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Study on energy saving effect of heat-reflective insulation coating on envelopes in the hot summer and cold winter zone

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Abstract

To discuss the energy saving effects of heat-reflective insulation coating on exterior envelope walls in the hot summer and cold winter zone, the experimental apparatus and the actual test rooms are built respectively, the heat flux data of east, south and west walls are analyzed by monitoring the wall temperature changes of two test rooms with and without the heat reflective insulation coating in Hangzhou in summer and winter. The experimental results indicate that the heat reflective insulation coating could reduce the exterior wall surface temperature effectively, and the maximum temperature change is about 8–10 °C. By calculating, it was found that the annual air-conditioning electricity saving with heat reflective insulation coating on exterior walls is about 5.8 kWh/(m2 month), which shows that the energy saving effect of the heat insulation coating on the exterior wall is obvious in Hangzhou.

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... They were found to be able to reduce inside and outside wall surface temperature from 4.7 to 20.0°C [3]. In warm and humid climate like Hangzhou, China, it was found that heat reflective insulation coating could reduce outside surface temperature of test boxes by 8.0 to 10.0°C [4]. An experimental house was constructed in Nanchang, Jiangsu, China which is classified as a hot and humid climate area. ...
... The average inside surface temperature difference was 2.5°C. The results also agreed well with the past studies [3][4][5][6][7][8][9][10]. ...
... The energy simulations using the EnergyPlus software provided the similar results to the actual measurements. 4 ...
... Xiao, H. et al. pointed out that air-conditioning systems, household appliances, and lighting systems are the three technologies with the highest potential for carbon reduction in the long term, accounting for 72.9% of the total carbon-reduction potential in the building sector in China [28]. The literature [29,30] points out that heat-reflective insulation coatings on external walls can effectively reduce the surface temperature of external walls in hot-summer and cold-winter regions, with good carbon-reduction benefits. In addition, photovoltaics have excellent carbon-reduction benefits [31,32]. ...
... Xiao, H. et al. pointed out that airconditioning systems, household appliances, and lighting systems are the three technologies with the highest potential for carbon reduction in the long term, accounting for 72.9% of the total carbon-reduction potential in the building sector in China [28]. The literature [29,30] points out that heat-reflective insulation coatings on external walls can effectively reduce the surface temperature of external walls in hot-summer and cold-winter regions, with good carbon-reduction benefits. In addition, photovoltaics have excellent carbon-reduction benefits [31,32]. ...
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With limited investment costs, how to fully utilize the carbon-reduction capacity of a campus in terms of buildings, equipment, and energy is an important issue when realizing the low-carbon retrofit of office parks. To this end, this paper establishes a mathematical optimization model for the decarbonization-based retrofit of existing office parks, based on the genetic algorithm, taking into account the relationship between cost, energy-consumption, and carbon-emissions, and taking the maximum carbon reduction of the park over its whole life as the optimization goal. The validity of the model was verified in conjunction with a case study of an office park in Nanchang, China. The case study shows that, compared with current typical parks, the carbon reduction through an office park’s decarbonization retrofit has a non-linear correlation with the investment cost, and when the total investment cost of the park is above CNY 60 million, the increase in carbon reduction with the increase in the investment cost is gradually weakened, and the park achieves the maximum carbon reduction of 236,087 t when the investment cost reaches CNY 103 million. Under the current technical and economic conditions, the investment-cost–carbon-reduction benefits of different carbon-reduction technologies are different, the carbon-reduction benefit of increasing renewable energy utilization is the best, and the carbon-reduction benefit of upgrading the energy efficiency of the park’s supply-and-use system is lower than that of renewable energy utilization, but better than that of upgrading the performance of the building envelope system. In addition, the configuration of the parameters of the same low-carbon technology in different forms of buildings varies significantly, due to differences in the building form and daily use. The model established in this paper is able to give a comprehensive optimized building–equipment–energy configuration plan for existing office parks, when maximizing carbon reduction under different investment costs, which guides the park’s decarbonization retrofit.
... Experimental findings demonstrate that the heat-reflecting insulation coating can potentially reduce the temperature of the exterior wall surface by about 8-10°C. Based on calculations, applying a heat-reflecting insulation coating on the outside walls results in a substantial energy savings of 5.8 kWh/m 2 /month [15]. Retroreflective materials can reflect solar light back in the direction it came from, which helps to overcome the limitations of highly reflective materials. ...
... In the literature, different studies focus on emergency systems [25][26][27][28][29][30] and underline the needs of this construction type, which requires a rapid construction time schedule. Song [31] highlights that the construction speed increases the required energy, especially for the structures. ...
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... This coating reduces the heat transferred into the room and therefore the cooling load through high shortwave reflectivity (in the wavelength band of 0.3-2.5 μm) over the visible and near-infrared spectrum [5]. Although studies have shown that reflective coatings can effectively reduce building surface temperature, heat accumulation and cooling energy consumption [6][7][8][9], there is still room for improvement. years [40]. ...
... Jian et al. [11,12] calculated the thermal load value of external walls with insulation materials of different thicknesses and determined the law that describes how the thickness of the insulation layer changes with the energy-saving effect. Meanwhile, Tu et al. [13][14][15][16] proposed evaluating the overall thermal performance of residential building envelopes in areas characterized by hot summers and cold winters by using the system evaluation index of the thermal performance of building envelopes, including in terms of the heat transfer and solar radiation coefficients, while Tummu et al. [17,18] conducted experiments related to the cooling load of air conditioners under different window/wall ratios and different building envelopes. Here, the results indicated that when there are no windows, both the internal and the external insulation can reduce the building's energy consumption, while with an increase in window area, the internal insulation can still reduce the energy consumption but the external insulation exhibits an "anti-energy-saving" characteristic. ...
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For a large number of monolithic buildings in the Wenzhou area, serious cold air infiltration occurs at night due to the poor insulation performance of the enclosure structure. This results in the indoor temperature often falling below the thermal comfort zone, which is compounded by high relative humidity. Various types of energy-efficient buildings, considering different envelope structures (exterior walls, roofs, exterior windows, and shading designs), were constructed, taking into account both structural characteristics and residents’ energy consumption habits. The building environment and energy consumption during the transition period (i.e., summer and winter) were analyzed using the ideal solution similarity ranking preference method (TOPSIS) and the building energy simulation software, EnergyPlus 9.5. This analysis aimed to identify four energy-efficient building models closest to the ideal solution. Comparing the indoor environment parameters and load values of the energy-saving buildings with those of the basic building yielded the following results: the average building load of the energy-saving buildings was 79.48 to 122.00 W lower than that of the basic building. The average temperature difference between the exterior walls of the energy-saving buildings and the interior temperature was 0.6 to 1.45 °C lower than that of the basic building. Similarly, the average temperature difference between the exterior windows and the interior temperature of the energy-saving buildings was 0.56 to 0.98 °C lower than that of the basic building. Additionally, the average temperature difference between the roof and room temperature of the energy-saving buildings was 0.54 to 0.39 °C lower than that of the basic building. Furthermore, the average indoor temperature of the energy-saving buildings was 1.50 to 2.11 °C higher than that of the basic building. In addition, when compared with the basic building, the energy-saving buildings could save 5.66 to 16.39 kg of standard coal and reduce CO2 emissions by 1.60 to 4.47 kg during the transition period. The study of the energy-saving envelope structure combination form in Wenzhou provides a reasonable basis for building an energy-saving envelope structure combination form in the tropical monsoon climate area, which is of great significance for reducing building energy consumption.
... According to the correlation analysis in the previous section, there is a strong positive linear correlation between the hourly EC of air conditioning and the change in outdoor ambient temperature. It was also proved in the related literature (Guo et al., 2012) that the heat gain of buildings in summer increased with the increase of outdoor ambient temperature. Considering the linear regression method, the relationship between power consumption and outdoor ambient temperature was analyzed to guide the prediction of future EC. ...
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Cool roofs can reduce building energy consumption and improve indoor and outdoor thermal environments. A phase change material cool roof (PCMC roof) was proposed in order to reduce roof heat gain in the indoor thermal environment in summer. Indoor thermal and energy environmental parameters in three full-size rooms (ordinary room, PCM room, and PCMC room) were tested from July to September 2022. The heat transfer characteristics and energy saving effect of roofs were investigated by combining experimental analysis with numerical analysis. Compared with the ordinary roof, the PCMC roof decreased external and internal roof surface real-time temperatures up to 30.0 !C and 6.4 !C respectively, and reduced the roof inner surface heat flux of 33.3%-66.7%. Compared with the relevant roof studies, the energy saving and cooling effects are more significant. Then, based on the mathematical model of roof heat transfer, the correlation analysis between seven different elements was carried out to evaluate the energy-saving effect of PCMC roof. This study investigates the PCMC roof from the aspects of roof heat transfer characteristics, influence on indoor thermal environment, energy saving evaluation, etc., which provides a more complete and valuable reference for advancing building roofs.
... Heat-reflective asphalt pavement is to coat the road surface with a material with a high reflectivity to the solar radiation energy, inhibiting pavement temperature rise Then the key innovation points to the preparation of heat-reflective coating materials. In fact, the functional coating was first used in the field of building [7]. Researchers have managed to transplant the technology into asphalt pavement. ...
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The performance of ultra-thin wear layer (UTWC) is sensitive to solar radiation and ambient temperature fluctuation. For the purpose of boosting the durability of thermochromic materials in service life as well as improving the function of temperature controlling of asphalt mixtures, a novel pellet was prepared by ion displacement method. The temperature control mechanism for asphalt ultra-thin wear layer with pellets was also investigated. The uniaxial compression experiment and differential scanning calorimetry were deployed to investigate the mechanical strength and phase change characteristics of the pellets. The results indicate that the pellet possesses the merits of high elastic strength and strong sensitivity to ambient temperature. The incorporation of pellets can alleviate thermal fluctuation and improve the high temperature performance of UTWC but reduce its low temperature performance. The specific UTWC with pellets exhibits a maximum temperature reduction of 5.5 • C. The incorporating of pellets in asphalt mixture provides the characteristics of phase change function, alters the thermal properties, thus possess the ability to control temperature of UTWC well.
... The method is recognized and widely used in in situ measurements of thermal properties of partitions of many insulation materials in steady and dynamic conditions-the described case relates to the steady state. The literature widely describes the measurement methodology related to building materials [14][15][16][17][18][19][20][21][22][23] and thin-film insulation materials with reflective properties [24][25][26][27]. The research results obtained by the cited authors justify the credibility of the method. ...
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In this paper, a method to determine the thermal conductivity coefficient λ in a 200 μm thick heat reflective paint layer, filled with polymer nanospheres with a Total Solar Reflectance (TSR) of 86.95%, is proposed and presented. For this purpose, a “hot box”-type (cube-shaped) test rig was built to carry out experimental tests to measure the temperature distribution on the surface of a double-layer wall containing the material under investigation. Together with the experimental studies, a CFD numerical model was prepared to understand the nature of flow and heat transfer inside the cube—the test chamber. Based on the proposed measurement and analysis method, the thermal conductivity coefficient of the heat reflective coating layer was λ = 0.0007941 W/m∙K.
... With the development of technology, high-temperature emission of infrared radiation also increases (Trevisan et al., 2021). To reduce this low emissivity materials are used by different researchers in the form of paints/coatings, polymer, composite, and film by different techniques (Guo et al., 2012). As we know that Low-E materials have great importance in buildings, industries, and aircraft to reduce the effect of absorption from thermal infrared radiations (Shakir et al., 2019). ...
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Recently, low-emissivity paint has gained more importance than commercial paints. Low emissivity (Low-E) Paint also termed as a coating for radiation control, in which the emissivity of radiations of longer waves are reduced dramatically (i.e., the emissivity of commercially available paint is 0.9) by imparting low emissivity particles in the base paint but not suitable to reduce near-infrared radiation. Commercially available paints as of today have minimum of 0.7 emissivity and it does not give any significant energy saving. The low emissivity property of paint makes it particularly suitable for reducing the radiative heat exchange in many domestic applications i.e., home electronics, building construction components, roof surfaces, heat storage tanks, and pipes, etc in result, low power required to heat or cool the building in respective whether conditions. In this work, different samples of white paint were prepared in the lab by using a low shear mixer (mechanical stirrer) under very controlled conditions and studied the results of dry paint films to reduce the thermal emissivity then commercially available paint. Then we investigate the drying time of the wet paint films and analyze thermal heat into visible light through thermal imaging camera, Crosshatch, and IR transmission. We also studied the emissivity through ET-100 and aging stability through a weather-o-meter instrument, which investigated that emissivity value achieved in the range of 0.4-0.6 than commercial paints. The results showed that paint exhibits an acceptable aesthetic emissivity value of ∼0.60. It was calculated theoretically that by the use of this novel Low-E paint, annually about 20%-25% less energy will be consumed in building for cooling or heating.
... Reducing environmental pollution (CO 2 emissions) throughout the life cycle (production, operation, and disposal) of buildings is an urgent and important problem. The European Commission (EC) has identified the building sector as a key enabler in its long-term decarburization strategy by targeting a reduction in CO 2 emissions of at least 80% by the year 2050 [5][6][7]. ...
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Multi-skin ventilated facades with integrated building elements that respond to climatic conditions (mechanized openings and automatic shading with intelligent control) present the potential of improving overall annual energy savings by adapting the thermal properties of buildings. This paper presents a literature review on multi-skin adaptive ventilated facades. Additionally, this article presents a literature review on building envelopes that contain inner-air layers. The operation modes of the air layer used in building enclosure structures are classified and summarized and the thermal performance and benefits of climate-adaptive facades are discussed and reviewed. The existing operation modes of the air layer used in building envelopes are summarized, outlined and roughly classified into the following types: the enclosed type, the naturally ventilated type and the mechanically ventilated type. One of the sustainable development trends is the investigation and application of energy-efficient climate-adaptive facades. In this study, the energy modeling of a high-rise office building was calculated using the Green Building Studio. The annual energy, the annual CO2 emissions, and life cycle energy for the following three types of facade were estimated: a single-layer facade made of three-layer glass with argon, a double ventilated facade, and a triple ventilated facade with a double chamber. The calculation results show that the annual energy of the building with an adaptive triple-skin facade could be reduced by 15% compared with buildings with a single skin facade.
... Applying low-emissivity materials to the building envelope has been shown to be a promising strategy 19,20 . Metalized and metal films or foils (laminated with other materials) 21,22 and low-emissivity paints containing heat-reflective aluminium (Al) or silver dust as radiant barriers have been proposed to be installed with sufficient air layers, usually within the building envelopes 23 . ...
Article
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B uildings are important users of energy in present-day society, and energy-efficient buildings play an increasingly important role in sustainability 1. More than 76% of total electricity and 40% of all energy in the United States are consumed to provide comfortable, well-lit and well-conditioned buildings 2 , which results in a cost of more than $430 billion annually and substantial global greenhouse gas emission 3,4. The heating, ventilation and airconditioning (HVAC) systems of buildings contribute to about 40% of the building energy consumption, which is directly related to the heating and cooling demands of buildings 5. This huge energy consumption is causing severe environmental and economic problems. It is therefore essential to develop innovations of science and technology to achieve improved energy efficiency of building HVAC with a reduced carbon footprint. In addition to building insulation materials with low thermal conductivity such as expanded polystyrene, vacuum insulation panels and aerogels 6 , engineering the radiative properties of building envelopes is emerging as a promising approach for building energy savings. For instance, near-infrared (NIR) reflective cooling coatings have been developed. These coatings reflect the invisible NIR light in the solar spectrum to decrease solar heating, but they show visible colours 7. Additionally, passive daytime radia-tive cooling materials create a surface that has high solar reflec-tance and high emittance in the mid-infrared (MIR) transparent window of the atmosphere for saving cooling energy by rejecting solar heating and radiating heat to the cold sky 4,8-12. These materials are suitable for unshaded building roofs to efficiently radiate heat to the outer space or sky, and the ideal installation locations should have long and warm summers to avoid a heating penalty in winters 13,14. For building walls, unlike for roofs facing the sky, the MIR radiative heat exchange is more dominant with outdoor ambient surroundings than with the sky 15. Such radiative heat exchange is more pronounced in urban areas, where buildings are concentrated. Traditional building materials usually show high thermal emissiv-ity 16,17 , leading to intense radiative heat exchange. In hot climates, the overheating caused by high radiation throughput from the hot environment and the sun results in increased cooling demand. Similarly, the excessive radiative heat loss from the building interior in cold climates leads to increased heating energy consumption. A design that minimizes radiative heat transfer through the building wall envelope will therefore be beneficial for both cooling and heating energy savings throughout the year 18. Applying low-emissivity materials to the building envelope has been shown to be a promising strategy 19,20. Metalized and metal films or foils (laminated with other materials) 21,22 and low-emissivity paints containing heat-reflective aluminium (Al) or silver dust as radiant barriers have been proposed to be installed with sufficient air layers, usually within the building envelopes 23. These materials create more reflective surfaces for hollow bricks 24 , roof attics 25 and exterior or interior wall surfaces 26-28. However, regardless of their thermal performance, the state-of-the-art low-emissivity materials are commonly a metallized silver colour and suffer from severe aesthetical limitation, which tremendously hinders their extensive practical applications. It is important to develop materials that satisfy people's aesthetical demands while still achieving energy-efficient buildings. Here we develop a category of coloured low-emissivity films for building wall thermal envelopes, providing a solution to year-round building heating and cooling energy savings. These coloured low-emissivity films aim to realize the thermal regulation and Buildings are responsible for over 40% of total US energy use, of which about 40% is directly related to the operation of heating , ventilation and airconditioning (HVAC) systems. Saving energy to heat and cool buildings would contribute substantially to sustainability. Here we propose a category of coloured low-emissivity films for building walls that constitute the main component of the building thermal envelope. We demonstrate high reflectance (~90%) in infrared wavelength range and selective reflectance in the visible light wavelength range for desired colours. These films can help minimize radiative heat exchange between the indoor and outdoor environments, thus saving energy for all-year cooling and heating while satisfying the required aesthetical effect. Simulations show that these films can help reduce heat gain and loss by up to 257.6 MJ per installation wall area annually. In the case of a typical midrise apartment building, the HVAC system can save up to 124.46 GJ (equal to 9.87% of the building's HVAC energy consumption). By rough estimation, a global CO 2 emission reduction of 1.14 billion metric tons annually could be achieved. Our work provides insights for innovative energy-saving building envelope materials that can help achieve global carbon neutrality and sustainability.
... Most of the energy consumed in the buildings is the airconditioning system to maintain indoor thermal comfort, and the energy consumption is growing rapidly as the fast development in this modern society. World-wide effort s have been made to limit the global energy consumption warming, and vanadium dioxide (VO 2 ) based smart window for buildings has aroused massive attention in the last decades [1][2][3][4] . The VO 2 based smart windows exhibit reversible metal-insulator transition (MIT) accompanying with drastic changes in infrared (IR) transmittance, which made it an ideal material for the regulation of solar heat flux in the energysaving buildings [5] . ...
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The vanadium dioxide (VO 2) based smart windows are developed to reduce energy consumption and improve thermal and visual comfort by controlling the solar flux entering into a building. In this paper, the solo oxygen plasma bombarding is adopted at low temperature (30 °C) for the solar transmission improvement in VO 2 smart windows, which helps to overcome the constraints of destruction in toughened VO 2 windows by annealing. Various oxygen flow rates were used to assist the plasma to identify the influence and mechanism in thermochromic VO 2 films for the first time. The oxygen plasma treatment leads to an effective composition modulation and microstructure reconstruction in the VO 2 films to create new functionalities. The conversion between VO 2 and V 2 O 5 can be controlled and maintained stable during the O 2 flow range of 120-160 sccm (called stable zone). Favorable results are achieved in the stable zone compared with the untreated VO 2 films, the relative improvement of luminous transmission T lum (380-780 nm) is 44%, meanwhile, the increase of T sol (380-2500 nm) is 30% with a negligible decrease of 1.5% in T sol. Additionally, the solar transmission of VO 2 films can be emphatically improved with preserved phase transition behaviors. It reveals that the proposed technique is simple, efficient and performed with ease in working tolerance, and can be applied widely in the VO 2 smart window field.
... Applying low-emissivity materials to the building envelope has been shown to be a promising strategy 19,20 . Metalized and metal films or foils (laminated with other materials) 21,22 and low-emissivity paints containing heat-reflective aluminium (Al) or silver dust as radiant barriers have been proposed to be installed with sufficient air layers, usually within the building envelopes 23 . ...
Article
Full-text available
Buildings are responsible for over 40% of total US energy use, of which about 40% is directly related to the operation of heating, ventilation and air-conditioning (HVAC) systems. Saving energy to heat and cool buildings would contribute substantially to sustainability. Here we propose a category of coloured low-emissivity films for building walls that constitute the main component of the building thermal envelope. We demonstrate high reflectance (~90%) in infrared wavelength range and selective reflectance in the visible light wavelength range for desired colours. These films can help minimize radiative heat exchange between the indoor and outdoor environments, thus saving energy for all-year cooling and heating while satisfying the required aesthetical effect. Simulations show that these films can help reduce heat gain and loss by up to 257.6 MJ per installation wall area annually. In the case of a typical midrise apartment building, the HVAC system can save up to 124.46 GJ (equal to 9.87% of the building’s HVAC energy consumption). By rough estimation, a global CO2 emission reduction of 1.14 billion metric tons annually could be achieved. Our work provides insights for innovative energy-saving building envelope materials that can help achieve global carbon neutrality and sustainability.
... Besides, Su et al. [9] focused on the environmental performance of window-to-wall ratio for different window types in hot summer and cold winter zone in China based on life cycle assessment. Also, Guo et al. [10] measured the energy-saving effect of heat-reflective insulation coating on envelopes in the hot summer and cold winter zone. Regarding air infiltration of the window, Zhou et al. [11] stated that different air infiltration has different impacts on building performance. ...
Article
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... The thermal insulation of an environment proposed by Guo et al., (2012) can save about 5.8kWh/(m2. Month) of electrical energy with air conditioning, considering that a medium can maintain its temperature, no energy will be required to regulate it. ...
Article
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... In recent years, scientific research has focused on the development of engineering methods for calculating, compiling and solving mathematical models that reliably describe the thermophysical processes occurring in enclosing structures under the influence of external climatic factors [13][14][15][16]. ...
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... In recent years, scholars at home and abroad have done a lot of research on external window energy saving.W. Guo [2] et al. discussed the energy saving effects of heat-reflective insulation coating on exterior envelope walls in the hot summer and cold winter zone. V.V.Tyutikov [3] [4] et al. studied simplified evaluation methods for the energy saving and interior air temperature evaluation of glazed spaces, and the presented method can be used for optimizing and showing the energy saving impact as well as the mean, maximum and minimum temperatures of different type of glazed spaces in the preliminary design stage; Elad Negev [5] et al.emphatically analyzed that adding microalgae culture in building windows can provide energy saving for buildings, and solved the main design factors affecting energy saving and other energy aspects; By simulating the full-size model, Marina Aburas [6] et al. concluded that the difference in energy performance of thermochromic windows was 73.4% when the same film type was used in different cities. ...
Article
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On account of the problem which was related to the negative effect of exterior windows energy saving in current residence building, we constructed a single energy-saving building with same structure and different exterior windows. Meanwhile, taking indoor temperature field and building energy consumption as entry points, the key parameters of the energy saving effect of the exterior window were compared and analyzed to study the indoor temperature field and the building thermal load and cooling load in the heating, cooling and transition season of energy-saving buildings which had exterior window structures (standard external windows, blue heat-absorbing glass windows, thermal reflection glass with high light transmission, ordinary hollow glass windows, low-E insulating glazing units, low-E high through glass windows, ordinary 3mm glass windows) with different window frames under the same climate environment. In addition, the grey theory and regression analysis were used to get the correlation degree and matrix equation between the energy-saving effect (the indoor temperature in heating season, the indoor temperature in refrigeration season, the indoor temperature in transition season, the annual cumulative heat load index, the annual cumulative cooling load index, the heating season heat load index, the air-conditioning season cooling load index) and key parameters (the glass thickness, the air layer thickness, the glass layer number, the heat transfer coefficient, the solar heat gain coefficient, the shading coefficient, the solar transmittance, the solar reflectance, the visible light transmittance, the visible light reflectance) in energy-saving buildings.
... (2018)andKarlessi et al. (2011) experimentally studied the impact of different coatings on the daily heat gain. The research results indicated that roof daily heat gain of the white reflective coating was 80% lower than the gray roof.Guo et al. (2012) Schematic diagram and cross-section of a PCM vertical earth to air heat exchanger (VEAHE) system. Partially reprinted and partially redrawn from Liu, Z., Yu, Z., Yang, T., El Mankibi, M., Roccamena, L., Sun, Y., Sun, P., Li, S., Zhang, G., 2019. Experimental and numerical study of a vertical earth-to-air heat exchanger system integrated ...
Chapter
Phase change materials (PCMs) with considerable energy storage density show promise for building cooling performance enhancements, but the cooling performance is highly dependent on novel PCM-integrated forms and intelligent control strategies. This chapter provides a state-of-the-art review of novel PCM-based strategies for building cooling performance enhancements. The strategies investigated include PCM-integrated forms (such as distributed and coupled systems) and combined strategies (such as high-reflective coatings, radiative cooling walls, and hybrid ventilation). Heat transfer mechanisms for both distributed and coupled systems have been characterized to provide an in-depth understanding. Solutions for system performance enhancement of novel PCM-based cooling systems have been comprehensively presented. Future studies and prospects have been demonstrated as avenues for future research. This study presents a systematic overview of novel PCM-based strategies for cooling performance enhancement, together with technical challenges of the widespread applications. Research results are critical for the application and promotion of novel PCM-based cooling strategies in buildings.
... Natural lighting and passive cooling are simply incompatible, but some architectural elements such as external front windows (shutters, roof caps) and reflective surfaces coating can both block direct and reflected sunlight. The visible component of the solar spectrum contributes to the natural lighting of spaces [19,17]. ...
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Buildings sector is the second energy consuming sector worldwide with a share of 40% of final energy consumption. It is responsible for almost a third of greenhouse gases emissions. Therefore, it is essential to regulate the performance requirements based on definition of the acceptable limits specifications of the building envelope depending on the materials type, climate zone and other parameters. In fact, improving the energy in buildings is an ongoing research especially with necessity of developing new low energy materials within the suitably adapted techniques and implementations. Upon several basis set, this paper highlights the adopted solutions by several researchers consisting on integrating local passive and bioclimatic approaches to reap relevant results in terms of energy savings and indoor comfort. In the local context, relying on local materials like limestone rocks and natural fibers such as hemp insulation led to significant reductions in the thermal loads of the building. Full text available for free at (link link till 18 August 2020): https://authors.elsevier.com/c/1bJlW7tbNaHNts
... Consequently, the corresponding norms, standards and regulations on the energy conservation of buildings are inconsistent with the air-conditioning operational situation (Meng et al., 2015), and it can lead to the large difference in both energy efficiency and energy consumption between the actual usage and the primary design. Due to the fact that the heat transfer loss in exterior envelopes of buildings accounts 50-80% of the total heat transfer loss under the continuous operation of air-conditioning and heating systems (Fang et al., 2014;Guo et al., 2012;Peng et al., 2014;Meng et al., 2015aMeng et al., , 2015b, it is of vital importance to improve the https://doi.org/10.1016/j.solener.2020.03.074 Received 6 February 2019; Received in revised form 18 March 2020; Accepted 20 March 2020 thermal performance of the exterior envelopes of buildings, especially the wall body, with the purpose of creating the high comfort level and decreasing the building energy consumption (Jelle, 2011;Meng et al., 2015aMeng et al., , 2015b. ...
... However, this significant progress is still insufficient for stabilizing greenhouse gas concentrations in the atmosphere. Studies have shown that thermal insulation materials have a significant advantage in cost-effectiveness compared with energy saving measures such as solar photovoltaics and wind energy [8,9]. Thus, thermal insulation materials play an important role in energy saving. ...
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Insulation offers thermal comfort by blocking the heat flow across the walls of buildings and drastically reduces the cost associated with energy consumed in maintaining temperature inside the buildings. Commercial insulating materials such as fiberglass, polystyrene, and polyurethane foams, although demonstrating long serviceability, are associated with several limitations including non-biodegradability. This study hence presents the development of biodegradable multilayer nonwoven fabrics based on natural fibers for thermal insulation as a sustainable alternative to synthetic non-biodegradable polymers. The nonwoven fabrics of kapok, jute, and banana with thicknesses ranging between 5 and 15 mm were produced by needle punching. The developed needle punched nonwoven fabrics were attached together in different fiber combinations to produce multilayered fabrics. The nonwoven fabrics were investigated for thickness, areal density, porosity, and thermal properties like heat flux, thermal resistance, and thermal conductivity. The relatively low thermal conductivity of kapok, jute, and banana fibers, and presence of air pockets in the needle punched nonwoven fabrics, all together governed the development of a sustainable fibrous assembly for thermal insulation of buildings. The results confirmed that kapok, jute, and banana fiber based nonwoven fabrics can be successfully used as an alternative to conventional non-biodegradable thermal insulating materials.
Article
Herein, the SiO2 nanoparticles were applied to decrease the thermal conductivity of cellulose acetate (CA) nanofibers via electrospinning and the oxygen-enriched method. Hence, solutions of CA and CA/SiO2 were made by acetone/dimethylacetamide (2 : 1) with oxygen enriching and Helium gas. The nanofiber’s morphology and chemical structures were studied by SEM and FTIR, respectively. Finally, the media’s thermal conductivities were calculated using the two-plate Togmeter device test method based on BS 4745:2005, and the media’s tensile strength features were evaluated under the ASTM D638-10 standard. According to SEM images, SiO2 nanoparticles incredibly covered the whole surfaces of CA nanofibers in the CA/SiO2 medium in a cloud shape. FTIR vibration spectrums confirmed the siloxane bands vibrated at 475/75 cm–1 in the CA/SiO2 mat. Moreover, the thermal conductivity of the CA and CA/SiO2 sheets were 0.1 W/(m K) with 0.225 ± 0.005 mm thickness and 0.044 W/(m K) with 0.461 ± 2.88 mm thickness, respectively. Additionally, the CA medium had 0.5 ± 0.28 MPa tensile stress at 2.57 ± 1.25% tensile strain and the CA/SiO2 membrane had 0.561 ± 0.057 MPa at 1.81 ± 0.939%. Hence, the CA/SiO2 nanocomposite medium has a super low thermal conductivity with good mechanical properties. Therefore, the characterization of the thermal conductivity of cellulose Acetate/nano-SiO2 electrospun nanofiber composites for energy-saving, using an Oxygen-enriched method was completely successful.
Article
Reflective coatings stand at the forefront of sustainable construction, offering a powerful solution to industry challenges posed by climate change, resource scarcity, and rising energy costs. These innovative coatings significantly enhance energy efficiency, improve thermal comfort, and contribute to urban heat management by reducing buildings' absorption of solar heat. This leads to a decreased reliance on air-conditioning systems, resulting in substantial energy savings and a lower carbon footprint for building operations. Our comprehensive study examines these coatings' application on roofs, walls, and windows, confirming their effectiveness in maintaining cooler building interiors and reducing the demand on mechanical cooling systems. By meticulously analyzing materials, application techniques, and modeling methodologies, the paper elucidates the coatings' pivotal role in promoting environmentally responsible building practices. The findings reveal that reflective coatings have the potential to reduce solar heat gain by about 40 %. This reduction can lead to a corresponding indoor temperature drop of 2–4°C in naturally ventilated buildings or a decrease in cooling energy use in air-conditioned buildings, provided the air conditioning system is not undersized. These energy savings are particularly significant in urban environments, where widespread adoption could potentially lower ambient temperatures by approximately 1°C, thus addressing the urban heat island (UHI) effect more effectively. In conclusion, our research offers a quantified assessment of reflective coatings, emphasizing their value within the broader discourse of environmentally responsible construction. Their substantial potential to support urban sustainability objectives is evident, marking them as a promising avenue for future development and implementation.
Article
With a particular emphasis on sustainability, this research investigates the influence of reflectance and emissivity qualities on the amount of energy used by residential buildings of a mid-rise height located in various temperature zones in India. In the first part of the study, the impacts of highly reflecting, cool roofs were evaluated using base-case and proposed simulations. In the second phase, a comparison was made between the possible energy savings that may be obtained by switching from low to high solar reflective roofs. An analysis of the reflectance and emissivity characteristics of the roof was carried out with the assistance of the eQUEST simulation tool. The study findings were validated using the Bureau of Energy Efficiency (BEE) schedule for the residential building energy labeling program. According to the results, highly reflecting roofs, which have a reflectivity of 0.8 and an emissivity of 0.9, dramatically lowered cooling loads by 38% and 20% in hot and dry areas, 21-25% in composite climates, 17-25% in warm and humid climates, and 37% in colder climates. These cost-effective solutions could be applied to existing and new constructions and have the potential to provide large energy and monetary savings by improving the performance of the building envelope, which in turn contributes to efforts to make the building more environmentally friendly.
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Radiative cooling and low-emissivity coatings are promising strategies for building energy savings. Despite their potential, comprehensive assessments across diverse climate zones remain limited. This study addresses this gap by investigating the potential energy performance associated with these coatings in buildings at 250 locations worldwide, spanning all ASHRAE climate zones. To quantitatively assess the energy efficiency benefits, this study employs EnergyPlus simulations to analyse annual thermal energy needs in two-floor, single-family detached apartments with varying levels of thermal transmittance. Results indicate that radiative cooling coatings provide considerable energy-saving effects for most locations, including those with higher heating demands than cooling demands. For buildings with poor insulation, low-emissivity coatings provide substantial annual energy savings in over 74% of the case locations. Moreover, the study also assesses heating penalties due to overcooling effects, revealing that these are generally less critical than the cooling energy savings in most climate zones. Furthermore, a strong linear correlation was found between yearly energy savings and the annual average outdoor temperature for each coating type in zones 0 to 6. The insights from this study have broad implications for the applicability of radiative cooling and low-emissivity coatings in new constructions and existing building retrofits across various climate zones.
Article
This work aims to provide new composite material for thermal insulating building applications. The composite was made with mortar reinforced with natural fibers that were extracted from petiole of WR palm tree. The used fibers were first chemically characterized by EDS, SEM, X-ray and infrared diffractometry spectroscopies as well as tensile test to know their morphological structure. Afterward, the fibers were incorporated into mortar with different mass percentages varying from 0 to 4% to experimentally determine the thermomechanical properties of the manufactured samples. The chemical findings indicated that the WR fibers are rich in cellulose, hemicellulose, and lignin, and possess high crystallinity index; which enhance the mechanical properties and durability of the composite. Furthermore, the obtained density of the composite W2RC4% is of 1305 kg/m3 and less than 2000 kg/m³; this composite can be then classified as lightweight concretes according to the standard NF EN 206+A2/CN (2022). The thermal conductivity and thermal effusivity dropped by about 60% and 42% respectively. Moreover, the WR reduces the compressive strength (76%) and the flexural strength (36%) to minimum values respectively of 5.9 MPa and 3.8 MPa. These values meet the mechanical requirements of lightweight concretes (>3.5 MPa).
Article
To solve the problem of deformation and cracking of ballastless track slab under temperature load, a composite oxide and a series of heat-reflective coating samples were prepared. At the microscopic level, the elemental composition and optical properties of the materials prepared were analyzed by Fourier transform infrared spectroscopy and ultraviolet-visible spectroscopy, and the feasibility of Ce/Si/Ti oxide as functional fillers for heat-reflective coatings of track slabs was demonstrated. At the macro level, by designing and assembling an indoor sunlight simulation test device, the surface and internal temperatures of the coated and uncoated concrete specimens were analyzed and studied, and the macroscopic cooling effect of the coatings was evaluated. Also, to study the engineering application effect of the track slab thermal insulation reflective coating, COMSOL was used to build a 3D calculation model of the heat transfer deformation of the ballastless track slab structure. The research results showed that: Ce/Si/Ti oxide has strong reflectivity and can reflect 95% of infrared light; it has good ultraviolet (UV) shielding ability and can absorb more than 65% of the UV light. The TiO2 coating can reduce the temperature of the concrete surface by 6–11 °C and that of the inside of the concrete by 10–14 °C; the cooling effect decreases evenly with the increase of air temperature. The Ce/Si/Ti oxide coating can reduce the surface temperature of the concrete by 16 °C and that of the inside of the concrete by 15 °. In addition, the cooling effect is basically not affected by the air temperature, and it changes non-linearly with the increase of the Ce/Si/Ti oxide content. Numerical calculation shows that the heat reflective coating can reduce the surface temperature and internal temperature difference of the track slab by 11.54–21.31 °C, and the vertical displacement of the track slab can be reduced by about 35%–70%. Considering the cooling effect, the adhesion strength, and the engineering application effect of the coating, the optimal doping amount of Ce/Si/Ti oxide is 40%, and that coating is the most suitable for use as a ballastless track heat reflective coating.
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The world is facing a rapid increase of air conditioning of buildings. It is the motivation of Annex 80 to develop, assess and communicate solutions of resilient cooling and overheating protection. Resilient Cooling is used to denote low energy and low carbon cooling solutions that strengthen the ability of individuals and our community to withstand, and prevent, thermal and other impacts of changes in global and local climates. It encompasses the assessment and Research & Development of both active and passive cooling technologies of the following four groups:  Reduce heat loads to people and indoor environments.  Remove sensible heat from indoor environments.  Enhance personal comfort apart from space cooling.  Remove latent heat from indoor environments. The present review sums up the state of the art in cooling solutions which may be regarded as resilient. Its main objective is to systematically describe the available cooling solutions, their physical basis, their benefits and limitations, their technology readiness level, their practical availability, and applicability. Doing so, the State-of-the-Art Review forms the basis for the work of EBC Annex 80.
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Nanotechnology and nanomaterials are revolutionizing the construction industry by improving material's durability, strength, and performance. Nanomaterials have a direct impact on building's energy efficiency, façade aesthetics, urban attractiveness, urban pollution, and built heritage preservation. In this paper, it will be confirmed that nanomaterials are providing cutting-edge technical solutions for the European building stock by addressing current biodeterioration and weathering of buildings, reducing CO2 emissions, and having a positive impact on the building sector as a whole, including structure, surface coatings, energy consumption, and COVID-19 outbreak. The methodology used is exploratory and descriptive, with two Italian case studies analysis thrown in for good mixed-methods analysis. The empirical analysis investigates the environmental health and economic benefits of deploying nanotechnology systems in Italian building facades. The objective of the research is to analyze the characteristics and functions of nanoparticles; demonstrating how nano-features can lower energy use, improve contextual urban quality, preserve architectural historical identity, mitigate coronavirus outbreaks, and eventually change the future design thinking process of architects. The paper's originality stems from its synoptic approach and holistic analysis of nanomaterials utilized in Italian façade structures.
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This study investigates the performance of thermal insulation panels composed of the natural Luffa fibres with urea-formaldehyde resin for buildings in the hot arid region. The study has been done experimentally. The work has included the collecting of Luffa fibres from local gardens in Iraq, manufacturing the specimens and measuring the thermal conductivity for different thicknesses, densities and temperatures. The results show that the thermal conductivity of Luffa/urea-formaldehyde composite ranges between 0.22 and 0.25 W/m K. Furthermore, the k-value of the panel may differ by 5–15% depending on the thickness under testing, and by 10–20% depending on the density. However, the main advantage of Luffa composites is that the k-value of the panel is not affected too much at high temperatures, where it has been increased up to 0.26 W/m K (or by 15%) as maximum by the increase of source temperature up to 80°C. This feature has encouraged the use of these panels as external insulation layers in the hot climate region. The results taken from a simulation programme have revealed that the energy saving in the cooling load due to the use of 30-mm insulated panels made of these composites and covered by reflective foils can reach up to 30%.
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Radiative thermoregulation has been considered a promising approach for reducing the heating, ventilation, and air-conditioning (HVAC) energy consumption of buildings and solving the global climate change issues. Electrochromism is a powerful way to dynamically control the heat balance of buildings in response to fluctuating weather conditions, but it has been largely limited to visible and near-infrared wavelength regimes. Here, we develop an aqueous flexible electrochromic system based on graphene ultra-wideband transparent conductive electrode and reversible electrodeposition, which can non-volatilely tune the thermal emissivity between 0.07 (heating) and 0.92 (cooling) with substantial long-term stability and durability. Building energy simulation demonstrates that applying our electrochromic device to building envelopes can save the year-round operational HVAC energy consumption across the U.S., especially in cold climate zone (up to 43.1 MBtu on average among climate zones 5-8). Furthermore, such a dynamic building envelope shows more profound benefits on less insulated buildings, with up to 19.44% of the year-round operational HVAC energy saving for building with only 25% insulation layer, which can serve as a technological solution to retrofit historical buildings or to complement newly constructed buildings with less insulation for lower embodied carbon.
Chapter
Typical analyses of heat transfer across building envelopes consist of determining the thermal resistance of the assembly. The thermal resistance, or R value, is determined through test methods, calculation methods, or numerical simulations. In complex or novel wall assembly configurations, thermal resistance is required to be determined with experiments that use a guarded hot box (GHB) test apparatus according to ASTM C1363, Standard Test Method for Thermal Performance of Building Materials and Envelope Assemblies by Means of a Hot Box Apparatus. One scenario in which complex heat transfer occurs is in a furred airspace in contact with a low emissivity, as the combined effects of natural convection and radiation dominate the heat transfer across the space. Convection and radiation heat‐transfer effects are much more sensitive to the variation in surface temperatures, orientation, and aspect ratio of the airspace. This paper presents the results of ASTM C1363 GHB tests of a full‐scale (8 ft by 8 ft [2.44 m by 2.44 m]) wall assembly containing a furred airspace, with one surface having low emissivity in two configurations. The first configuration is with ¾‐in. (19‐mm)‐depth strapping oriented vertically and spaced at 24 in. (0.61 m.) on center, creating four identical furred airspace cavities approximately 8 ft high by 24 in. wide. The second configuration consists of rotating the same wall assembly by 90°, creating four identical horizontally oriented furred airspace cavities. Each configuration was tested for three exterior temperature conditions: −20°C, −25°C, and −30°C—all with an indoor temperature of 21°C. Additionally, the experimental results were compared with results of the ISO 6946 Annex B.2 calculation method. The results from the tests did not show a significant difference in thermal resistance results between either the exterior temperature differences or when comparing the effects of airspace orientation. This highlights some of the challenges when trying to differentiate small differences between wall assemblies with GHB testing, especially when the experimental uncertainty is considered.
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Many studies have shown that paint with reflective heat can effectively reduce the temperature of the building envelope and reduce the future energy consumption of the building. This study inspired the next-generation inorganic geopolymer material (IGM) color paint without volatile matter, which could be applied on concrete surfaces to reduce energy consumption in warm seasons. In this study, a total of five insulating IGM paints, white, red, green, blue, and yellow, were applied to a 50 cm × 50 cm × 12 cm concrete slab top surface. The highest average light reflectance of all the paints was 87.5% of white IGM paint, which was higher than plain concrete (36.4%). The heat flux and surface temperature were examined in the laboratory, and those test results were verified outdoor. The results showed that the IGM paints could effectively reduce the surface temperature and heat flux of the upper and lower surfaces of concrete slabs, and the white colored IGM paint was the best performer among all five colors, whereas the heat storage coefficient (Sf) of red, white, yellow, blue, and green IGM painted concrete slabs were 0.57, 0.53, 3.62, 2.95, and 1.91 W·m−2·K−1, respectively, lower than plain concrete (24.40 W·m−2·K−1). This coefficient was presented to externalize the thermal admittance. The overall measurement results showed that the concrete slab with colored IGM paints had better heat insulation ability than the plain concrete slab, especially in white IGM paint.
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The present study investigated a specific mall in Chengdu with diverse opaque outdoor surface colors (black, dark grey, dark green, navy blue and yellow). It was revealed that different colors had a variation effect and energy-saving mechanism on the cooling energy saving ratio in hourly, daily, monthly and annual dimensions. These results revealed that for the whole year, the annual cooling load exhibited a differential change. For the whole day, as affected by meteorological factors, especially wind speed, and when the solar radiation is the same, the daily cooling energy saving amounts presented two branches. The global horizontal radiation has a significant positive influence on the daily cooling energy saving amount, but the daily cooling energy saving ratio was not significant. At the hourly level, due to the leading role of wind speed and the diffuse radiation-to-global solar radiation ratio, the hourly cooling energy-saving amount and hourly cooling energy-saving rate presented different branches. When the hourly horizontal solar radiation was the same, the lower the wind speed, the greater the cooling energy savings. Furthermore, the higher the diffuse radiation-to-global solar radiation ratio, the greater the cooling energy savings.
Article
There are many factors that have a major influence on reducing the energy expenditure in building sector. This research aims at qualitative and quantitative assessment of those factors such as double glazed windows, vertical greenery systems (VGS), integrating of semi-transparent photovoltaic device with architectural design of buildings, energy saving by using heat reflecting coating, passive climate control methods, energy saving by shading, building energy performance enhancement by using optimisation technique, double skin green facade, etc. through a holistic and thematic approach. Among the aforesaid techniques, VGS is found the most reliable, efficient and sustainable solution. Attractive VGS can improve the urban environment, increase biodiversity, mitigate pollution also results economic benefit of the buildings as like as energy savings and decreasing surface temperature. Four fundamental energy saving methods are used in VGS which are considered as passive energy saving mechanism. Firstly, interception of solar radiation due to the shadow risen by the vegetation; secondly, vegetation also provides thermal insulation; thirdly, plants evapotranspiration helps for evaporative cooling of building; finally, building blockage makes a variation of wind effect on building. The peak cooling load of ivy coated green building wall has been reduced by 28%. If a VGS is installed without windows and building facing on west, east, south and north correspondingly, the reduction in the cooling load capacity of the building is observed to be up to 20, 18, 8 and 5% respectively. Very high thermally resistive glazed areas on building envelope can be secured via thin film PV glazing and vacuum glazing products with an average U-value of 1.1 and 0.4 W/m²K, respectively. Energy use policies are also helpful to improve energy consumption scenario of buildings. For developing more energy-efficient, sustainable and eco-friendly buildings, these techniques might be helpful for the building designers and architects.
Article
As petrochemical products (including plastics) contribute to the destruction of the natural environment, the use of such products must be reduced. Plastics account for 90% of the insulation materials used in Korea, including extruded polystyrene (EPS), expanded polystyrene (XPS), and urethane foam. Wood-fiber insulation board (WIB) is a promising natural alternative to petrochemical insulation. This study aimed to determine the optimal amount of adhesive resin required for manufacturing WIB. Fire-resistant WIB was prepared with a melamine-urea-formaldehyde (MUF) resin (ranging from 20% to 35%), and the physicochemical and fire-resistant properties were determined. Higher resin content led to improved physical properties, while the thermal conductivity was unaffected. With the exception of 35% resin content in the WIB, the formaldehyde emissions of the WIB samples complied with the Korean Industrial Standards requirements for Super E0 grade (less than 0.3 mg per L). The physicochemical properties of the WIB samples were sufficient for use as an insulating material, even at 20% resin content. A perpendicular flame test revealed that all samples formed a carbonized layer to prevent flame penetration, except for the specimen with 20% of the resin content. The cone calorimeter testing indicated that the MUF adhesives acted as an effective fire retardant at resin contents above 25%.
Article
The building envelopes that integrate heat reflective coatings (HRCs) and phase change materials (PCMs) can block solar radiation from outdoors and have a high thermal inertia, which helps lower the indoor temperature and save the cooling energy costs. However, an inappropriate combination of the two materials could lead to a worse cooling performance. This paper studies the cooling performance of a wall which is coated with the HRC, coupled with a cavity filling the PCM and insulation materials. This work intends to find out the optimal way of integrating the HRC and PCM together to improve the passive cooling performance of the envelope. The effects of the relative positions of HRC and PCM boards on the indoor temperature are studied by comparing 15 combinations of HRCs and PCMs. The results show that the HRC coated on the exterior surface of the wall can block the radiation heat more efficiently than that on the interior surface. An insulation layer between the HRC and PCM is essential to improve the thermal regulation performance of the wall. The insulation layer avoids the fast heat conduction through the PCM and decouples the roles of the HRC as a radiation reflector and the PCM as a thermal storage medium. The thermal conductivity of PCMs, the thickness of PCM layers as well as insulation air gap are also changed to investigate their influence on temperature fluctuations. The RT31/SiO2 (0.09 W/m K) can effectively reduce the indoor temperature by up to 3.6°C compared with the RT31/expanded graphite (EG) (1.25 W/m K). The optimum thickness of both PCM cavity and air cavity are no more than 8 mm. The work provide an insight into the optimal combination of the PCM and HRC in the building envelope for passive cooling.
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Climatic temperature and humidity effects provide the greatest impact on stress–strain state of reinforced concrete structures in the countries with a hot climate. The analysis of temperature and humidity conditions of climatic influences in the countries of Southeast Asia is presented in research, as well as the results of experimental researches of physical and mechanical properties of normal-strength and high-strength concrete, depending on temperature and humidity of the environment accordingly to the tropical climate. The main regularities of the tropical climate effect on the characteristics of physical and mechanical properties of normal-strength and high-strength concrete under axial compression and tension are shown.
Article
The current syntheses of spheres-on-sphere (SOS) microsphere, which possesses both hollow cavity and hierarchical structure, mainly rely on complicated routes and template removal. In this study, a one pot nanoengineering strategy inspired by the automatic transport behavior of water in plants is successfully developed to fabricate SOS microsphere in tandem with a traditional soft template method in the preparation of hollow structure. Amphiphilic siloxane oligomers generated in situ from methyltriethoxylsilane (MTES) under acidic conditions are anchored on the surface of soft template St monomer droplets, sequentially completing hydrolysis-polycondensation and forming a mesoporous polysilsesquioxane (PSQ) shell. Then, the St monomers located in cavity migrate outward under the combined action of capillary force stemming from mesoporous and osmotic pressure generating from inside-outside of the PSQ shell and polymerize on the outside of the hollow PSQ shell, in which residual siloxane oligomers further anchor on the polystyrene (PS) surface to reduce the surface energy of the system, finally resulting in the successful formation of SOS particles. To reduce thermal insulation coefficient of the material, the PS phase in SOS particles is removed to obtain the particles with multiscale hollow structure (SOS-MH), which have more hollow cavities to encapsulate more air. The presence of a much hollow structure in SOS-MH particles enables the thermal conductivity of polyacrylonitrile (PAN)/SOS-MH composite fibrous membranes (0.0307 W m-1 K-1) to decrease by about 40% compared to that of pure PAN fibrous films (0.0520 W m-1 K-1) at the same thickness of 1 mm, and the material also has moisture resistance due to the existence of a hierarchical shell.
Article
Increasing envelope facet albedos considerably reduces solar heat gain, thus yielding building cooling energy savings. Few studies have explored the potential benefits of utilizing cool coatings on building envelopes (“cool-coated buildings”) based on life-cycle cost analysis. A holistic approach integrating the field testing, building energy simulation, and a 20-year life-cycle-based optimization was developed to explore cool-coated building performance and the maximum net savings of optimal building envelope retrofit and design. Experimental results showed that applying cool coatings to a west wall of an office building in Chongqing, China reduced its exterior surface temperature by up to 9.3 °C in summer. Simulation results showed that in Chongqing, making the roof and walls cool could reduce annual HVAC electricity use by up to 11.9% in old buildings (with poorly insulated envelopes) and up to 5.9% in new buildings. Retrofitting old buildings with a cool roof provided the net savings per modified area with present values up to 42.8 CNY/m²; retrofitting a new building with a cool roof or cool walls was not cost-effective. Optimizing both envelope insulation and envelope albedo can achieve 5.6 times the net savings of optimizing the insulation only, and 1.6 times that of optimizing albedo only.
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Cairo experiences extremely high temperatures, which increase buildings’ cooling energy demand. Previous studies found that vegetation raises air temperature in low-density urban areas and has a weak effect on air temperature reduction in high-density urban areas in Cairo. Therefore, this study seeks to investigate the impact of cool paving, as an alternative strategy, on air temperature and buildings’ energy demand reduction in urban areas of different densities. Three built-up areas with varying densities of 25%, 50%, and 85% were selected and simulated by using ENVI-met to evaluate the effect of cool paving on air temperature reduction. Then, DesignBuilder model was used to calculate buildings’ cooling energy savings resulting from air temperature reduction. This study showed that cool paving can reduce air temperature and buildings’ cooling energy in 25%, 50%, and 85% urban densities by 0.5 K – 2.5%, 0.2 K - 1.4%, and 0.1 K - 0.2%, respectively. However, cool paving raised Physiological Equivalent Temperature (PET) in the three areas. Therefore, other scenarios combining vegetation and cool paving are discussed as possible solutions for the dilemma between air temperature and PET reduction. Combining trees with cool paving achieved this balance in the low-density urban area besides reducing cooling energy by 3.2%.
Article
Passive solar design is an effective strategy to alleviate the energy-intensive status of the building sector. Identifying passive solar design parameters that significantly impact office buildings’ energy performance can further understand sustainable design principles and prioritize energy efficiency measures. This study proposes a holistic methodology integrating data mining techniques and parametric energy simulation to explore the critical design parameters in passive solar office building envelopes in hot and humid climates. The data mining module incorporates Extreme Gradient Boosting Decision Tree (XGBoost) and association rule mining to measure feature importance and extract strong correlations, respectively. A case study, using a typical office building in Guangzhou, China as a reference building, is conducted to demonstrate the implementation procedure and feasibility of the proposed approach. In total, 115,200 design scenarios are created and simulated in EnergyPlus software. The results of XGBoost show that the glazing system, window-to-wall ratio, and roof coating are the most critical design factors, with importance scores of 0.4858, 0.3197, and 0.1297, respectively. Similarly, based on a confidence threshold of 30% and a lift threshold of 3.0, the extracted association rules indicate that the above three factors have the strongest correlations with the energy consumption level. Findings of this study will provide practical passive solar design guidance for office buildings in hot and humid climates to achieve energy-saving targets. Also, the developed simulation-based data mining method can be applied to other building types in different climates.
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The article presents the results of experimental and theoretical studies of the thermal insulation qualities of foamed polyethylene with layers of reflective thermal insulation located in its thickness. Currently, the determination of the heat-protection properties of multilayer materials with reflective thermal insulation is carried out experimentally in laboratory conditions. Theoretical studies of the processes of heat transfer in the bulk of such multilayer materials and developed thermophysical model of the heat transfer process through this combined multilayer thermal insulation allowed to develop an engineering calculation method for determining the thermal resistance of multilayer polyethylene foam with reflective thermal insulation from aluminium foil, taking into account thermal conductivity and radiation. The obtained values of the thermal resistance of multilayer polyethylene of various thicknesses by calculation showed the convergence with experimental values. This indicates that reflective thermal insulation with a low emissivity of the surface, located in the thickness of the foamed polyethylene, increases its thermal performance qualities.
Article
Climate-adaptive design, smart control, latent thermal storages, multi-dimensional uncertainty analysis, and multi-objective optimisations are effective solutions for cooling performance enhancement of buildings through integrated techniques, such as hybrid ventilations, nocturnal sky radiation, radiative cooling and active PV cooling for the self-consumption. However, there is no systematic and in-depth analysis on this topic in the academia. In this study, a state-of-the-art review on novel PCMs based strategies to reduce cooling load of buildings has been presented. The investigated strategies include the structural configuration, systematic control and the multi-criteria for assessment. The roles of ventilations, radiative cooling and the underlying heat transfer mechanism have been characterized for the in-depth understanding.In order to realise the multivariable optimal design and robust operations under multi-level scenario uncertainties, parametric and uncertainty analysis, single- and multi-objective optimisations have been comprehensively reviewed, together with technical challenges for each solution. Research results show that, integrated passive and active systems with flexible transitions on operating modes are full of prospects for the multi-criteria performance improvement. Trade-off solutions along the multi-objective Pareto frontier are multi-diversified, dependent on the adopted approach and the studied scenario. Furthermore, machine learning methods are promising for the thermal and energy performances improvement, through the surrogate model development, the model predictive control and the optimisation function. Future studies and prospects have been demonstrated as avenues for future research. This study presents a systematic overview on novel PCMs based strategies, together with the application of machine-learning methods for cooling performance enhancement, which are critical for the promotion of novel PCMs based cooling strategies in buildings.
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In this study the performance of organic PCMs used as latent heat storage materials, when incorporated in coatings for buildings and urban fabric, is investigated. Thirty six coatings of six colors containing different quantities of PCMs in different melting points were produced. Accordingly, infrared reflective (cool) and common coatings with the same binder system and of the same color were prepared for a comparative thermal evaluation. The samples were divided in six groups of different color and eight samples each: three PCM coatings of different melting temperatures (18 °C, 24 °C, 28 °C) each one of two different PCM concentrations (20% w/w, 30% w/w), an infrared reflective and a common coating of matching color. Surface temperature of the samples was recorded at a 24 h basis during August 2008. The results demonstrate that all PCM coatings present lower surface temperatures than infrared reflective and common coatings. Analysis of the daily temperature differences showed that peak temperature differences occur between PCM and common or cool coatings from 7 am to 10 am. Investigating the temperature gradient revealed that for this time period the values for PCM coatings are lower compared to infrared reflective and common. From 10 am to 12 pm, temperature gradients for all coatings have similar values. Thus coatings containing PCMs store heat in a latent form maintaining constant surface temperatures and discharge with time delay. PCM doped cool colored coatings have the potential to enhance thermal inertia and achieve important energy savings in buildings maintaining a thermally comfortable indoor environment, while fighting urban heat island when applied on external surfaces.
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By developing a dynamic model for a retail shed coated with solar reflective materials, this paper aims to compare the annual cooling load, heating load and, as a consequence, the electricity consumption of the shed for six locations around the world. The study employs a range of different coloured coatings with different solar reflective properties, taking into account the effects of roof angle and skin type of the shed. Using these coatings, a comparison of the energy use by electric heating and heat pump has been performed. In addition, other performance issues, such as CO2 emissions and cool roof studies, have been investigated. The modelling and computational results prove that the use of solar reflective coatings is effective in reducing cooling load and overall electricity consumption for most locations, in particular in hot climates with predominant cooling requirements.
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In the determination of sulfur by inductively coupled plasma atomic emission spectrometry (ICP-AES), the sample was dissolved in aqua regia or HNO 3-HCl. The effect of protecting agent potassium chlorate and oxidant perchloric acid on the dissolving was investigated. When the sample was dissolved in aqua regia or HNO 3, all results were little lower, and the difference between determination results was insignificant with or without the presence of potassium chlorate. When HNO 3 or aqua regia was used to dissolve the sample, some sulfur in steel could be oxidized and dissolved in solution and other undissolved sulfur was present in solution with the state of aggregate such as sol or suspended particles. After such heterogeneous sulfur in solution entered into the effective excitation area of ICP through atomization, its spectral excitation rate was lower than the escape rate of sulfur, decreasing the determination results. However, after the sample was dissolved in aqua regia or HNO 3 and then treated with perchloric acid till smoke was out, the sulfur in sample could transferred to sulfate radical and dissolved in homogeneous solution. Therefore, the determination results were accurate and reliable.
Article
Recent tests conducted on a 12,000 ft2 single-story building used as an educational center identified high roof temperatures as a significant problem. The galvanized roof frequently reached temperatures above 180 °F. Considerable heat energy reached the nonventilated attic, resulting in temperatures as high as 105 °F during the peak of summer. Although the HVAC units were equipped with insulated return ducts, these temperatures increased energy conduction through the duct insulation and through the ceiling insulation into the conditioned space. The roof was coated on March 28 and 29, 1995, with a high-albedo acrylic coating developed to control thermal gain and rust. Tests show installation of the thermal-control roof coating reduced the peak roof temperature to 120 °F and significantly decreased the energy flow through the roof and ceiling. Tests show that the high-reflectivity roof coating reduced HVAC energy consumption in a range from 8.7% to 27.5%, depending on the solar radiation and the ambient temperature.
Article
This paper presents an experimental study on the impact of reflective coatings on indoor environment and building energy consumption. Three types of coatings were applied on identical buildings and their performance was compared with three sets of experiments in both summer and winter. The first experiment considers the impact of coatings on exterior and interior surface temperatures, indoor air temperatures, globe temperature, thermal stratification and mean radiant temperatures for non-conditioned buildings (free-floating case); the second one focused on the impact of coatings on reduction of electricity consumption in conditioned spaces; in the third experiment, the impact of different envelope material properties equipped with different coatings was investigated. The results showed that, depending on location, season and orientation, exterior and interior surface temperatures can be reduced by up to 20°C and 4.7°C respectively using different coatings. The maximum reduction in globe temperature and mean radiant temperature was 2.3°C and 3.7°C in that order. For the conditioned case, the annual reduction in electricity consumption for electricity reached 116kWh. Nevertheless, the penalty in increased heating demand can result in a negative all-year effect in Shanghai, which is characterized by hot summers and cold winters.
Article
This book is a practical guide that presents the current state of knowledge on potential environmental and economic benefits of strategic landscaping and altering surface colors in our communities. The guidebook, reviews the causes, magnitude, and impacts of increased urban warming, then focuses on actions by citizens and communities that can be undertaken to improve the quality of our homes and towns in cost-effective ways.
Article
This paper reports the measured solar spectral properties and the thermal performance of 10 prototype cool colored coatings, developed at the National and Kapodistrian University of Athens, using near-infrared reflective color pigments in comparison to color-matched, conventionally pigmented coatings. These coatings are developed to be used in the urban environment to fight the heat island effect. The spectral reflectance and the infrared emittance were measured and the solar reflectance of the samples was calculated. The surface temperature of the coatings when applied to concrete tiles was monitored, using surface temperature sensors and a data logging system, on 24 h basis from August to December 2005 in an effort to investigate the ability of the cool colored coatings to maintain lower surface temperatures than conventionally pigmented color-matched coatings. The data obtained has been extensively analysed and indicate significant success in the development of these cool colored coatings. It was found that all the coatings containing infrared reflective pigments have solar reflectance values higher than those of standard coatings. Furthermore, it was demonstrated that cool colored coatings maintain lower surface temperatures than color-matched conventionally pigmented coatings. This temperature difference is mainly due to differences in solar reflectance. These cool colored coatings can be used on buildings (roofs and walls) and other surfaces in the urban environment. Thus, at building scale, the use of cool colored coatings with increased solar reflectance can improve building comfort and reduce cooling energy use, and at city city-scale it can contribute to the reduction of the air temperature due to the heat-transfer phenomena and therefore improve outdoor thermal comfort and reduce the heat-island effect.
Article
Low-income households in developed and less developed countries suffer from serious indoor environmental problems such as heat stress, lack of comfort and poor indoor air quality. Passive cooling of buildings and in particular solar and heat protection techniques, heat dissipation and heat amortisation techniques have reached a very high degree of maturity. New technological developments have proven extremely efficient in decreasing the need for cooling and improving indoor environmental conditions. Developments on the field of solar and heat protection, such as highly reflective coatings for the urban environment and the building envelope and new knowledge and developments on the field of ground and convective cooling and ventilation, may help low-income citizens to considerably improve their quality of life during the overheating period. These new developments are characterised by low cost and are easy to apply.This paper investigates the potential of the more promising new developments on the field of passive cooling, like the cool reflective coatings to improve outdoor and indoor conditions of low-income households in warm areas of the planet, ground cooling using earth to air heat exchangers, and discusses the potential of new ventilation techniques and systems for improving indoor comfort and air quality. Results show a very high potential to improve indoor environmental conditions and contribute towards higher passive survivability levels.
Article
Buildings are large consumers of energy in all countries. In regions with harsh climatic conditions, a substantial share of energy goes to heat and cool buildings. This heating and air-conditioning load can be reduced through many means; notable among them is the proper design and selection of building envelope and its components.The proper use of thermal insulation in buildings does not only contribute in reducing the required air-conditioning system size but also in reducing the annual energy cost. Additionally, it helps in extending the periods of thermal comfort without reliance on mechanical air-conditioning especially during inter-seasons periods. The magnitude of energy savings as a result of using thermal insulation vary according to the building type, the climatic conditions at which the building is located as well as the type of the insulating material used. The question now in the minds of many building owners is no longer should insulation be used but rather which type, how, and how much.The objective of this paper is to present an overview of the basic principles of thermal insulation and to survey the most commonly used building insulation materials, their performance characteristics and proper applications.
Article
This paper presents the results of a comparative study aiming to investigate the effect of reflective coatings on lowering surface temperatures of buildings and other surfaces of the urban environment, and thus test their suitability to lower ambient temperatures and fight the heat island effect. In total, 14 types of reflective coatings, selected from the international market were studied, from August to October 2004, on a 24 h basis. These coatings are used in buildings and some of them are used or could be used in the future in other surfaces of the urban environment (sidewalks, parking lots, etc.). In order to investigate the thermal performance of the reflective coatings, surface temperature sensors and a data logging system as well as infrared thermography procedures were used. The spectral reflectance and the infrared emittance of the samples were also measured. The collected data have been extensively analyzed. It was demonstrated that the use of reflective coatings can reduce a white concrete tile’s surface temperature under hot summer conditions by 4 °C and during the night by 2 °C. It can be warmer, than the ambient air by only 2 °C during the day and cooler than the ambient air by 5.9 °C during the night. “Cool” coatings present superior thermal performance even compared to other “cool” materials. This study can assist in choosing more appropriate coatings for building envelopes and other surfaces of the urban environment, and thus contribute to the mitigation of the heat island effect as well as the reduction of cooling loads and electricity consumption of buildings.
Article
Owners of homes with pitched roofs visible from ground level often prefer non-white roofing products for aesthetic considerations. Non-white, near-infrared-reflective architectural coatings can be applied in situ to pitched concrete or clay tile roofs to reduce tile temperature, building heat gain, and cooling power demand, while simultaneously improving the roof's appearance. Scale-model measurements of building temperature and heat-flux were combined with solar and cooling energy use data to estimate the effects of such cool-roof coatings in various California climates. Under typical conditions—e.g., summer afternoon insolation, R-11 attic insulation, no radiant barrier, and a 0.3 reduction in solar absorptance—absolute reductions in roof surface temperature, attic air temperature, and ceiling heat-flux are about 12, 6.2 K, and , respectively. For a typical house with R-11 attic insulation and no radiant barrier, reducing roof absorptance by 0.3 yields whole-house peak power savings of 230 W in Fresno, 210 W in San Bernardino, and 210 W in San Diego. The corresponding absolute and fractional cooling energy savings are (5%), (6%), and (1%), respectively. These savings are about half those previously reported for houses with non-tile roofs. With these assumptions, the statewide peak cooling power and annual cooling energy reductions would be 240 MW and , respectively. Statewide energy savings would reduce annual emissions from California power plants by 35 kton CO2, 1.1 ton NOx, and 0.86 ton SOx. The economic value of cooling energy savings is well below the cost of coating a tile roof, but the simple payback times for using cool pigments in a roof tile coating are modest (5–7 yr) in the warm climates of Fresno and San Bernardino.
Article
Studies, around the world, have demonstrated that envelope colour has significant effect on building thermal performance and the use of thermal mass can usefully modify the thermo-physical signature of buildings. However, their influences under hot-humid climate have not been investigated in details. In view of the issue, a testing facility has been established in the Department of Architecture of the Chinese University of Hong Kong; the facility allows study of the effect of various building design features on indoor temperatures. This paper presents the results of investigation about the effect of envelope colour and thermal mass on indoor temperatures. The study reveals that the use of lighter surface colour and thermal mass can dramatically reduce maximum indoor temperatures. However, their applications in building design could be very different, and to a large extent, depend on the circumstance. Furthermore, the paper demonstrates the possibility to develop predictive formulas for daily maximum indoor air temperature.
Article
The effect of external surface colour on the thermal behaviour of a building has been studied experimentally as well as theoretically. Experiments were performed on scaled down units of 1 m3 volume, under different conditions; namely (i) completely tight building, (ii) effect of opening the door and (iii) of an overhang on the window for complete shading throughout the day. A computer simulation programme, based on periodic solution of the heat conduction equation, was developed to yield the time variation of the room temperature corresponding to the given meteorological parameters. As expected, the black painted enclosure recorded a maximum of 7°C higher temperature than the corresponding white painted enclosure during hours of maximum solar radiation, while during the night the two enclosures showed nearly the same temperatures (being the light weight constructions). The experimentally observed temperature meaasurements were quite consistent with the theoretical calculations within experimental accuracies (±2°C). The same software when used to simulate the behaviour of a normal sized heavy structure, predicted 4°C to 8°C higher temperature throughout a period of 24 hours for a black coloured surface than the corresponding white one.
Effect of building materials on internal temperatures
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Properties of waterborne solar-reflective heat-insulating coatings
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