizontal spaces that would otherwise be underutilized. Mandalaki et al. explored thermochromic halide perovskite solar cells integrated into building materials [36]. These materials adapt to temperature changes, optimizing solar energy capture and providing significant energy savings through dynamic shading and insulation [36]. They provide shade, which can reduce cooling loads in adjacent indoor spaces, further enhancing energy efficiency [37]. On average, the price can range from USD 300 to USD 600 per square meter, including installation.

Figure 7. BIPVs in canopies and awnings. (a) Canopies [38], (b) awnings [39].

Figure 7. BIPVs in canopies and awnings. (a) Canopies [38], (b) awnings [39].

2.1.5. Noise Barriers and Balconies

Noise barriers and balconies integrated with photovoltaic technology represent innovative solutions for generating renewable energy while providing noise barriers and balconies as shown in Figure 8 [13,37]. An example of PV noise barriers is the A9 motorway in the Netherlands, where noise barriers integrated with PV cells generate electricity while reducing traffic noise. an example of PV balconies is the Soltag House in Denmark, where PV-integrated balconies contribute to the building’s overall energy generation.

PV noise barriers are designed to reduce noise pollution from traffic and other sources while generating electricity. PV noise barriers can vary in size, but a typical panel might measure at around 2 m by 1 m, generating between 200 and 300 watts of power. The efficiency of these photovoltaic materials usually ranges from 15% to 20%, depending on the technology used [13]. PV noise barriers are installed along highways, railways, and other noisy environments, replacing traditional noise barrier materials like concrete or metal. They provide the dual function of noise reduction and energy generation. PV balconies, on the other hand, are designed to replace traditional balcony materials. A typical balcony panel measures at around 1.5 m by 1 m. They generate between 150 and 250 watts of power. These balconies can be used in residential and commercial buildings, providing both outdoor space and energy generation. On average, PV noise barriers’ and balconies’ prices can range from USD 300 to USD 500 per square meter, including installation.

Table 3. Considerations for BIPV systems.

Consideration	Description	Requirements	Advantages	Disadvantages	Impact on Building Integrity	Buildings
Electrical Design	Addressing mismatches due to shading and orientation	Specialized module solutions, decentralized MPP tracking	Improved energy yield, reduced shading impact	Complex design and higher costs	Can enhance if designed properly	Swiss House of Natural Resources, Zurich, Switzerland
Mechanical and Structural	Ensuring structural integrity under environmental loads	Adequate framing and support	Maintains building integrity, adds structural strength	Potential for structural issues if not properly supported	Enhances if properly integrated	CIS Tower, Manchester, UK
Thermal Management	Managing heat buildup and thermal performance	Proper ventilation, materials with good thermal conductivity	Enhanced insulation, reduced heat gain	Risk of overheating	Can enhance thermal performance	BIQ House, Hamburg, Germany
Esthetic Integration	Blending PV modules with building architecture	Customization of module color, size, and shape	Maintains visual appeal, adds esthetic value	Customization can increase costs	Enhances visual appeal	Apple Park, Cupertino, USA
Economic and Regulatory	Assessing economic feasibility and regulatory compliance	Initial cost assessment, compliance with building codes	Long-term energy savings, potential incentives	Higher initial costs	Neutral to positive depending on economic factors	Solar Settlement, Freiburg, Germany
Orientation and Shading	Optimizing module orientation and minimizing shading impacts	Detailed planning of module placement	More uniform energy generation, increased efficiency	Requires careful planning and design	Enhances energy generation profile	Federation Square, Melbourne, Australia
Installation and Maintenance	Ensuring ease of installation and ongoing maintenance	Simplified installation processes, accessible design	Easier integration, lower maintenance costs	Potential for increased initial labor costs	Can enhance if maintenance is considered	De Rotterdam, Rotterdam, Netherlands

summarizes the challenges and considerations that are important for BIPV systems.

2.2. Challenges and Barriers to BIPV

While BIPVs offer numerous environmental, economic, and esthetic benefits, their widespread adoption faces several significant challenges and barriers. Critical barriers hinder the broader implementation of BIPV systems, including economic barriers, regulatory and policy issues. One of the primary economic barriers to BIPVs’ adoption is the high initial costs and investment required. BIPV systems generally have higher upfront costs compared to traditional PV systems due to the need for custom-designed modules and the integration into building materials. These costs can include the development and production of specialized PV modules, additional structural supports, and the installation process, which often requires skilled labor. For example, integrating PV glass into façades or designing custom solar shingles can be significantly more expensive than installing conventional solar panels on a roof. The price difference between traditional PV systems and BIPV systems is substantial. Traditional rooftop PV systems typically cost between USD 2.50 to USD 3.50 per watt installed, whereas BIPV systems can range from USD 4.00 to USD 7.00 per watt installed. A 5 kW PV system costs around USD 15,000, while the same rated BIPV system costs between USD 20,000 and USD 35,000. Due to the higher initial cost, many customers shy away from BIPVs and select PV systems to save on cost.

The market share of BIPV systems remains limited due to the technology being new. BIPVs are not yet produced on the same scale as PV systems. This has caused higher production costs and limited availability. This has also caused the limited use of BIPVs in regular homes and buildings, therefore also reducing their promotion. Although there are successful projects such as the Plus-Energy House in Stuttgart, Germany, and the Freiburg Solar Settlement, there are still limited examples in local communities. The overall adoption rate is lower than PV systems. Regulatory and policy issues also cause hurdles to the increase in BIPV systems. Building codes and standards vary between countries. This creates a complex regulatory landscape for BIPV integration. These codes do not consider the unique characteristics of BIPV systems. This creates challenges in obtaining the necessary approvals and certifications. These issues cause delays and increased costs for BIPV projects. Many governments offer incentives for PV systems and do not consider any special incentive for BIPV projects. Similarly, the feed-in tariffs, tax credits, and rebates are calculated based on PV systems, and do not consider the multifunctional nature of BIPVs. Moreover, inconsistent policies and incentives across different regions can create uncertainty for investors and developers, making it difficult to plan and execute BIPV projects.

Despite these challenges, there have been efforts to address regulatory and policy barriers to BIPV adoption. Some countries have started to develop specific guidelines and standards for BIPV systems. They aim at streamlining the approval process and providing clarity on compliance requirements. Additionally, certain governments have introduced targeted incentives for BIPV projects, recognizing their potential to contribute to sustainable urban development. The European Union has been active in supporting BIPVs through initiatives like the Horizon 2020 program, which funds research and development in innovative energy technologies, including BIPVs.

3. Insulating Materials

Insulating materials are essential components in building construction, designed to reduce the heat transfer between inside and outside environments [42]. They play a critical role in maintaining comfortable indoor temperatures, thereby minimizing the need for excessive heating or cooling. By improving a building’s thermal performance, insulating materials contribute significantly to energy efficiency, resulting in lower energy consumption and reduced utility costs [43]. Traditional building materials, such as bricks and concrete, possess a high thermal mass, which allows them to store and release heat slowly. While this can help stabilize indoor temperatures, improper use of high thermal mass materials can lead to increased energy consumption for heating and cooling, especially in climates with significant temperature fluctuations. Therefore, careful design and insulation are required to prevent unwanted heat gain or loss. The importance of insulating materials in buildings cannot be overstated. They help create a barrier that slows down the rate of heat flow, which is particularly crucial in regions with extreme temperatures. During the winter, insulation prevents heat from escaping, keeping the interior warm. Conversely, in the summer, it keeps the heat out, maintaining a cooler indoor environment. This thermal regulation not only enhances occupant comfort but also leads to substantial energy savings [44]. Moreover, effective insulation contributes to environmental sustainability. By reducing the energy required for heating and cooling, insulating materials help lower the greenhouse gas emissions associated with energy production. This reduction in carbon footprint aligns with global efforts to combat climate change and promotes the development of green buildings. In addition to thermal benefits, insulating materials also provide soundproofing, enhancing the acoustic comfort within buildings. They can reduce noise transmission between rooms and from external sources, creating a quieter and more peaceful indoor environment. Overall, the use of insulating materials is a fundamental aspect of modern building design, aimed at achieving energy efficiency, environmental sustainability, and enhancing occupant comfort.

3.1. Applications of Insulating Materials in Construction Materials

This section explores the various applications of insulating materials such as aerogels, foam insulations, fiber insulations, and barriers, each offering unique advantages and applications in modern construction.

Table 4. Types of insulation applications.

Insulation Type	Subsection	Material Composition	Replaces	Properties	Thermal Conductivity	Benefits	Challenges
Aerogels	Advanced Insulating Materials	Silica	Fiberglass, foam	Highly porous, lightweight	0.015 W/m·K	Superior insulation, space-efficient	High cost, fragile
VIPs	Advanced Insulating Materials	Fumed silica in metalized film	Polystyrene, polyurethane foam	Thin, flat, rigid	0.004 W/m·K	High efficiency, minimal thickness	High cost, careful handling required
Spray Foam Insulation	Foam Insulations	Polyurethane or polyisocyanurate	Fiberglass batts, loose-fill insulation	Expands and hardens	0.020 W/m·K	Airtight seal, structural support	Proper mixing and application needed
Rigid Foam Boards	Foam Insulations	Polyisocyanurate, XPS, EPS	Fiberglass, cellulose insulation	Rigid, various thicknesses	0.022–0.032 W/m·K	High insulation value, moisture-resistant	Proper cutting and fitting needed
Fiberglass Insulation	Fiber-Based Insulations	Glass fibers	Loose-fill cellulose, foam insulation	Fine glass fibers	0.043 W/m·K	Affordable, easy to install	Health risks if not handled properly
Cellulose Insulation	Fiber-Based Insulations	Recycled paper products	Fiberglass, foam insulations	Loose-fill or dense-pack	0.040 W/m·K	Eco-friendly, good sound insulation	Even distribution required
Mineral Wool	Fiber-Based Insulations	Natural rock or industrial slag	Fiberglass, foam	Batts, rolls, loose-fill	0.038 W/m·K	Fire-resistant, sound insulation	Proper fit to prevent gaps
Radiant Barriers	Radiant Barriers	Aluminum foil	Traditional insulation materials	Reflects radiant heat	Reflects up to 97% radiant heat	Reduces cooling loads	Requires air space, proper ventilation
Nanomaterial	Emerging Insulating Materials	Carbon nanotubes, graphene, silica aerogels	Fiberglass, foam	Nanoscale structure, high surface area	0.005–0.01 W/m·K	Superior performance in thin layers	High cost, production scalability
Biomaterial	Emerging Insulating Materials	Hemp, flax, mycelium	Fiberglass, foam	Biodegradable, renewable	0.040 W/m·K	Eco-friendly, recyclable, non-toxic	Variability in performance, quality control

summarizes the different types of insulation applications discussed in this study.

3.1.1. Advanced Insulating Materials

Advanced Insulating Materials include Aerogels and Vacuum Insulation Panels (VIPs) as shown in Figure 9. Aerogels are highly porous and lightweight materials known for their exceptional thermal insulation properties [45]. They are primarily made from silica, although other materials like carbon and metal oxides can also be used. Aerogels have a unique structure composed of over 90% air, which contributes to their low thermal conductivity, often as low as 0.015 W/m·K. This makes them one of the most effective insulating materials available [46]. Aerogels typically come in the form of blankets, sheets, or particles, with sizes and shapes customizable to fit specific applications. In building construction, aerogels are used in walls, roofs, and windows where high thermal performance is required but space is limited. They replace traditional insulation materials like fiberglass and foam, providing superior insulation with much thinner layers. The benefits of using aerogels in buildings are significant.

Carroll. Et al. conducted a comprehensive study on the use of monolithic aerogel in building applications [49]. Their research demonstrated that aerogels offer exceptional thermal and acoustic performance, significantly reducing heating and cooling losses in residential buildings. The study also found that incorporating artistic effects such as dyes and laser etching into aerogel-based glazing systems improved esthetics while maintaining high visible light transmission. This indicates that aerogels can effectively enhance energy efficiency in buildings by reducing heat transfer and providing additional benefits such as improved indoor acoustic comfort. Despite their high initial cost, which ranges from USD 20 to USD 30 per square foot, the long-term energy savings can justify the investment. Aerogels are also non-combustible and provide good acoustic insulation [50]. When installing aerogels, several design and technical considerations must be considered. The installation process should ensure that the aerogel material is evenly distributed to avoid thermal bridging. Proper sealing is necessary to maintain the insulating properties and prevent moisture ingress, which can degrade the material’s performance. Additionally, handling aerogels requires care, as they are fragile and can produce dust that may be harmful if inhaled. Aerogels, particularly silica-based aerogels, have limited recyclability due to their complex structure and production process. While silica, the primary component, is an abundant and non-toxic material, the recycling process for aerogels is not well-developed, and most aerogels are currently not recycled at the end of their lifecycle. However, some advancements are being made in this area. Up to 50–60% of the raw materials in aerogels can be recovered through chemical recycling processes. Despite this, the high cost and energy requirements of recycling aerogels make it less economically feasible at present. Efforts are ongoing to improve the sustainability of aerogel production and enhance their end-of-life recyclability.

VIPs are another advanced insulating material offering high thermal efficiency. VIPs are thin, flat panels with a rigid core material encased in an airtight envelope [51]. The core is usually made from a porous substance like fumed silica, and the envelope is typically a metalized film. VIPs have extremely low thermal conductivity, often around 0.004 W/m·K, making them highly efficient insulators. These panels are available in various sizes and shapes, typically ranging from 1 cm to 5 cm in thickness [52]. VIPs are used in building applications where space is at a premium, such as in walls, roofs, and floors. They replace conventional insulation materials like polystyrene and polyurethane foam, providing much better thermal performance with thinner profiles. They are ideal for retrofitting existing buildings where additional space for insulation is limited. VIPs also offer long-term performance stability if the vacuum seal is maintained. The cost of VIPs ranges from USD 8 to USD 15 per square foot, reflecting their advanced technology and high efficiency [53]. Installing VIPs requires careful planning and execution. The panels must be handled with care to avoid puncturing the vacuum seal, which would significantly reduce their effectiveness. Proper edge sealing and protection against mechanical damage are essential to ensure the longevity of VIPs. Additionally, incorporating VIPs into building designs should consider potential thermal bridging at the panel joints, which can be mitigated with appropriate detailing and insulation techniques. VIPs pose significant challenges for recyclability due to their multi-layered construction. While the fumed silica core is non-toxic and theoretically recyclable, separating it from the barrier films, which often consist of multiple layers of aluminum, plastic, and other composites, is technically difficult and not cost-effective. Current recycling efforts focus mainly on reusing the core material, which accounts for about 70% of the panel’s volume. However, the barrier film and the complex manufacturing process limit the overall recyclability of VIPs to less than 40%. Improvements in VIP design are being explored to enhance recyclability by using fewer complex materials and more easily separable components, thus aligning VIPs more closely with sustainable construction goals.

3.1.2. Foam Insulations

Foam insulations come in various forms, including spray foam insulation and rigid foam boards as shown in Figure 10, each with unique characteristics and applications. Spray foam insulation is created by mixing two chemical components that react and expand to form a rigid foam [54]. This foam is typically made from polyurethane or polyisocyanurate, and it has excellent thermal insulation properties, with a thermal conductivity of about 0.020 W/m·K. Spray foam is applied as a liquid, which then expands and hardens, filling gaps and creating an airtight barrier. It provides an airtight seal that reduces air infiltration, which is a common source of energy loss in buildings. Spray foam insulation also improves the structural integrity of buildings by adding rigidity to walls and roofs [55]. Despite its higher cost, ranging from USD 1 to USD 3 per square foot, the long-term energy savings and durability can offset the initial investment. When installing spray foam insulation, several design and technical considerations must be considered. Proper mixing and application are critical to ensure the foam expands correctly and adheres to surfaces. It is essential to follow safety guidelines, as the chemicals used can be hazardous if not handled properly. Ventilation during installation is crucial to avoid inhaling fumes, and protective gear should be worn. Additionally, ensuring that the foam does not over-expand and cause structural damage is important. Spray foam insulation presents significant recyclability challenges due to its chemical composition and application method. Once applied, spray foam insulation hardens into a rigid structure that is difficult to break down and separate from other building materials. As a result, it is rarely recycled, and most often ends up in landfills at the end of its life cycle. While the mechanical recycling of spray foam into lower-grade products is possible, it is not widely practiced due to economic and logistical challenges. Some efforts are being made to explore chemical recycling methods, where the foam is broken down into its raw components, but these processes are still in their early stages and are not yet commercially viable. Overall, the recyclability of spray foam insulation remains limited, and its disposal often presents environmental concerns.

Buratti et al. investigated spray foam insulation, highlighting its superior thermal resistance and air sealing properties compared to traditional materials [58]. Spray foam insulation provides an airtight seal that reduces air infiltration, which is a common source of energy loss in buildings. This reduction in air leakage can lead to significant energy savings, with some studies reporting a decrease in heating and cooling energy usage by up to 50%. Furthermore, spray foam insulation enhances the structural integrity of buildings, making it a valuable material for both new constructions and retrofits.

Rigid foam boards are another popular form of foam insulation. These boards are manufactured from materials such as polyisocyanurate, extruded polystyrene (XPS), and expanded polystyrene (EPS) [59]. Polyisocyanurate boards have a thermal conductivity of about 0.022 W/m·K, that of XPS is about 0.029 W/m·K, and that of EPS is about 0.032 W/m·K. These rigid foam boards were also examined by Buratti, et al. These materials are noted for their high insulation value and ability to reduce thermal bridging, thereby improving the overall thermal performance of building envelopes [58]. These boards come in various sizes and thicknesses, typically ranging from 1 to 4 inches in thickness, and they are used in walls, roofs, and foundations. They provide continuous insulation, reducing thermal bridging, which is the transfer of heat through structural elements like studs and joists. This improves the overall thermal performance of the building envelope. Rigid foam boards are also moisture-resistant, preventing issues related to water infiltration and mold growth [60]. The cost of rigid foam boards varies, with EPS being the least expensive at around USD 0.30 to USD 0.50 per square foot, XPS being around USD 0.42 to USD 0.70 per square foot, and polyisocyanurate being the most expensive at USD 0.70 to USD 1.00 per square foot. When installing rigid foam boards, it is important to ensure that they are properly cut and fitted to avoid gaps that could reduce their effectiveness. Sealing the edges and joints with appropriate materials, such as foam sealant or tape, is necessary to prevent air leakage. Additionally, proper attachment methods should be used to secure the boards in place, especially in areas prone to high winds or seismic activity. Care should also be taken to avoid compressing the foam, as this can decrease its insulating properties. Rigid foam boards offer moderate recyclability, with some foam types more easily recyclable than others. EPS is the most recyclable among these, with established recycling processes in place. It can be ground into small beads and reused in products like insulation or packaging materials. Recycling rates for EPS can reach up to 60–70% in some regions. XPS, on the other hand, is more challenging to recycle due to its denser structure and the presence of additives. However, mechanical recycling is possible, where the material is shredded and repurposed, although it is less widespread. PIR boards are more difficult to recycle due to their complex chemical composition. While some research is being conducted on chemical recycling methods for PIR, its recyclability remains limited, and most of these materials end up in landfills. Efforts are ongoing to improve recycling technologies for rigid foam boards to reduce their environmental impact.

3.1.3. Fiber-Based Insulations

Fiber-based insulations are a category of insulating materials that include fiberglass insulation, cellulose insulation, and mineral wool as shown in Figure 11. Fiberglass insulation is made from fine glass fibers. It comes in various forms, including batts, rolls, and loose-fill forms. Bjarløv et al. conducted a study on fiberglass insulation, emphasizing its affordability and ease of installation [61]. The study found that fiberglass has a thermal conductivity of approximately 0.043 W/m·K, making it an efficient material for reducing heat transfer in buildings. Fiberglass is typically used in walls, roofs, and attics, replacing traditional materials like loose-fill cellulose and foam insulation. The batts and rolls are available in standard sizes to fit between wall studs, joists, and rafters, usually ranging from 16 to 24 inches in width and 8 to 24 feet in length. The cost of fiberglass insulation is relatively low, ranging from USD 0.40 to USD 0.50 per square foot. The benefits of fiberglass insulation include its affordability, availability, and ease of installation. It provides good thermal resistance, helping to maintain indoor temperatures and reduce energy consumption for heating and cooling. Additionally, fiberglass insulation has sound-absorbing properties, which can enhance the acoustic comfort within buildings. However, proper handling is essential when installing fiberglass insulation, as the fine fibers can cause skin irritation and respiratory issues if inhaled. Protective clothing, gloves, and masks should be worn during installation to mitigate these risks. Fiberglass insulation is partially recyclable, with the glass fibers being the main component that can be recovered and reused. Fiberglass insulation is made from sand and recycled glass, with recycled content often making up between 20 and 30% of the product. Once fiberglass insulation has reached the end of its life, it can be ground down and remelted to produce new fiberglass products, including new insulation or other fiberglass-based materials. However, the process of recycling fiberglass insulation is not widely practiced due to contamination with binders, resins, or other construction debris, which complicates the recycling process. Additionally, the cost and energy required to recycle fiberglass often outweigh the economic benefits, leading most used fiberglass insulation to be sent to landfills.

Cellulose insulation is made from recycled paper products treated with fire-retardant chemicals [62]. It is available in loose-fill or dense-pack forms. The research by Tronchin et al. explored cellulose insulation, which is made from recycled paper products treated with fire-retardant chemicals [63]. This material provides good thermal and acoustic insulation, with a thermal conductivity of about 0.040 W/m·K. Cellulose insulation is commonly used in attics and wall cavities, providing an eco-friendly alternative to fiberglass and foam insulations. The loose-fill form is blown into place using special equipment, allowing it to fill gaps and voids effectively [64]. The cost of cellulose insulation ranges from USD 0.30 to USD 0.40 per square foot, making it an affordable and environmentally friendly option. The benefits of cellulose insulation include its high recycled content and ability to provide excellent thermal and acoustic insulation. It is also effective at reducing air infiltration, helping to create a more airtight building envelope. When installing cellulose insulation, it is important to ensure even distribution and adequate density to prevent settling over time, which could reduce its insulating effectiveness. Proper ventilation should be maintained during installation to avoid inhaling dust particles. Cellulose insulation is one of the most recyclable and sustainable insulation materials available. Made primarily from recycled paper products (often 80–85% recycled content), it is inherently eco-friendly. At the end of its life, cellulose insulation can be recycled again into s new insulation material or repurposed for other uses, such as mulch or compost, due to its biodegradable nature. Additionally, cellulose insulation does not require complex chemical processes for recycling, making it relatively easy and cost-effective to recycle. However, in practice, most cellulose insulation is not recycled at the end of its lifecycle due to contamination from other building materials. Despite this, its high recycled content and biodegradable properties make it one of the most environmentally sustainable insulation options available.

Figure 11. Fiber-based insulating materials in buildings. (a) Fiberglass insulation [65], (b) cellulose insulation [66], (c) mineral wool [67].

Figure 11. Fiber-based insulating materials in buildings. (a) Fiberglass insulation [65], (b) cellulose insulation [66], (c) mineral wool [67].

Mineral wool, another fiber-based insulation, was also analyzed by Bjånesøy et al. Made from natural rock or industrial slag, mineral wool has a thermal conductivity of about 0.038 W/m·K [61,68]. It is available in batts, rolls, and loose-fill forms and is used in walls, roofs, and floors. The batts and rolls are typically sized to fit between standard framing dimensions, like fiberglass insulation [69]. The cost of mineral wool ranges from USD 0.80 to USD 1.00 per square foot. The benefits of mineral wool insulation include its durability, moisture resistance, and superior fire resistance. It provides good thermal insulation, contributing to energy savings and enhanced comfort within buildings. Mineral wool is also resistant to mold and mildew, making it suitable for use in areas prone to moisture. When installing mineral wool, it is important to ensure a snug fit to prevent gaps that could compromise its insulating properties. Proper protective gear should be worn to avoid skin irritation from the fibers. Mineral wool is moderately recyclable. It is made from natural materials like basalt, and industrial byproducts such as slag, which are melted and spun into fibers. While mineral wool can be recycled, the process is less common due to the complexity of separating it from other construction materials after use. However, some manufacturers are beginning to reclaim mineral wool scraps from construction and demolition sites to produce new insulation products, with typical recycled content ranging from 20 to 40%. The primary challenge lies in contamination from binders and adhesives, which complicates recycling. Despite these obstacles, mineral wool is considered an eco-friendly material because it can be reused in new insulation production, helping to reduce waste and promote circular economy practices in building materials.

3.1.4. Radiant Barriers

Radiant barriers are a type of insulating material designed to reflect radiant heat rather than absorb it, making them particularly effective in hot climates where cooling loads are significant. They are typically made from a highly reflective material, usually aluminum foil, which is applied to one or both sides of a substrate like kraft paper, plastic film, or cardboard [70]. Radiant barriers are usually installed in attics, just under the roof as shown in Figure 12. They come in rolls or sheets, which are easy to cut and fit to the desired size and shape. The dimensions of these materials vary, but they generally come in widths ranging from 16 to 48 inches and lengths of up to 250 feet. Zhu et al. investigated the effectiveness of radiant barriers in reducing cooling loads [70]. Their research demonstrated that radiant barriers can reflect up to 97% of radiant heat, lowering attic temperatures by up to 30 degrees Fahrenheit. The study found that radiant barriers could reduce cooling costs by 5–10% in hot climates. Proper installation, including maintaining an air space and ensuring adequate ventilation, is crucial for maximizing the performance of radiant barriers.

They are also relatively inexpensive, with costs ranging from USD 0.10 to USD 0.25 per square foot [71]. Radiant barriers can be used in conjunction with other types of insulation, enhancing the overall thermal performance of the building envelope. When installing radiant barriers, several design and technical considerations must be considered. The effectiveness of a radiant barrier depends on the presence of an air space facing one side of the reflective surface. This air space is necessary to prevent heat conduction, which would otherwise negate the reflective properties of the material. Therefore, it is crucial to ensure that the barrier is not in direct contact with other materials, such as roof decking or insulation. Proper ventilation is also essential to maximize the performance of radiant barriers. Ventilation helps to carry away the heat that is reflected by the barrier, maintaining a cooler attic environment. Additionally, radiant barriers should be installed with the reflective side facing downwards in attic applications to prevent dust accumulation, which can reduce their reflective efficiency over time. They do not replace the need for thermal insulation but rather complement it by addressing radiant heat transfer. Radiant barrier insulation is highly recyclable. Aluminum, the primary component of radiant barriers, has a high recycling rate, with up to 95% of its material being recyclable without losing quality. This makes radiant barriers an environmentally friendly option, as the aluminum can be reclaimed and repurposed at the end of its life. However, radiant barriers are often combined with other materials like paper or plastic substrates, which can complicate the recycling process. The separation of these layers can be labor-intensive and is not always feasible. While the aluminum component is easily recyclable, these mixed-material barriers often end up in landfills unless the aluminum can be effectively separated.

Figure 12. Radiant barrier insulation in buildings [72].

Figure 12. Radiant barrier insulation in buildings [72].

3.1.5. Emerging Insulating Materials

Emerging insulating materials include nanomaterial-based insulation and biomaterial-based insulation. Nanomaterial-based insulation includes silica aerogels infused with carbon nanotubes or graphene. These materials have an extremely high surface area due to their nanoscale structure, allowing them to trap air effectively and drastically reduce heat transfer. Nanomaterial-based insulations exhibit thermal conductivities as low as 0.005–0.01 W/m·K, significantly lower than traditional materials like fiberglass or foam [55]. Nanomaterial-based insulation is used in applications where high-performance insulation is required in thin layers. These provide superior insulation with minimal thickness. The high cost, currently ranging from USD 30 to USD 50 per square foot, is a limitation, but as production scales up, prices decrease, making these materials more accessible for widespread use in sustainable construction projects.

Biomaterial-based insulation includes renewable resources such as hemp, flax, and mycelium. These materials have a lower environmental footprint, as they are biodegradable, require less energy to produce, and can be sourced locally [56]. Hemp-based insulation has a thermal conductivity of around 0.040 W/m·K, making it comparable to traditional insulating materials. The key benefits of biomaterial-based insulation include its recyclability and minimal environmental impact throughout its life cycle. Additionally, these materials are non-toxic, making them safer for indoor air quality compared to synthetic insulations. The cost of biomaterial-based insulation is competitive, typically ranging from USD 0.50 to USD 1.00 per square foot, depending on the material and its source. Challenges include ensuring consistent quality and performance, as natural materials can vary in their insulating properties. However, as sustainable construction becomes a priority, biomaterial-based insulation offers an effective solution for environmentally conscious building designs.

Table 5. Challenges and considerations important for insulation systems.

Consideration	Description	Requirements	Installation Difficulty	Advantages	Disadvantages	Impact on Building
Orientation and Shading Analysis	Ensuring optimal placement for efficiency	Proper alignment with sun exposure	Moderate	Maximizes efficiency	Complex planning required	Improved energy efficiency
Structural Integrity	Assessing if the structure can support weight	Reinforcement if needed	High	Ensures safety and performance	Potential need for reinforcement	Increased structural safety
Weatherproofing and Durability	Preventing water infiltration and ensuring longevity	Sealing and protective measures	High	Extends material life	Additional sealing costs	Enhanced durability
Electrical Integration	Correct wiring and compliance with codes	Using appropriate materials and methods	High	Enhances performance and safety	Requires skilled labor	Improved functionality
Maintenance Access	Allowing for regular maintenance and cleaning	Easy access points	Low	Ensures optimal performance	Possible additional costs	Sustained performance
Esthetic Integration	Matching with building’s overall style	Consistent design elements	Moderate	Enhances visual appeal	Potential design constraints	Enhanced esthetics
Safety Guidelines	Handling and installation safety	Use of protective gear	High	Prevents health risks	Increased initial costs	Safe and compliant installation
Cost–Benefit Analysis	Evaluating long-term benefits and costs	Detailed financial assessment	Moderate	Informs decision-making	Time-consuming analysis	Informed investment choices

summarizes the challenges and considerations important for insulation systems.

4. Coatings

Coatings are essential components in building construction, designed to enhance the performance and longevity of building surfaces. They play a critical role in protecting buildings from environmental elements, improving thermal efficiency, and enhancing esthetics [73]. By applying specialized coatings, buildings can achieve better energy efficiency, reduced maintenance costs, and improved durability. The importance of coatings in buildings cannot be overstated. They help create a barrier that protects against environmental damage, improves energy efficiency, and enhances the overall appearance of the building. During the winter, coatings with thermal properties prevent heat from escaping, keeping the interior warm. Conversely, in the summer, they help to keep the heat out, maintaining a cooler indoor environment. This thermal regulation not only enhances occupant comfort but also leads to substantial energy savings [74]. Moreover, effective coatings contribute to environmental sustainability. By reducing the energy required for heating and cooling, coatings help lower the greenhouse gas emissions associated with energy production. This reduction in the carbon footprint aligns with global efforts to combat climate change and promotes the development of green buildings. In addition to thermal benefits, coatings also provide protection against moisture, UV radiation, and physical wear, thereby preserving the structural integrity and esthetic appeal of buildings.

4.1. Applications of Coating Materials in Construction Materials

This section explores the various applications of coating materials such as reflective coatings, thermal barrier coatings, and ceramic coatings, with each offering unique advantages and applications in modern construction.

Table 6. Types of coating applications.

Coating Type	Material Composition	Replaces	Properties	Efficiency	Benefits	Challenges
Reflective Coatings	Acrylic, silicone, polyurethane with reflective pigments	Traditional roofing materials like dark asphalt shingles	High solar reflectance	Reflects up to 85% of solar radiation	Reduces cooling load, lowers roof temperature	Proper surface preparation, weather conditions during application
Thermal Barrier Coatings	Advanced ceramics like zirconia, alumina	Traditional insulation materials	Low thermal conductivity, high thermal resistance	Improves thermal resistance by up to 30%	Maintains stable indoor temperatures, reduces heat loss and gain	Proper surface preparation, curing process, application guidelines
Ceramic Coatings	Ceramic particles like silicon dioxide, titanium dioxide, aluminum oxide in binders like acrylic, epoxy, silicone	Traditional paints and coatings	High thermal resistance, durability, UV resistance	Reflects up to 90% of solar radiation	Reduces heat gain, protects against environmental elements	Proper surface preparation, curing process, application under appropriate conditions

summarizes the different types of coating applications discussed in this study.

4.1.1. Reflective Coatings

Reflective coatings are specialized treatments applied to building surfaces to reflect more sunlight and absorb less heat. They are designed to enhance the energy efficiency of buildings by reducing heat gain [75]. Reflective coatings can be applied to both roofs and walls, significantly lowering the overall cooling load and contributing to a more comfortable indoor environment. Figure 13 shows a reflective coating applied to the roof of a building. Reflective roof coatings are typically made from materials such as acrylic, silicone, or polyurethane, mixed with reflective pigments that enhance their ability to reflect sunlight. These coatings are available in various forms, including liquids, which can be applied with a brush, roller, or spray, and pre-fabricated sheets. The primary property of reflective roof coatings is their high solar reflectance, with some coatings being capable of reflecting up to 85% of solar radiation [76].

Reflective wall coatings are formulated for vertical surfaces. They contain reflective pigments to maximize sunlight reflection. These coatings can be applied to exterior walls to reduce heat gain and improve the thermal performance of the building envelope [78]. The efficiency of reflective coatings in reducing heat gain can be quantified by their Solar Reflectance Index (SRI), which measures a material’s ability to reflect solar heat and emit absorbed heat. Higher SRI values indicate better performance. Reflective coatings with high SRI values can lower roof and wall temperatures by up to 50 °F (28 °C), significantly reducing the cooling load on HVAC systems. This can lead to energy savings of up to 20% in cooling costs. Reflective coatings have been widely studied for their ability to reduce heat gain in buildings. A study by Iván Hernández-Pérez et al. examined the thermal behavior of concrete slab roofs with traditional and solar reflective coatings in Mexico [79]. The study demonstrated that white roofs without insulation had an exterior surface temperature that was between 11 and 16 °C lower than gray roofs without insulation, reducing the daily heat gain by 41–54%. When insulation was added, white roofs further reduced exterior surface temperatures by 17–21 °C compared to gray roofs, resulting in daily heat gains that were 37–56% smaller than the control case as shown in Figure 14. Reflective roof coatings present challenges in recyclability due to their composite nature. Once applied, these coatings form a permanent layer on the roof surface, making separation and recycling difficult. The presence of reflective additives like titanium dioxide and aluminum further complicates the process. As a result, reflective coatings are typically not recyclable, with most material ending up in landfills after removal. Efforts to improve sustainability focus on developing eco-friendly formulations, but current recycling options for these coatings remain limited.

Reflective coatings replace dark asphalt shingles or uncoated concrete. The benefits of using reflective coatings include improved thermal comfort, lower energy bills, and extended lifespans of roofing and wall materials due to reduced thermal stress [80]. The cost of reflective coatings can vary depending on the type and application method, with prices ranging from USD 0.75 to USD 3.00 per square foot. Despite the initial cost, the long-term energy savings and reduced maintenance costs make reflective coatings a cost-effective solution. When installing reflective coatings, several design and technical considerations must be considered. The surface preparation is crucial for ensuring the proper adhesion and performance of the coating. This may involve cleaning, repairing any damage, and applying a primer if necessary. The application process must follow the manufacturer’s guidelines to achieve the desired thickness and coverage. Additionally, the weather conditions during application, such as the temperature and humidity, can affect the curing process and the overall effectiveness of the coating.

4.1.2. Thermal Barrier Coatings

These coatings are typically made from advanced ceramics with low thermal conductivity, which helps to insulate the building and improve its energy efficiency [81]. Thermal barrier coatings are composed of materials such as zirconia, alumina, and other ceramic compounds that can withstand high temperatures and thermal cycling. These materials are often applied in layers, with the top layer being a ceramic coating and an underlying bond coat that adheres to the building surface. The coatings are available in various thicknesses, usually ranging from a few micrometers to several millimeters, depending on the application and desired level of insulation. Figure 15 shows thermal barrier coatings applied to the wall of a building. This makes them highly efficient at maintaining stable indoor temperatures, regardless of external weather conditions [82]. For instance, a well-applied TBC can significantly lower heat loss during winter and reduce heat gain during summer, thereby minimizing the need for additional heating and cooling. Studies have shown that TBCs can improve the thermal resistance of building components by up to 30%, leading to substantial energy savings. A study by Lu et al. focused on the effectiveness of heat-reflective coatings in urban areas to combat the urban heat island (UHI) effect [83]. The research showed that reflective coatings could effectively reduce the surface temperatures of pavements by increasing the surface albedo. Concrete samples with heat-reflective coatings were about 1 °C cooler, while asphalt samples were nearly 5 °C cooler on average compared to non-coated samples as shown in Figure 16. Research on infrared reflective coatings, such as the study by Mara et al., demonstrated that these coatings could significantly decrease surface temperatures by reflecting infrared light [84]. The study developed coatings with infrared reflective pigments that reduced heat absorption, resulting in lower surface temperatures and improved energy efficiency in buildings, as shown in Figure 17. The coatings were shown to reduce the need for air conditioning, thereby decreasing energy consumption and operating costs.

Generally, their cost ranges from USD 5 to USD 20 per square foot, making them a higher initial investment compared to traditional insulation materials. When installing thermal barrier coatings, proper surface preparation is crucial for adhesion and effectiveness, which may involve cleaning, repairing any damage, and applying a suitable primer. The application process must follow precise guidelines to achieve uniform coverage and the desired thickness. Additionally, the curing process, which allows the coating to harden and bond with the substrate, is critical for achieving maximum thermal resistance. Environmental conditions during application, such as temperature and humidity, can also affect the performance of thermal barrier coatings. Therefore, it is essential to follow the manufacturer’s recommendations for optimal results. Regular inspections and maintenance are necessary to ensure the coating remains intact and effective over time. Thermal barrier coatings have limited recyclability due to their strong adhesion and composite structure, often consisting of ceramic or polymer-based materials. These materials are difficult to separate from the underlying surface, making recycling impractical. Currently, most TBCs are discarded during renovation or demolition, and recycling options are minimal. While research is ongoing to improve their sustainability, the recyclability of thermal barrier coatings remains a significant challenge.

4.1.3. Ceramic Coatings

These coatings are made from ceramic particles suspended in a binder, which creates a tough, protective layer when applied to surfaces, as shown in Figure 18 [86]. Ceramic coatings are composed of fine ceramic particles such as silicon dioxide, titanium dioxide, and aluminum oxide. These particles are mixed with binders like acrylic, epoxy, or silicone to form a durable coating [87]. The coatings can be applied in various thicknesses, typically ranging from a few micrometers to several millimeters, depending on the desired level of protection and insulation. They are available in liquid form, which can be applied using brushes, rollers, or sprays, making them versatile for different application methods. The primary properties of ceramic coatings include high thermal resistance, excellent durability, and resistance to UV radiation, moisture, and chemicals. Ceramic coatings can reduce surface temperatures by reflecting up to 90% of solar radiation, significantly lowering heat gain and improving indoor thermal comfort. Ceramic coatings are used in various building applications, including exterior walls, roofs, and even interior surfaces. They replace traditional paints and coatings that may not offer the same level of protection and insulation.

Generally, the cost ranges from USD 2 to USD 10 per square foot, which is higher than traditional paints but justified by the long-term benefits. The initial investment in ceramic coatings is offset by the reduced energy costs for heating and cooling, as well as the extended durability of the building materials. When installing ceramic coatings, proper surface preparation is essential for adhesion and longevity. This may involve cleaning, repairing any damage, and applying a suitable primer. The application process should follow the manufacturer’s guidelines to achieve uniform coverage and the desired thickness. Environmental conditions during application, such as temperature and humidity, can also affect the performance of ceramic coatings. Therefore, it is important to apply these coatings under appropriate conditions to ensure proper curing and bonding. Ceramic coatings pose significant challenges in terms of recyclability. Once applied, these coatings form a hard, durable layer that is strongly bonded to the substrate, making separation and recovery difficult. The high-temperature processes required to produce ceramic coatings further complicate recycling efforts, as they cannot be easily melted down or reprocessed like some other materials. As a result, ceramic coatings are typically not recyclable, and most end up in landfills after removal during building renovations.

Table 7. Challenges and considerations that are important for coating systems.

Consideration	Description	Requirements	Installation Difficulty	Advantages	Disadvantages	Impact on Building
Surface Preparation	Ensuring the surface is clean, repaired, and primed	Cleaning, repairing, priming	Moderate	Ensures proper adhesion and longevity	Time-consuming and labor-intensive	Improved durability and performance
Application Process	Following guidelines for even coverage and thickness	Adhering to manufacturer’s instructions	High	Achieves desired performance and uniformity	Requires skilled labor and precision	Enhanced thermal and protective properties
Environmental Conditions	Applying coatings under suitable temperature and humidity conditions	Monitoring temperature and humidity	High	Ensures optimal curing and effectiveness	May limit application windows	Optimal coating performance
Material Compatibility	Ensuring compatibility with existing materials	Checking material compatibility	Moderate	Prevents material degradation and failure	Requires thorough assessment	Extended lifespan of building materials
Long-Term Maintenance	Regular inspections and upkeep to maintain performance	Scheduled maintenance and inspections	Low	Maintains efficiency and durability	Adds to maintenance workload	Sustained energy efficiency and protection
Cost–Benefit Analysis	Evaluating the initial cost against long-term savings	Detailed financial assessment	Moderate	Informs investment decisions	Initial high cost	Informed cost-effective choices

summarizes the challenges and considerations that are important for coating systems.

5. Advanced Glazing Systems

Advanced glazing systems are critical components in modern building design, aimed at improving energy efficiency, thermal comfort, and overall environmental sustainability [89]. These systems are designed to enhance the performance of windows and façades, reducing heat transfer, and improving insulation while allowing natural light to enter the building. By leveraging advanced technologies, these glazing systems contribute significantly to reducing energy consumption for heating and cooling, thereby lowering utility costs and greenhouse gas emissions. One of the primary benefits of advanced glazing systems is their ability to minimize heat loss during winter and reduce heat gain during summer. This dual functionality ensures that buildings remain thermally comfortable year-round, which is particularly important in regions with extreme temperatures [90]. Moreover, advanced glazing systems can improve acoustic insulation, reducing noise pollution from external sources and enhancing indoor comfort. Advanced glazing systems encompass a variety of technologies, each offering unique benefits.

5.1. Applications of Advanced Glazing Systems in Construction Materials

This section explores the various applications of each system offering unique advantages and applications in modern construction.

Table 8. Types of glazing glass applications.

Glazing Type	Subsection	Material Composition	Replaces	Properties	U-Value	Benefits	Challenges
Double-Glazed Windows	Glazed Windows	Two panes of glass with air or inert gas filling	Single-pane windows	Improves insulation, reduces heat transfer	1.2–3.7 W/m2K	Reduces heating/cooling costs, improves comfort	Proper sealing and alignment needed
Triple-Glazed Windows	Glazed Windows	Three panes of glass with two air or inert gas fillings	Single-pane and double-glazed windows	Superior insulation, further reduces heat transfer	0.8–1.6 W/m2K	Maximizes energy efficiency, best for extreme climates	Higher initial cost, thicker units
Low-E Glass	Low-E Glass	Glass with a low-emissivity coating	Traditional clear glass	Reflects infrared light, reduces heat transfer	0.25–1.1 W/m2K	Improves energy efficiency, reduces UV damage	Higher initial cost, specific placement needed
Electrochromic Smart Glass	Smart Glass	Glass with electrochromic layers	Traditional glass and shading devices	Changes tint with electric current	0.25–1.1 W/m2K	Dynamic control over light/heat, improves comfort	Requires electrical integration, higher cost
Photochromic Smart Glass	Smart Glass	Glass with light-sensitive molecules	Traditional glass and shading devices	Darkens in response to sunlight	0.4–1.0 W/m2K	Automatically adjusts to light conditions	No power needed, limited to sunlight changes
Thermochromic Smart Glass	Smart Glass	Glass with thermochromic materials	Traditional glass and shading devices	Becomes opaque with temperature changes	0.5–1.2 W/m2K	Automatic thermal regulation, reduces cooling load	Automatic, no power needed, influenced by temperature

summarizes the different types of glazing glass applications discussed in this study.

5.1.1. Glazed Windows

These windows are constructed with multiple layers of glass, separated by air or gas-filled spaces that act as insulators to reduce heat transfer [91]. The two primary types of glazed windows are double-glazed and triple-glazed windows, each offering distinct advantages in terms of insulation and energy savings. Figure 19 shows the difference between the glazed glasses.

Double-glazed windows consist of two panes of glass with a space between them, which is typically filled with air or an inert gas such as argon or krypton [92]. This space acts as an insulating barrier, reducing the amount of heat that escapes during the winter and the amount of heat that enters during the summer. The glass panes are usually 4 mm thick, and the spacer between them ranges from 6 mm to 20 mm, with the overall unit thickness varying accordingly. Double-glazed windows are highly effective at reducing heat transfer, with U-values (a measure of thermal transmittance) typically ranging from 1.2 to 3.7 W/m²K, depending on the specific materials and gasses used.

Triple-glazed windows, consist of three panes of glass, with two insulating spaces in between [93]. These windows offer even greater thermal performance compared to double-glazed units, with U-values often ranging from 0.8 to 1.6 W/m²K. The additional pane of glass and extra insulating space further reduce heat transfer, making triple-glazed windows ideal for regions with extreme temperatures or for buildings aiming to achieve the highest levels of energy efficiency. The typical thickness of the glass panes remains around 4 mm, while the spacers are similar in size to those used in double-glazed windows, resulting in a thicker overall unit. The materials used in glazed windows have a special coating to reflect infrared light. This coating helps to keep heat inside the building during winter and outside during summer, further enhancing the energy efficiency of the windows. A systematic review by Michael et al. revealed that high-performance glazing technologies, including multi-layer and smart glazing, are crucial for achieving energy efficiency and occupant comfort in buildings [94]. The double-glazed glass reduced heating/cooling costs by up to 20% while the triple-glazed glass reduced heating/cooling costs by up to 30%.

Double-glazed windows typically range from USD 150 to USD 600 per window, while triple-glazed windows can cost between USD 500 and USD 1000 per window. Glazed windows present moderate recyclability, particularly for their glass components. The glass used in these windows is recyclable and can be processed into new glass products, with recycling rates for glass typically reaching up to 90%. However, the recycling process is complicated by the presence of other materials such as plastic spacers, metal frames (aluminum), and sealants, which need to be separated from the glass. Aluminum frames are highly recyclable, with a recycling rate of up to 95%, but the separation of glass from the frame and other components can make the recycling process more labor-intensive. Additionally, inert gas fillings (argon or krypton) used in energy-efficient glazed windows can further complicate the recycling process. When installing glazed windows, proper installation is crucial to ensure that the windows provide optimal performance. This includes ensuring that the window frames are properly sealed to prevent air leakage and that the glazing units are correctly aligned. The use of high-quality materials and professional installation services can significantly impact the effectiveness of glazed windows.

5.1.2. Low-E Glass

Low-emissivity (Low-E) glass reduces the amount of infrared and ultraviolet light that passes through the glass, without compromising the amount of visible light transmitted [95]. This is achieved through a special microscopically thin, transparent coating applied to the glass, which reflects infrared radiation while allowing natural light to enter. Low-E glass is made by applying a metal or metallic oxide coating to one of the surfaces of the glass pane. This coating is usually applied during the manufacturing process and can be applied in a variety of ways, including pyrolytic (hard coat) or sputtered (soft coat) methods [96]. Hard-coated Low-E glass is more durable and suitable for single-pane applications, while soft-coated Low-E glass provides better performance in terms of U-values and solar heat gain coefficients, making it ideal for double- or triple-glazed windows. The properties of Low-E glass are defined by its ability to reflect infrared light, which helps to keep heat inside the building during winter and outside during summer. Low-E glass has a low U-value, typically ranging from 0.25 to 1.1 W/m²K, indicating excellent insulation properties. It also has a low solar heat gain coefficient (SHGC), which measures how much solar radiation is admitted through the glass, thereby reducing cooling loads.

The benefits of using Low-E glass include improved energy efficiency, reduced heating and cooling costs, enhanced thermal comfort, and protection from UV rays, which can cause the fading of furnishings and finishes [97]. Generally, Low-E glass is more expensive than traditional clear glass, with costs ranging from USD 10 to USD 20 per square foot. A study by Michael et al. focused on the thermal and energy performance of advanced glazing systems in different climatic zones [94]. The research found that integrating advanced glazing materials, such as nanogel-filled panels and thermochromic coatings, can significantly reduce cooling loads and improve indoor thermal comfort. For instance, the use of thermochromic glazing, which changes opacity based on temperature, was shown to reduce cooling energy consumption by up to 30% compared to traditional glazing systems. It also reduced UV damage by up to 50%.

Low-E glass is moderately recyclable, with the glass component itself being highly recyclable, typically achieving recycling rates of up to 90%. However, the presence of the thin metallic Low-E coating, which is applied to enhance thermal performance by reflecting heat, complicates the recycling process. The coating must be removed or treated during recycling, which can increase processing time and costs. When installing Low-E glass, the proper orientation and placement of the windows are crucial to maximize the benefits of Low-E glass. Windows facing south or west can significantly reduce cooling loads in summer, while those facing north can help retain heat in winter. Ensuring proper sealing and insulation around the window frames is also essential to prevent air leakage and maintain the insulating properties of the glass.

5.1.3. Smart Glass

Smart glass controls the amount of light and heat that passes through the glass by changing the opacity of the glass in response to external stimuli such as electric currents, light, or heat, as shown in Figure 20 [98]. The primary types of smart glass include electrochromic, photochromic, and thermochromic glass, each offering unique mechanisms for modulating light and heat transmission.

Electrochromic smart glass changes its tint when an electric current is applied, allowing it to switch from clear to opaque or tinted states. This type of smart glass is made by layering materials such as tungsten oxide on the glass surface. When a small voltage is applied, ions move between layers, changing the glass’s optical properties [100]. The typical dimensions of electrochromic glass panels are like standard window sizes, ranging from small panes to large sheets up to several meters in length. The efficiency of electrochromic glass is characterized by its ability to reduce solar heat gain by up to 60% and decrease glare, leading to improved thermal comfort and reduced reliance on HVAC systems. Photochromic smart glass darkens in response to sunlight, like transition lenses in eyeglasses. This type of glass contains light-sensitive molecules that change their structure when exposed to UV radiation, reducing light transmission and heat gain. Photochromic glass is commonly used in windows and skylights to automatically adjust to changing light conditions, enhancing occupant comfort without the need for manual controls or electrical power. Thermochromic smart glass changes its properties based on temperature. This type of glass is coated with a thermochromic material that becomes opaquer as temperatures rise, thus reducing heat gain. Thermochromic glass is particularly effective in regions with high temperature variations, providing automatic thermal regulation that helps maintain comfortable indoor temperatures and reduces cooling loads [101]. A comprehensive review of smart glazing technologies by Liu et al. demonstrated their effectiveness in dynamically controlling solar heat gain and visible light transmission [102]. Electrochromic glazing was found to reduce solar heat gain by up to 60%, leading to lower cooling energy demands and enhanced indoor comfort. Similarly, photochromic and thermochromic glazing technologies, which respond to light intensity and temperature, respectively, provided significant energy savings and improved occupant comfort by automatically adjusting to environmental conditions

Electrochromic glass, for example, can cost between USD 50 and USD 150 per square foot, while photochromic and thermochromic glasses are generally less expensive, ranging from USD 30 to USD 100 per square foot. Smart glass presents significant challenges in terms of recyclability. While the glass component itself is recyclable, the integration of complex technologies such as electrically conductive coatings, embedded electronics, and multi-layer structures makes separation difficult. The electronic components and coatings used in smart glass often hinder the recycling process, as they require specialized facilities for disassembly and treatment. The recyclability of smart glass is further complicated by the use of materials like indium tin oxide in electrochromic glass, which is difficult to recover. As a result, smart glass is typically not recycled in conventional glass recycling processes, and most of it ends up in landfills at the end of its lifecycle.

When installing smart glass, electrical wiring and control systems need to be integrated into the building design to manage the tinting process. Ensuring proper insulation and sealing around the smart glass panels is crucial to maintain their thermal efficiency and prevent air leakage. Additionally, considerations for power supply and maintenance must be addressed to ensure the long-term functionality of the electrochromic systems.

Table 9. Challenges and considerations that are important for glazing systems.

Consideration	Description	Requirements	Installation Difficulty	Advantages	Disadvantages	Impact on Building
Orientation and Placement	Optimal positioning for maximum efficiency	Proper alignment with sun exposure	Moderate	Maximizes energy efficiency	Requires careful planning	Improved thermal comfort and efficiency
Electrical Integration	Necessary for electrochromic glass	Integration with building’s electrical system	High	Allows dynamic control of light/heat	Increases complexity and cost	Enhanced control and comfort
Insulation and Sealing	Ensuring proper sealing for efficiency	High-quality materials and installation	High	Prevents air leakage, maximizes insulation	Requires skilled labor	Optimal performance and energy savings
Material Compatibility	Compatibility with existing structures	Assessment of building materials	Moderate	Ensures durability and effectiveness	Needs thorough evaluation	Extended lifespan of glazing systems
Long-Term Maintenance	Regular checks for functionality	Scheduled maintenance	Low	Maintains performance over time	Adds maintenance workload	Sustained energy efficiency
Cost–Benefit Analysis	Evaluating initial cost vs. long-term savings	Detailed financial assessment	Moderate	Informs investment decisions	High initial investment	Cost-effective energy management

summarizes the challenges and considerations that are important for glazing systems.

6. Phase-Change Materials (PCMs)

PCMs have the unique ability to absorb, store, and release large amounts of latent heat during phase transitions, typically from solid to liquid and vice versa [103]. This property makes them highly effective in regulating indoor temperatures and reducing the need for heating and cooling systems. PCMs can be categorized into two main types: microencapsulated PCMs and PCM-enhanced building materials. Microencapsulated PCMs consist of PCM particles enclosed within a protective shell, which can be integrated into building materials such as concrete, gypsum, or plasterboard. These microcapsules typically range in size from a few micrometers to several millimeters. The encapsulation process helps to prevent the leakage of PCMs and allows for their incorporation into various construction materials without compromising structural integrity.

PCM-enhanced building materials involve the direct incorporation of PCMs into traditional building materials, enhancing their thermal storage capabilities. These materials can include PCM-embedded concrete, wallboards, and insulation panels [104]. The integration of PCMs into building materials allows for a more efficient and seamless way to utilize the thermal storage properties of PCMs in construction. Paraffin-based PCMs have a latent heat storage capacity of about 200 kJ/kg and transition temperatures ranging from 18 °C to 28 °C, making them suitable for building applications. A study by Kurdi et al. highlighted the effectiveness of PCMs as thermal masses in building walls, showing significant potential to reduce heating and cooling costs [105]. The study focused on the integration of paraffin wax, fatty acids, hydrated salts, and butyl stearate into building walls. It found that these materials could absorb and retard heat loss, maintaining indoor comfort and reducing energy consumption by 25%. The incorporation of PCMs in concrete admixtures was identified as the most economical method, although encapsulation techniques are essential to prevent PCM leakage. The efficiency of PCMs in regulating indoor temperatures can lead to significant energy savings by reducing the demand for heating and cooling systems. Another study by Frigione et al. examined the use of PCMs in mortars and concrete, emphasizing their ability to reduce temperature fluctuations and improve thermal comfort in buildings [106]. The review identified that PCMs could reduce the energy required for heating and cooling, especially in extreme climates. The study highlighted the potential of PCMs to achieve energy savings of up to 30% by absorbing and releasing thermal energy during phase transitions. A further study by Frigione et al. demonstrated the benefits of PCMs in maintaining optimal indoor temperatures [106]. It found that incorporating PCMs into building envelopes can significantly reduce temperature variations, leading to improved occupant comfort and lower energy consumption. This study underlined the importance of selecting PCMs with appropriate melting temperatures that align with human comfort levels, typically between 22 °C and 26 °C.

PCMs can help to stabilize indoor temperatures, reducing temperature fluctuations and creating a more comfortable living environment [105,107]. However, one of the main challenges in integrating PCMs is the encapsulation process, which is essential to prevent leakage during phase transitions. Proper encapsulation ensures the long-term durability and efficiency of PCMs, but it increases material costs and complexity. Long-term durability is another concern, as repeated phase transitions can lead to material fatigue, reducing the efficiency of PCMs over time. Solutions such as microencapsulation can mitigate this issue, but further research is needed to enhance the longevity of PCM applications in buildings. When integrating PCMs, practical considerations include selecting materials with appropriate melting points based on the building’s location and climate. Ensuring the adequate encapsulation of the PCMs is essential to maintain thermal performance and prevent leaks over time. The cost of microencapsulated PCMs can range from USD 20 to USD 40 per kilogram, while PCM-enhanced building materials can cost between USD 50 and USD 100 per square meter.

Organic PCMs like paraffin are not easily recyclable due to their chemical structure and degradation over time. Inorganic PCMs, such as salt hydrates, may offer better recyclability potential, but current recycling processes for PCMs are not widely established. Furthermore, the integration of PCMs into building components makes it difficult to separate them for reuse or recycling. Currently, most PCMs are disposed of at the end of their lifecycle, with limited recycling infrastructure in place. However, research is ongoing to improve the recyclability and sustainability of PCMs by developing more eco-friendly formulations and recovery processes.

Table 10. Types of PCM applications.

CM Type	Subsection	Material Composition	Replaces	Properties	Efficiency	Benefits	Challenges or Other Information
Microencapsulated PCMs	Phase-Change Materials	PCM particles enclosed within a protective shell	Standard building materials	High latent heat storage capacity, phase transition at specific temperatures	Reduces energy consumption by up to 30%	Improves thermal comfort, prevents PCM leakage	Higher initial cost, requires proper encapsulation
PCM-Enhanced Building Materials	Phase-Change Materials	PCMs integrated into traditional building materials like concrete, gypsum, or plasterboard	Standard building materials	Enhanced thermal storage capabilities, phase transition at specific temperatures	Reduces energy consumption by up to 30%	Seamless integration, improves thermal comfort	Higher initial cost, needs compatibility with building materials

summarizes the different types of PCM applications.

When installing PCMs, the proper placement and distribution of PCMs are crucial to maximize their effectiveness. PCMs should be positioned in areas with significant temperature fluctuations to fully utilize their thermal storage capabilities. Additionally, the compatibility of PCMs with other building materials must be ensured to prevent any adverse chemical reactions or structural issues. The installation process should follow the manufacturer’s guidelines to achieve optimal performance and longevity.

Table 11. Challenges and considerations that are important for PCM systems.

Consideration	Description	Requirements	Installation Difficulty	Advantages	Disadvantages	Impact on Building
Placement and Distribution	Optimal positioning for maximum effectiveness	Areas with significant temperature fluctuations	Moderate	Maximizes thermal storage capabilities	Requires careful planning	Improved thermal comfort and energy efficiency
Material Compatibility	Ensuring PCMs do not react adversely with other materials	Assessment of building materials for compatibility	Moderate	Prevents adverse chemical reactions	Needs thorough evaluation	Extended lifespan of materials
Installation Process	Following manufacturer’s guidelines for proper installation	Adhering to specific installation protocols	High	Ensures optimal performance and longevity	Requires skilled labor	Optimal thermal performance
Cost–Benefit Analysis	Evaluating the initial cost against long-term energy savings	Detailed financial assessment	Moderate	Informs investment decisions	Higher initial investment	Cost-effective energy management

summarizes the challenges and considerations that are important for PCM systems.

7. Green Roofs and Walls

Green roofs and walls are sustainable building practices that integrate vegetation into the architecture of buildings, providing environmental, economic, and social benefits. They consist of layers that support plant growth and are designed to improve building performance by enhancing thermal insulation, managing stormwater, reducing urban heat island effects, and improving air quality [108]. Figure 21 shows green roofs and walls in buildings.

Extensive green roofs are lightweight systems with a shallow substrate layer (typically 6–20 cm) that supports drought-tolerant and low-maintenance vegetation such as sedums, grasses, and herbs. These roofs are designed for minimal maintenance and irrigation, making them suitable for large roof areas where accessibility is limited [109]. The weight of extensive green roofs ranges from 60 to 150 kg/m², and they typically do not require additional structural support. Extensive green roofs provide thermal insulation, reduce stormwater runoff by absorbing rainwater, and mitigate urban heat island effects by cooling the air through evapotranspiration. The efficiency of extensive green roofs in terms of vegetation depends largely on the plant species used, as drought-tolerant species like sedums require less maintenance and have lower water needs, reducing operational costs. However, the trade-off is that these species may offer less esthetic appeal compared to more diverse planting schemes. Additionally, the thin substrate layer limits their stormwater retention capacity compared to intensive systems.

Intensive green roofs, also known as roof gardens, have a deeper substrate layer (20 cm or more) that can support a diverse range of plants, including shrubs, trees, and lawns. These roofs require more maintenance, irrigation, and structural support due to their increased weight, which can range from 180 to 500 kg/m². The deeper substrate and diverse vegetation in intensive systems provide higher stormwater retention and better thermal insulation, making them more functional in terms of energy savings and biodiversity support. However, these benefits come at the cost of increased operational expenses and maintenance requirements, such as irrigation, weeding, and plant care. Intensive green roofs offer greater esthetic and recreational benefits compared to extensive roofs and can provide significant environmental benefits such as enhanced biodiversity, improved thermal insulation, and a greater stormwater management capacity.

Table 12. Types of green roof and wall applications.

Type	Material Composition	Replaces	Properties	Efficiency	Benefits	Challenges
Extensive Green Roofs	Shallow substrate layer (6–20 cm), drought-tolerant plants	Traditional roofing materials	Lightweight, minimal maintenance	Reduces heat transfer, absorbs rainwater	Thermal insulation, stormwater management, urban heat island mitigation	Requires proper plant selection, structural assessment
Intensive Green Roofs	Deeper substrate layer (20 cm+), diverse plant species including shrubs and trees	Traditional roofing materials	Heavier, requires more maintenance and structural support	Provides significant insulation, higher stormwater retention	Enhanced biodiversity, recreational space, thermal and stormwater benefits	Higher cost, requires irrigation and regular maintenance
Green Façades	Climbing plants supported by trellis or mesh	Traditional façades	Vertical growth, uses climbing plants	Improves thermal performance, air quality	Air quality improvement, noise reduction	Needs structural support, suitable plant selection
Living Walls	Modular panels with plants growing in a substrate	Traditional façades	Integrated system with substrate and plants	Enhances thermal insulation, air quality	Air quality improvement, noise reduction, esthetic enhancement	Complex installation, regular maintenance required

summarizes the different types of green roof and wall applications.

Green walls can be classified into two main types: green façades and living walls [111]. Green façades use climbing plants that grow up and across a building’s exterior, either directly on the wall or supported by a trellis or mesh. Living walls, on the other hand, involve modular panels or systems where plants grow in a substrate supported by the wall structure. Modular living walls with a well-managed irrigation system can support a wider range of plant species and offer better air quality improvements, while green façades are more limited in plant diversity but require less maintenance. They also help to reduce noise pollution and protect the building façade from weathering. In addition to their esthetic and functional benefits, green roofs and walls promote biodiversity by creating habitats for various plant and animal species, which is crucial in urban environments where natural habitats are limited. A comprehensive review by Mayrand et al. highlighted the environmental benefits of green roofs and walls, emphasizing their role in enhancing urban biodiversity and connectivity [112]. The study found that green roofs and walls contribute to urban biodiversity by providing habitats for various species, thereby improving ecological connectivity in urban areas. This biodiversity not only enhances ecological connectivity but also supports pollinators like bees and birds, contributing to local ecosystems. The materials used in green roofs and walls include waterproof membranes, root barriers, drainage layers, filter fabrics, growing substrates, and plant materials. These components work together to support plant growth while protecting the building structure.

Green roofs and walls mitigate urban heat island effects by cooling the surrounding air through evapotranspiration. They also improve air quality by filtering pollutants such as particulate matter (PM10) and carbon dioxide and producing oxygen. This air-purifying effect can have a measurable impact on reducing smog and improving public health in urban areas [113]. Another study focused on the thermal performance of green roofs, demonstrating that they significantly reduce indoor temperatures and energy consumption for cooling [112]. The research indicated that green roofs could lower indoor temperatures by up to 6 °C during the summer, leading to substantial energy savings. Additionally, the study found that green roofs improve stormwater management by retaining up to 70% of rainfall, reducing the risk of urban flooding. A simulation study examined the benefits of green roofs and walls in warm and humid climates [109,112]. The findings revealed that these green technologies effectively reduce heat transfer and enhance the thermal performance of buildings. The study highlighted that green roofs and walls could decrease energy consumption for cooling by up to 25%, making them a viable solution for improving energy efficiency in buildings

Extensive green roofs typically cost between USD 100 to USD 200 per square meter, while intensive green roofs can range from USD 300 to USD 500 per square meter. Green walls generally cost between USD 500 to USD 1500 per square meter, depending on the complexity of the system. They offer partial recyclability, with organic components like plants and soil being fully biodegradable or reusable in landscaping. However, the non-organic components, such as waterproof membranes and drainage layers, pose recyclability challenges. These synthetic materials, typically made from PVC or rubber, are not easily recyclable and often end up in landfills. Efforts are being made to use more sustainable, recyclable materials in the construction of green roof systems, but the overall recyclability remains limited due to the difficulty in separating the components.

When installing green roofs and walls, several design and technical considerations must be considered. These include the structural capacity of the building to support the additional weight, the selection of appropriate plant species for the local climate, and the integration of irrigation and drainage systems to ensure plant health. Proper maintenance is also essential to ensure the long-term performance and benefits of green roofs and walls. This includes regular watering, fertilization, and weeding, as well as periodic inspections to address any issues related to plant health or structural integrity.

Table 13. Challenges and considerations important for green roof and wall systems.

Consideration	Description	Requirements	Installation Difficulty	Advantages	Disadvantages	Impact on Building
Structural Capacity	Ensuring the building can support the additional weight	Structural assessment, additional support if needed	High	Ensures safety and longevity	Higher initial construction cost	Improved structural integrity, extended lifespan
Plant Selection	Choosing appropriate plants for local climate	Knowledge of local climate and plant needs	Moderate	Maximizes plant health and performance	May require expert knowledge	Enhanced esthetic and environmental benefits
Irrigation System	Integrating irrigation to maintain plant health	Design and installation of irrigation systems	High	Maintains plant health, ensures system efficiency	Increases installation complexity and cost	Optimal plant health and system functionality
Maintenance	Regular upkeep to ensure long-term performance	Regular watering, fertilization, weeding	Moderate	Sustains performance and benefits over time	Requires ongoing labor and costs	Consistent performance and benefits
Cost–Benefit Analysis	Evaluating initial costs vs. long-term benefits	Detailed financial assessment	Moderate	Informs investment decisions	Higher initial investment	Long-term cost savings and efficiency

summarizes the challenges and considerations important for green roof and wall systems.

8. Conclusions

This study comprehensively reviewed advanced materials and technologies for enhancing building energy efficiency, sustainability, and occupant comfort. Through detailed analysis, the study highlighted the benefits of BIPVs, advanced insulating materials, coatings, glazing systems, PCMs, and green roofs and walls. BIPVs demonstrated significant potential in integrating renewable energy generation into building structures, offering esthetic, space-efficient, and energy-saving solutions. Advanced insulating materials, such as aerogels, VIPs, and foam insulations, were found to drastically reduce heat transfer and improve thermal performance. Reflective, thermal barrier, and ceramic coatings provided enhanced thermal resistance, durability, and energy efficiency. Glazing systems, including double- and triple-glazed windows, Low-E glass, and smart glass technologies, showcased their effectiveness in reducing heat gain, improving insulation, and providing dynamic control over light and heat transmission. PCMs, with their ability to store and release latent heat, were identified as effective in stabilizing indoor temperatures and reducing energy consumption. Green roofs and walls contributed to urban biodiversity, thermal insulation, stormwater management, and air quality improvement. In answering the research question, the review concludes that integrating advanced materials such as BIPVs, PCMs, and high-performance insulations significantly reduces energy consumption in buildings. The data collected from various studies demonstrated that energy savings can range between 20% and 50%, depending on the materials and technologies applied. Additionally, environmental impacts were reduced through lower greenhouse gas emissions, validating the hypothesis that these technologies make modern buildings more energy-efficient and sustainable. The study underscores the importance of continued research and development in advanced building materials to further optimize their performance and broaden their applications in sustainable construction.