Search Results (31)

The construction sector presently consumes about 40% of global energy and generates 36% of CO₂ emissions, making facade retrofits a priority for decarbonising buildings. This review clarifies how ventilated facades (VFs), wall assemblies that interpose a ventilated air cavity between outer cladding and the insulated structure, address that challenge. First, the paper categorises VFs by structural configuration, ventilation strategy and functional control into four principal families: double-skin, rainscreen, hybrid/adaptive and active–passive systems, with further extensions such as BIPV, PCM and green-wall integrations that couple energy generation or storage with envelope performance. Heat-transfer analysis shows that the cavity interrupts conductive paths, promotes buoyancy- or wind-driven convection, and curtails radiative exchange. Key design parameters, including cavity depth, vent-area ratio, airflow velocity and surface emissivity, govern this balance, while hybrid ventilation offers the most excellent peak-load mitigation with modest energy input. A synthesis of simulation and field studies indicates that properly detailed VFs reduce envelope cooling loads by 20–55% across diverse climates and cut winter heating demand by 10–20% when vents are seasonally managed or coupled with heat-recovery devices. These thermal benefits translate into steadier interior surface temperatures, lower radiant asymmetry and fewer drafts, thereby expanding the hours occupants remain within comfort bands without mechanical conditioning. Climate-responsive guidance emerges in tropical and arid regions, favouring highly ventilated, low-absorptance cladding; temperate and continental zones gain from adaptive vents, movable insulation or PCM layers; multi-skin adaptive facades promise balanced year-round savings by re-configuring in real time. Overall, the review demonstrates that VFs constitute a versatile, passive-plus platform for low-carbon buildings, simultaneously enhancing energy efficiency, durability and indoor comfort. Future advances in smart controls, bio-based materials and integrated energy-recovery systems are poised to unlock further performance gains and accelerate the sector’s transition to net-zero. Emerging multifunctional materials such as phase-change composites, nanostructured coatings, and perovskite-integrated systems also show promise in enhancing facade adaptability and energy responsiveness. Full article

With the increasing demand for energy-efficient and sustainable building materials, innovative cooling technologies have become a key focus in the construction industry. This study developed a double-layer cooling coating integrating evaporation and radiation mechanisms. The first layer consists of a TiO₂/PUA radiation layer, where rutile TiO₂ is incorporated into polyurethane acrylate (PUA) resin to enhance solar reflectivity. The second layer is a P(NVP-co-NMA) hydrogel, which evaporates water at high temperatures and absorbs moisture from the air at low temperatures, eliminating the need for additional water supply systems. The TiO₂/PUA@P(NVP-co-NMA) coating demonstrates high solar reflectivity and infrared emissivity, effectively reducing indoor temperatures by dissipating heat through water evaporation and radiative cooling. Testing showed a temperature reduction of approximately 7.6 °C in a small house with this coating under simulated conditions. This material demonstrates favorable properties that may make it suitable for applications on building roofs and exterior walls, potentially addressing some limitations of conventional evaporative or radiative cooling systems. Its observed multi-effect cooling performance indicates promise for contributing to energy savings in sustainable building designs. Full article

This research develops a numerical fire model for a converter transformer utilizing the Fire Dynamics Simulator (FDS). The model’s accuracy was validated through comprehensive evaluations of temperature distribution, radiative heat transfer, and mass burning rate. Additionally, the cooling efficacy of fire-resistant coating and fine water mist with varying droplet sizes was investigated. The results indicate that fireproof coating significantly reduces the surface temperature of the transformer, thereby enhancing its fire resistance. Specifically, temperature reductions of 57.68%, 45.63%, 37.78%, and 36.78% were recorded at different facade heights. Furthermore, the cooling performance of fine water mist is strongly influenced by droplet size, primarily due to thermal buoyancy effects. Larger droplets (400 μm) exhibited the most efficient cooling effect directly beneath the spray, achieving temperature reductions of up to 67%. In contrast, smaller droplets (100 μm) showed diminished cooling performance in certain regions, owing to the compensatory buoyancy of hot air, even resulting in an 11% temperature increase in some cases. During the flame stabilization phase, the mass burning rate stabilized between 0.056 kg/(m²·s) and 0.070 kg/(m²·s), with the inhibitory effect of small particle mist becoming pronounced only after 450 s. These findings offer critical insights for optimizing fire protection strategies for converter transformers, highlighting the significance of cooling mechanisms and material properties. Full article

Radiative cooling, an emerging technology that reflects sunlight and emits radiation into outer space, has gained much attention due to its energy-efficient nature and broad applicability in buildings, photovoltaic cells, and vehicles. This study focused on fabricating SiO₂-polymethyl methacrylate (PMMA) and TiO₂-SiO₂-PMMA thick films via the blade-coating method. The investigation aimed to improve cooling performance by adding TiO₂ particles to increase the coverage area and utilize the TiO₂ reflectance ability. The characterizations of the emissivity/absorptivity, solar reflectance, and microstructure of the thick films were conducted by using ultraviolet–visible/near-infrared (UV-Vis/NIR) diffuse reflection spectroscopy and scanning electron microscopy, respectively. Experimental results revealed that the maximum temperature drops of approximately 9.4 and 9.8 °C were achieved during the daytime period for SiO₂-PMMA and TiO₂-SiO₂-PMMA thick films. The total solar radiation reflectivity increased from 71.7 to 75.6% for SiO₂-PMMA radiative cooling thick films after adding TiO₂. These findings underscored the potential of TiO₂-SiO₂-PMMA thick films in advancing radiative cooling technology and cooling capabilities across various applications. Full article

Due to climate change, population increase, and the urban heat island effect (UHI), the demand for cooling energy, especially in urban areas, has increased and will further increase in the future. Technologies such as radiative cooling offer a sustainable and energy-free solution by using the wavelength ranges of the atmosphere that are transparent to electromagnetic radiation, the so-called atmospheric window (8–13 µm), to emit thermal radiation into the colder (3 K) outer space. Previous publications in the field of textile building cooling have focused on specific fiber structures and textile substrate materials as well as complex multi-layer constructions, which restrict the use for highly scaled outdoor applications. This paper describes the development of a novel substrate-independent coating with spectrally selective radiative properties. By adapting the coating parameters and combining low-emitting and solar-reflective particles, along with a matrix material emitting strongly in the mid-infrared range (MIR), substrate-independent cooling below ambient temperature is achieved. Moreover, the coating is designed to be easily applicable, with a low thickness, to ensure high flexibility and scalability, making it suitable for various applications such as membrane architecture, textile roofs, or tent construction. The results show a median daytime temperature reduction (7 a.m.–7 p.m.) of 2 °C below ambient temperature on a hot summer day. Full article

Passive radiative cooling materials are widely recognized as attractive innovations for reducing emissions and expanding life-saving cooling access. Despite immense research attention, the adoption of such technologies is limited largely due to a lack of scalability and cost compatibility with market needs. While paint and coating-based approaches offer a more sensible solution, many demonstrations suffer from issues such as a low solar reflectance performance or a lack of material sustainability due to the use of harmful solvents. In this work, we demonstrate a passive radiative cooling paint which achieves an extremely high solar reflectance value of 98% using a completely water-based formulation. Material sustainability is promoted by incorporating size-dispersed calcium phosphate biomaterials, which offer broadband solar reflectance, as well as a self-crosslinking water-based binder, providing water resistance and durability without introducing harmful materials. Common industry pigments are integrated within the binder for comparison, illustrating the benefit of finely-tuned particle size distributions for broadband solar reflectance, even in low-refractive-index materials such as calcium phosphates. With scalability, outdoor durability, and eco-friendly materials, this demonstrated paint offers a practical passive radiative cooling approach without exacerbating other environmental issues. Full article

The building envelope serves as a barrier against climatic conditions and as insulation to prevent energy waste within buildings. As global energy shortages become more pressing, the requirements for building envelopes are becoming increasingly stringent. Among the available technologies, phase change materials (PCMs) stand out for their high latent thermal energy storage and temperature stabilization capabilities. This paper reviews the recent advancements in PCM technology for building envelopes, starting with an overview of organic, inorganic, and eutectic PCMs, along with their respective advantages and disadvantages. The paper explores various incorporation methods such as shape stabilization, macroencapsulation, micro/nanoencapsulation, and solid–solid transition techniques. The integration of PCMs enhances thermal inertia, reduces thermal fluctuations, and delays heat peaks, presenting several multifunctional benefits. However, challenges such as fire hazards, potential toxicity, pollution, reduced mechanical performance, and higher initial costs persist. In light of these challenges, criteria for PCM integration in building applications are introduced. Additionally, the paper reviews recent hybrid technologies that combine PCMs with other novel technologies for building envelopes, including radiant temperature regulation systems, thermochromic windows, passive radiative cooling coatings, and others. It is shown that these PCM-integrated hybrid technologies significantly improve energy savings and indoor comfort. PCMs offer substantial potential for modern green building strategies and have further applications in other building contexts. Finally, the paper provides future prospects for studies in this field, aiming towards a green and energy-saving future. Full article

This study focuses on improving human thermal comfort in a high-temperature outdoor environment using vests with a radiative cooling coating. The effects of coating thickness on the radiative cooling performance were first evaluated, and an optimal thickness of 160 μm was achieved. Then, six subjects were recruited to evaluate the thermal comfort in two scenarios: wearing the vest with radiative cooling coatings, and wearing the standard vest. Compared with the standard vest, the coated vest decreases the maximum temperature at the vest inner surface and the outer surface by 5.54 °C and 4.37 °C, respectively. The results show that thermal comfort is improved by wearing radiative cooling vests. With an increase of wet bulb globe temperature (WBGT), the improving effects tend to decline. A significant improvement in human thermal comfort is observed at a WBGT of 26 °C. Specifically, the percentage of thermal sensation vote (TSV) wearing the cooling vest in the range of 0 to 1 increases from 29.2% to 66.7% compared with that of the untreated vest. At the same time, the average value of thermal comfort vote (TCV) increases from −0.5 to 0.2. Full article

This paper proposes a temperature-adaptive radiative cooling (TARC) coating with simple preparation, cost effectiveness, and large-scale application based on a thermochromic powder. To determine the energy efficiency of the proposed TARC coating, the heat transfer on the surface of the TARC coating was analyzed. Then, a typical two-story residential building with a roof area of 258.43 m² was modeled using EnergyPlus. Finally, the energy-saving potential and carbon emission reduction resulting from the application of the proposed TARC roof in buildings under different climates in China were discussed. The results showed that the average solar reflectivity under visible light wavelengths (0.38–0.78 μm) decreases from 0.71 to 0.37 when the TARC coating changes from cooling mode to heating mode. Furthermore, energy consumption can be reduced by approximately 17.8–43.0 MJ/m² and 2.0–32.6 MJ/m² for buildings with TARC roofs compared to those with asphalt shingle roofs and passive daytime radiative cooling (PDRC) roofs, respectively. This also leads to reductions in carbon emissions of 9.4–38.0 kgCO₂/m² and 1.0–28.9 kgCO₂/m² for the buildings located in the selected cities. To enhance building energy efficiency, TARC roofs and PDRC roofs are more suitable for use on buildings located in zones with high heating demands and high cooling demands, respectively. Full article

A passive cooling method with great potential to lower space-cooling costs, counteract the urban heat island effect, and slow down worldwide warming is radiant cooling. The solutions available frequently require complex layered structures, costly products, or a reflective layer of metal to accomplish daytime radiative cooling, which restricts their applications in many avenues. Furthermore, single-layer paints have been used in attempts to accomplish passive daytime radiative cooling, but these usually require a compact coating or only exhibit limited cooling in daytime. In our study, we investigated and evaluated in daytime the surrounding cooling outcome with aid of one layer coating composed of BaSO₄/TiO₂ microparticles in various concentrations implanted in the PVDF-HF polymers on a concrete substrate. The 30% BaSO₄/TiO₂ microparticle in the PVDF-HF coating shows less solar absorbance and excessive emissivity. The value of solar reflectance is improved by employing micro-pores in the structure of PVDF polymers without noticeable effect on thermal emissivity. The 30% BaSO₄/TiO₂/PVDF coating is accountable for the hydrophobicity and proportionate solar reflection in the UV band, resulting in efficient solar reflectivity of about 95.0%, with emissivity of 95.1% and hydrophobicity exhibiting a 117.1° water contact angle. Also, the developed coating could cool to about 5.1 °C and 3.9 °C below the surrounding temperature beneath the average solar irradiance of 900 W/m⁻². Finally, the results demonstrate that the 30% BaSO₄/TiO₂/PVDF-HF microparticle coating illustrates a typical figure of merit of 0.60 and is also capable of delivering outstanding dependability and harmony with the manufacturing process. Full article

Radiative cooling is a promising strategy to address energy challenges arising from global warming. Nevertheless, integrating optimal cooling performance with commercial applications is a considerable challenge. Here, we demonstrate a scalable and straightforward approach for fabricating green radiative cooling coating consisting of methyl cellulose matrix-random diatomites with water as a solvent. Because of the efficient scattering of the porous morphology of diatomite and the inherent absorption properties of both diatomite and cellulose, the aqueous coating exhibits an excellent solar reflectance of 94% in the range of 0.25–2.5 μm and a thermal emissivity of 0.9 in the range of 8–14 µm. During exposure to direct sunlight at noon, the obtained coating achieved a maximum subambient temperature drop of 6.1 °C on sunny days and 2.5 °C on cloudy days. Furthermore, diatomite is a naturally sourced material that requires minimal pre-processing, and our coatings can be prepared free from harmful organic compounds. Combined with cost-effectiveness and environmental friendliness, it offers a viable path for the commercial application of radiative cooling. Full article

This study aims to investigate the heat and thermal insulation mechanisms of aerogel heat-insulating reflective coatings. Two working conditions, the hot box method and the open environment at the hot end, were simulated using a gypsum board as the substrate. We conducted thermal tests on blank panels, composite panels with aerogel heat-insulating reflective coatings, and XPS-insulated composite panels for two operating conditions. And the thermal insulation power calculation was carried out for the reflective and barrier materials. The test results show that the air temperature differences between the hot and cold ends of the blank, aerogel coating, and XPS boards under the hot box method were 28.8 °C, 38.2 °C, and 55.2 °C, respectively, and that the air temperature differences between the cold ends of the coating and XPS panels under the natural environment heating condition were 24.2 °C and 24 °C, respectively. Theoretical calculations show that the aerogel heat-insulating reflective coatings produce a net radiative cooling power of 145.9 W/m² when the surface of the specimen is at the same temperature as the ambient temperature. The heat flux powers of the aerogel coating board and XPS panel were 9.55 W/m² and 1.65 W/m² when the temperature difference between the two surfaces on both sides of the specimen was 10 °C, respectively. Full article

Radiative sky cooling is an appealing form of heat exchange between terrestrial objects and outer space through thermal radiation, which is attracting worldwide interest due to its nature as passive cooling, that is, cooling without consuming energy. Due to a recent breakthrough in material science, sub-ambient daytime radiative sky cooling has been effectively achieved, which has significantly stimulated research interest in this field. In view of the numerous radiative coolers being reported as having excellent spectral properties and cooling ability under sunlight, integrating these superb cooling materials into building skins is a promising route to implementing radiative sky cooling technology. To this end, this study deploys state-of-the-art colored radiative cooling coatings as a new retrofitting strategy for building walls, and then conducts a comprehensive performance evaluation by considering a high-rise building situated in the hot-humid city of Hong Kong. Potential benefits of implementing differently colored cooling wall strategies, including their performance regarding thermal insulation, energy savings, economic viability, and environmental sustainability, were thoroughly investigated. The obtained results elucidate that for the utilization of the porous P(VdF-HFP)-based bilayer wall, relative to the monolayer, the frequency of the wall temperature exceeding the surrounding environment on an annual basis can be further reduced by up to 4.8%, and the yearly savings in cooling electricity vary from 855.6 to 3105.6 kWh (0.4–1.5%) with an average of 1692.4 kWh. Besides this, the yearly savings in net electricity cost vary from 1412.5 to 5127.3 HKD and the reduction in carbon emissions ranges from 1544.4 to 5606.1 kg with an average of 3055.0 kg. In addition, discussions of the combination of the super-cool roof strategy with blue porous polymer-based cooling walls reveal that the achievable savings in terms of energy costs and reductions in carbon emissions are 1.6 and 2.2 times more than either the application of the super-cool roof or porous polymer bilayer walls alone, respectively. This research offers new understandings of the deployment of colored cooling coatings on vertical building façades in hot and humid regions, which can considerably facilitate the realization of low-energy buildings in a passive approach for stakeholders. Full article

Cooling energy consumption is a major contributor to various sectors in hot climates with a significant number of warm days throughout the year. Buildings account for 40% of total energy consumption, with approximately ∼30–40% of that used for cooling in geographical areas such as Iran. Energy demand for cooling is an important factor in the overall energy efficiency of electric mobility. Electric vehicles (EVs) consume ∼30–50% of energy for the air conditioning (AC) system. Therefore, the efficient management of the cooling demand is essential in implementing energy-saving strategies. Passive radiative cooling is capable of providing subambient cooling without consuming any energy. This article reviews potential applications of passive radiative cooling in reducing cooling energy for buildings. It also provides a rough estimate of the amount of energy saved when applying a radiative cool roof to a model building. It is shown that by using radiative cool materials on roofs, the share of electricity usage for cooling can be reduced to 10%, leading to a reduction in cooling load by 90%. Additionally, the potential use of radiative cool coats of various types for different EV components, such as shell/body, windows, and fabrics, is introduced. Although the prospects of the design and engineering of radiative cooling products appear promising for both buildings and EVs, further investigations are necessary to evaluate scalability, durability, and performance based on factors such as geography and meteorology. Full article

Radiation cooling is a passive energy saving cooling technology. The process of cooling heat transfer liquid due to the combined effect of night radiative cooling and convection of air at negative temperatures (in winter) is studied. The radiator used for cooling was built into the roof of the building. Its radiating plate was made of a steel sheet coated with zinc oxide. In it, heat dissipation was carried out both from the upper and lower sides of the radiating plate. The experimental values of the heat flux ranged from 20 to 80 W·m⁻² at a temperature difference between heat transfer liquid and air from 5 to 15 °C and ambient air temperature from −17 to +5 °C. The correctness of the model for calculating the heat flux in winter conditions was confirmed. A theoretical calculation showed that, in winter, the heat flux removed by the radiator will be 15% less than the heat flux in summer. The amount of heat transferred per watt of electrical power of the refrigeration unit reached 8 W·W⁻¹. To keep the refrigeration unit with radiative heat transfer more efficient than in a conventional vapor compression chiller, the heat transfer liquid temperature should be 6 °C above the atmospheric temperature air. The results of the study show that radiative cooling can be used in winter and may be useful for the development of energy-efficient cooling systems for various purposes (air conditioning, industrial cooling systems and fruit storage chambers). Full article