Reflective Paint Research Articles

Thermal sensitivity and potential cooling-related energy saving of masonry walls through the lens of solar heat-rejecting paints at varying orientations

This study aims to analyse the thermal efficiency of wall elements with varying position-allocation-thickness of insulation, in the aspect of the optical properties of their external paint. A special focus has been placed on the role of solar reflectivity in wall coatings while taking into account the impact of the ambient environment at all cardinal points. In this light, the problem of urban environment warming must be addressed, while considering occupant reliance on air-conditioning. In the initial stage, the key research objective is to shed some light on the performance of analysed wall assemblies in terms of thermal sensitivity (decrement factor and time lag). On the other hand, at the targeting stage, our main intention is to demonstrate the eminence of solar heat-rejecting paints on the cooling power demand of wall arrangements. Furthermore, this work is extended to the assessment of the overall heating and cooling demands on an annual basis. A thermal-network model is developed within this framework to determine temperature variations and heat fluxes in the margins of the examined setups. The potential benefits of the suggested model are twofold. Accordingly, the findings of the numerical analyses reveal the configurations and operating conditions proving the optimal dynamic thermal parameters and energy demand. Numerical simulations indicate that an optimal cooling power capacity is noticeable for wall surfaces covered with solar heat-rejecting paints; cooling saving can exceed 90% for highly solar-reflective surfaces. However, when it comes to unveiling the global performability of ultra-white paints the overall improvement of conditions may vary radically; a reflective paint will probably not be sufficient to counterbalance both heating and cooling concerns. In terms of annual heat transmission loads, results exhibit an optimal solar absorptivity of 0.35 for north/east/west facing walls and 0.75 for south-oriented walls. Also, within the confines of our attention, by the increase of insulation level, the energy benefit can reach up to 40% per annum.

Analysis of the Application of Green Building Concepts in Educational Buildings Case Study: Building B, Faculty of Biology UGM Yogyakarta

Abstract. The building sector is one of the world's largest energy consumers. This problem is further exacerbated by our dependence on non-renewable energy sources. More than 90% of the world's energy comes from fossil energy including oil, natural gas and coal whose availability in nature continues to decrease because they cannot be renewed. Green design is a reaction to the global environmental crisis. Green design which also leads to eco design, or design for environment is the art of designing physical objects and the surrounding environment to balance sustainable principles with economic, social, and ecological aspects. As a construction actor, you are required to be able to produce a building design that does not require too much energy consumption and also of course considers the comfort of the occupants in it. In an effort to develop the campus, Universitas Gadjah Mada seeks to make the UGM campus a Green Campus. One of the buildings at UGM and the first building at UGM to be certified as a green building by the Green Building Council Indonesia (GBCI), namely Building B, Faculty of Biology UGM with 43% energy savings points, 30% water and 65% efforts to utilize local materials . From the Energy sector, this building applies a small percentage of window/glass openings, uses reflective paint so as to minimize heat that will be transmitted into the building, external shading devices (shading), applies insulation on the roof, a variable refrigerant type HVAC system (VRF). ) with a high COP so that it can save more energy and use artificial lighting / energy-saving lamps. From the water sector, using a toilet fixture with a low flow so that it can save water. Meanwhile, the use of materials includes the use of clay tiles, hebel walls and other materials that are local products.

An investigation towards the optimum design of retro-reflective materials as building envelopes for the enhancement of optical performance

Retro-reflective (RR) materials may represent an advanced solution for building envelopes, as they could contribute to Urban Heat Island mitigation. This study could bring novelty to the current state of the art on this topic, as it proposes to investigate the optimum design of glass beads RR materials for building application. To this aim, the impact of glass beads superficial density and diameter on the optical performance of RR materials has been further explored. In particular, 15 RR glass beads samples were developed, using a highly reflective paint as substrate and varying both glass beads superficial density and diameter. Also a diffusive sample, without RR glass beads, was made for comparison. Three different glass beads superficial density ranges and five diameter ranges were investigated. Samples were tested through spectrophotometric and angular reflection distribution analysis. All RR samples exhibited an overall lower solar reflectance compared to the diffusive sample, whereas RR samples with 200 ÷ 300 µm diameter exhibited the highest RR capability. By reducing glass beads superficial density, generally a reduction of RR performance was observed.

Heat Reflective Thin-Film Polymer Insulation with Polymer Nanospheres—Determination of Thermal Conductivity Coefficient

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.

Investigation of Cool Roof Based on Reflective Paints, Evaporative Cooling, and Shading

Abstract In this study, three different approaches are investigated for keeping the roof cool and reducing the heat flow inside a building located in Kanpur, India. In the first approach, various reflective paints are investigated and their performance degradation over a year is examined along with the cost-benefit analysis. In the second approach, the roof surface is kept wet, and due to water evaporation, the roof was kept cool. In the third approach, the effect of shading on the rooftop surface temperature is studied. It is observed that without any cooling, the rooftop temperature can rise about 20 °C above the ambient air temperature. The application of white acrylic paints can reduce this temperature rise to about 5–7 °C. However, after a year due to degradation, this temperature rise is about 10–12 °C. Using evaporative cooling the rooftop temperature can be lowered even below the ambient air temperature by about 3 °C. However, this approach will require active management of the system and consumption of water. The cost for the first two approaches is estimated to be about 5–6 Rs./sq.ft with a payback time of 2 years. Shading can reduce the temperature rise to about 5 °C. Structures meant for other purposes such as photovoltaic panels can serve the additional benefit of cooling the roof. Shading seems to be a robust and low-maintenance option, and cost analysis of structures meant primarily for shading the roof needs to be explored.

Effects of Natural Weathering on the Performance of High Solar Reflective Index Paint Surfaces Exposed in Harsh Climatic Conditions of United Arab Emirates

The solar reflective index (SRI) is one of the important parameters in the analysis of a building’s energy and thermal performance, especially for “cool” reflective paints or coatings and also for cool roof membranes. However, there exists less information on the typical performance of the cool materials exposed for long term in the Middle East and more specifically in the United Arab Emirates (UAE). In this study, we determined values of reflectance, emittance, solar reflective index (SRI), and color difference, for three different high-SRI white-paint-coated panels exposed naturally on low- and high-sloped racks for three years. After 3 years, reflectance values of exposed sample panels significantly decreased with an increased color difference in comparison with original unexposed paint surfaces. The emissivity of the paint changed very little for all of the exposed samples, but SRI, determined from both the reflectance and emittance, initially ranged between 95 and 110 and decreased to 60–90 after three years of exposure. This appeared to be related to exposure to high temperatures, UV radiation, and adhesion of airborne contaminants in conjunction with low precipitation. Macroscopically, panels exposed on a low slope were the most discolored with the greatest presence of dust infusion and reduction in increase in surface temperatures, which was demonstrated through thermal imaging. Such natural weathering research study is necessary for the development of standard exposure tests and for the determination of various control elements to increase the durability of cool materials in hot and arid climatic conditions of the UAE.

A rapid method for producing highly diffuse reflective white paint as the back surface reflector in dye-sensitized solar cell

Reflective paint, fabricated from dye and pigments, has attracted considerable attention given its easy production and various applications. In this work, in a rapid process, we produced highly diffuse reflective white paint based on barium sulfate as a pigmented diffuse reflector (PDR) with 99% reflection to be used as the back surface reflector solar cells. Employing barium sulfate as pigments paves the way for fabricating cost-effective reflective paints with high durability and UV resistance. The paint was applied on the back surface of the counter electrode in a TiO2 nanoparticle-based dye-sensitized solar cell (DSC) which improved the power conversion efficiency (PCE) from 3.47% (in the absence of any reflective layer) to 4.78% (in presence). The developed BaSO4 highly diffuse reflective paint can be applied to a wide range of substrate materials with different methods for various applications.

Helping wildlife beat the heat: Testing strategies to improve the thermal performance of nest boxes

ABSTRACT Nest boxes are often deployed in an attempt to offset the loss of natural tree hollows following landscape disturbance (e.g., land clearing, logging and wildfire). However, nest boxes can experience more variable and extreme microclimates than natural hollows, which could harm animals that use them. In this study, we tested the thermal performance of candidate nest box designs prior to their deployment for greater gliders (Petauroides volans) in forests impacted by the 2019–2020 bushfires. The tests were conducted under controlled laboratory conditions to investigate the thermal response of different designs to radiant heat and changes in ambient temperature. We examined how paint type (i.e., no paint, white exterior paint, and reflective white paint), insulation thickness (0 mm, 20 mm, and 40 mm Foilboard), and insulation amount (i.e., number of sides insulated) influenced the internal temperature profiles of these nest boxes. We found that nest boxes with the reflective white paint had the lowest temperatures on the inside wall closest to the radiant heat source, but internal nest box air temperature did not differ among paint treatments. Similarly, the internal wall closest to the radiant heat source was cooler in nest boxes with thicker compared to thinner insulation, but there was no difference in internal air temperature between the two thicknesses. Both 20 mm and 40 mm Foilboard insulation resulted in significantly cooler air temperatures and internal wood panel temperatures compared to nest boxes without insulation. Fully insulated nest boxes and those with three of the four sides insulated exhibited less temperature variability and remained cooler than the less-insulated nest boxes. Temperatures inside nest boxes with more than one side insulated took longer to increase and decrease in a convective heat chamber, but importantly, never reached the heat extremes (> 40°C) of less insulated nest boxes. Fully insulated nest boxes also maintained heat longer than any other nest box type in a cold room. Understanding how different construction materials influence nest box temperature profiles and identifying designs that minimise thermoregulatory costs for animals is important for the safe implementation of nest box programs.

Enviro-economic assessment of buildings decarbonization scenarios in hot climates: Mindset toward energy-efficiency

As buildings consume a considerable portion of the global energy output and have a key role in greenhouse gas emissions, several steps have been taken to lower the energy and emissions from buildings especially through the adoption of renewable energy sources. The emerging building integrated photovoltaic (BIPV) technologies act as replacements for conventional building envelopes as well as energy generation sources. The purpose is examining, through parametric analysis, the potentials of energy-efficient building solutions in different hot climatic regions. Through an enviro-economic assessment, a building envelope solution is proposed that enhances the building energy performance in terms of reducing the building energy use, generating green energy, and reducing indoor thermal discomfort. Results showed that CO2 emission reductions ranged from 9% to 31% and the discomfort hours reductions ranged from 10% to 25% based on the model specifications. Moreover, several financial elements were considered such as IRR, ROI, NPV and the Payback period were calculated for each model. Promising numbers were obtained in terms of the economic analysis of the models. The models demonstrate an IRR index of 26.45%, 21.6%, and 16.85% for Aswan, Cairo, and Alexandria, respectively, an ROI index of 18.32%, 15.68%, and 13.23% for Aswan, Cairo, and Alexandria, respectively, with nearly half the PBP in all locations. According to the techno-economic outcomes, the Reflective paint model integrated with the Glazing Integrated PV tends to be the most cost-effective implementation in the three different locations.

Thermal performance of building prototype with different cool roof structures in composite climate

ABSTRACT In the domestic sector, buildings contribute to about 55% of the total energy consumption for space heating and cooling. In this study, an experiment was carried out using a square shape building prototype made up of laminated plywood with Reinforced Cement Concrete (RCC) roof. Surface treatment of four types of reflective paints was applied on the RCC roof slab. Their performance was monitored in the summer season (April and May). Based on the peak temperature of interior and exterior roof layers, several important parameters, such as temperature, indoor thermal amplitude, time lag, decrement factor, thermal damping, thermal performance index, peak degree hours and thermal performance of each roof slab, were analysed. The application of cool roofs (CR-1, CR-2, CR-3, and CR-4) shows a significant reduction in indoor temperature (2.1°C–3.2°C), and indoor thermal amplitude (16.10%–27.94%) compared to a standard RCC roof. The drops in peak temperature of exterior and interior roof layers were 4.8°C–6.8°C and 3.9°C–6.3°C, respectively. A significant improvement was achieved in time lag and decrement factor (3–4 h more than the reinforced concrete roof), with energy savings varying from 10.58% to 13.73%.

Energy, comfort, and environmental assessment of passive techniques integrated into low-energy residential buildings in semi-arid climate

Residential buildings consume a lot of energy, particularly after the recent pandemic and remote working lifestyle. Thus, it is crucial to design energy-efficient buildings that reduce energy consumption without losing indoor thermal comfort. In this regard, integrating affordable passive strategies can improve thermal comfort, energy efficiency, and other environmental setbacks. In this study, several passive techniques were parametrically analyzed and tested in real semi-arid conditions using building simulation tools. The analyzed passive strategies include a phase change material (PCM), reflective paint, insulation, double-clear glazing, double low-E glazing, reflective glazing, and shading. Three of Monterrey’s major energy-consuming typical houses were analyzed, and the optimum configuration was selected based on annual energy saving and initial material cost-effectiveness. Although the PCM was thermally effective when integrated into walls and roofs, as well as in terms of total energy reduction, the results showed that it was not cost effective. Therefore, insulation and reflective paint in walls and roofs were applied in conjunction with low-E glazing and shading in all cases to save more than 50% of energy annually. The use of these energy-saving techniques increased the hours of comfort by up to 45%, resulting in a reduction of up to 3000 kgCO2e.

“The contribution of double skin roof coupled with thermo reflective paint to improve thermal and energy performance for the ‘Mozabit’ houses: Case of Beni Isguen’s Ksar in southern Algeria”

In traditional cities of hot and arid climate regions, roofs are usually the surfaces most exposed to intense sunlight in summer. This leads to high temperatures inside the houses and forces the inhabitants to escape to the terraces at night. On the other hand, some residents use air conditioning and therefore increase energy consumption. This work aims to study the contribution of a double skin roof coupled with a thermo-reflective paint on the reduction of indoor temperature and energy consumption in house located in the Ksar of Beni Isguen in southern Algeria. Firstly, the problem of overheating was identified through temperature and humidity measurements for traditional dwelling in hot season. Secondly, a model of double skin roof coupled with thermo-reflective paint was developed and numerically simulated using TRNSYS software. The obtained results showed that in summer, the temperatures in traditional houses are high compared to the comfort zone. The average indoor operating temperatures exceeded 37 °C during different hours of the day, over the investigation period of three representative days of hot season. Nevertheless, the proposed model reduces the indoor operative temperature by 5 °C. Also, the model was validated against in situ measurements, whose results showed a consistency between the measured and simulated temperature values. In addition, thermal simulation results performed over a period of one year indicate that the overall energy consumption required for cooling loads is reduced by 572 kWh i.e. 66% when optimizing the roof thermal performance.

Energy-Efficient Building Design for a Tropical Climate: A Field Study on the Caribbean Island Curaçao

Based on an extensive literature review on passive building designs for tropical climates, seven energy-efficient building design principles for tropical climate areas were deduced. These are: 1. To orientate a building design in such a direction that it protects from excessive solar radiation; 2. To accommodate for indoor natural ventilation; 3. That it makes maximal use of indirect instead of direct natural light; 4, That it reduces the amount of heat transmission through the roof as much as possible by natural ventilation between roof and ceiling and by lowering the roof surface temperature; 5. By preventing the use of high thermal mass materials; 6. By reducing through the exterior walls as much as possible heat transmission by e.g., preventing direct sunlight on the external walls and applying reflective paints on the external walls and; 7. By creating outdoor and transition spaces such as balconies, terraces atriums and corridors. The insights from the literature review were used as input to conduct a field study to evaluate the practice of applying passive building design principles. To this end, for 626 buildings on the Caribbean island Curaçao, it was investigated to what extent the recommended passive design principles for tropical climates were actually applied. Based on the results of the field study, several recommendations are made to improve the practice of applying passive building principles.

Impact of light-colored paint materials on discomfort in a building for hot-dry climate

India is a tropical country with diverse climates, and thermal adaption plays a significant role in sustaining thermal comfort in non-conditioned buildings. Indoor air temperature is taken as the main parameter for thermal comfort in buildings, which is very high in western India and creates uncomfortable for occupant. Thermal comfort is a primary need inside the buildings from a human health perspective. Roof structure and the color of the exterior surface affect the thermal comfort of the buildings in a hot-dry climate. Roof contributes maximum heat gain towards the outdoor temperature wave amplitude and time lag in non-conditioned buildings during summer. Three commercially available reflective paints or coatings were selected and used in the simulation to assess the performance of a non-conditioned building. In this paper, we present the evaluation ofthe discomfort index (DI) and Tropical Summer Index (TSI) for the summer season (April and May).The comfort hours achieved using cool roof coatings were 12–17 hours more than the base case or conventional roof used in a hot-dry climate. The tropical summer index (TSI) was found adequate within its comfort range (27.5 °C) for roofs with surface coatings than a base case roof slab.

Building envelopes toward energy‐efficient buildings: A balanced multi‐approach decision making

The worldwide environmentally friendly trend has focused the last decade on emphasizing the value of energy conservation and reducing the carbon footprint in buildings, achieving zero energy buildings. Presently, viable building techniques, in developing countries, are insufficient to achieve zero energy buildings. Thus, authorities should implement policies mandating new developments and renovations to establish “energy-efficient buildings”; nevertheless, design solutions should be properly evaluated and assessed preceding execution. The conservation of energy without jeopardizing human comfortability is a huge challenge for any designer. Occupants are less interested in making a major investment to save some expenses over the next two decades, especially nowadays that energy is still affordable. Therefore, improved indoor environmental conditions are perhaps another important parameter toward energy-efficient buildings. Through dynamic simulations, this study examines the energy efficiency and thermal comfort achieved by integrating retrofitting strategies in an institutional building in three different American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) hot climate zones represented by three cities of Egypt (Aswan, Cairo, and Alexandria). The built-up baseline model is validated using actual energy usage data. The validated baseline model is then subjected to local sensitivity analysis to determine the driving parameters influencing the building's energy demand. The study at hand focuses on a broader perspective on sustainability. With a multiapproach decision-making methodology based on the most recent measures, the study highlights the outcomes through an environmental–economic assessment and indoor thermal comfort depending on experts' weighting, responses, and recommendations. The outcomes postulate that the implementation of reflective paints solutions would achieve the highest percentages of whole-building energy savings with 21%, 19%, and 17% for Aswan, Cairo, and Alexandria, respectively, improving indoor thermal comfort levels.

The Effect of the Substrate on the Optic Performance of Retro-Reflective Coatings: An In-Lab Investigation

Retro-reflectivity is a promising surface capability, which has attracted the interest of researchers for building applications in order to counteract Urban Heat Island (UHI) effects. This work aims at studying the impact of the substrate material on the optic performance of retro-reflective (RR) coatings. Three types of substrate materials were investigated: smooth pine wood panels, rough plywood panels, and smooth acetate sheets. The RR coating samples were made by firstly adding a high reflective white paint onto the substrate material and a homogeneous RR glass beads layer on the top. As a reference case, also diffusive samples, without RR beads, were developed. Samples have been tested through a spectrophotometric and an angular reflectivity analysis. Results show that, despite a lower global reflectance of the RR samples with respect to the diffusive ones, the glass beads coating provides a good retro-reflective capability to all the diffusive samples. Additionally, the roughest RR sample exhibited the highest RR capability of up to 16%, with respect to the other smoother samples. Future developments may involve the optimum design of RR coatings, in terms of their optic performance by varying the substrate materials and roughness, the glass beads density and dimension.

Use of hollow silica and titanium dioxide microparticles in solar reflective paints for daytime radiative cooling applications in a tropical region

Passive radiative cooling provides an energy-saving method for heat management in buildings. Solar reflective paints are versatile and scalable formats that can be readily applied for this cooling technology. We investigate solar reflective paints consisting of hollow silica (SiO2) and hollow titanium dioxide (TiO2) microparticles as pigments and methyltrimethoxysilane as a binder. The hollow microparticles are synthesized via sol-gel and etching methods to control their diameter. Paint formulation is optimized for high total solar reflectance, measured by a UV-visible-near infrared photospectrometer, without exceeding the critical particle volume content. By introducing air volume into the particles and selecting optimal particle size, solar reflectance of the dry paints is significantly improved. Compared to TiO2 microparticle samples, paints with hollow SiO2 microparticles are more effective at rejecting solar irradiation on average while also requiring less particle volume content. Thermal and spectral emissivity measurement also indicates that the hollow SiO2 microparticle paint has the highest broadband infrared emission, followed by a commercial paint and a TiO2 sample. Outdoor experiment in a tropical climate demonstrates that the paint with hollow SiO2 microparticles has better cooling performance than a commercial cooling paint product. The results suggest the potential of hollow SiO2 microparticles for improving radiative cooling paints.

Energy Consumption Reduction by High Solar Reflective Paint

Energy Consumption Reduction by High Solar Reflective Paint

High-Resolution Modelling of Thermal Exposure during a Hot Spell: A Case Study Using PALM-4U in Prague, Czech Republic

The modelling of thermal exposure in outdoor urban environments is a highly topical challenge in modern climate research. This paper presents the results derived from a new micrometeorological model that employs an integrated biometeorology module to model Universal Thermal Climate Index (UTCI). This is PALM-4U, which includes an integrated human body-shape parameterization, deployed herein for a pilot domain in Prague, Czech Republic. The results highlight the key role of radiation in the spatiotemporal variability of thermal exposure in moderate-climate urban areas during summer days in terms of the way in which this directly affects thermal comfort through radiant temperature and indirectly through the complexity of turbulence in street canyons. The model simulations suggest that the highest thermal exposure may be expected within street canyons near the irradiated north sides of east–west streets and near streets oriented north–south. Heat exposure in streets increases in proximity to buildings with reflective paints. The lowest heat exposure during the day may be anticipated in tree-shaded courtyards. The cooling effect of trees may range from 4 °C to 9 °C in UTCI, and the cooling effect of grass in comparison with artificial paved surfaces in open public places may be from 2 °C to 5 °C UTCI. In general terms, this study illustrates that the PALM modelling system provides a new perspective on the spatiotemporal differentiation of thermal exposure at the pedestrian level; it may therefore contribute to more climate-sensitive urban planning.

TEMPERATURE MODELLING IN ASPHALTIC CONCRETE FACINGS, THE REFLECTIVE SURFACE EFFECT SIMULATION CASE STUDY: GHRIB DAM (AIN DEFLA, ALGERIA)

The asphaltic concrete facing is one of the most widely used components for waterproofing rockfill dams. It is, particularly in the case of hydroelectric pumped storage facilities, often highly exposed to significant temperature fluctuations, which are caused by solar radiation, variation in the water level in the reservoir, frost in the winter season, as well as wind speed and direction, and precipitation. To better explain the heat transfer phenomenon, it is necessary to know the temperature variations in the different layers of the asphaltic concrete facing. This study describes the measurement of the temperature in the asphaltic concrete facing (raw and protected) of the Ghrib dam (Ain Defla, Algeria) and its evaluation using a numerical model of the heat flow using the Fluent software. First, a validation of the model by comparison with experimental measurements, in the case of a daily variation in ambient temperature, the comparison of the results of the calculation of the numerical model with the real measurements shows an excellent similarity. Then we simulate the application of thermal protection by adding a reflective paint to the facing surface. The results of this simulation show that the reflection of solar radiation by the reflective surface has the potential to cool the asphaltic concrete facing and reduce the temperatures significantly, the temperature peak as well as reduce it to 11.47 °C, this happens at noon when the heat is very high, which is significant for our asphaltic concrete facing, where the temperatures reach their maximum values (49°C) in the raw case (without protection).