Membrane Roof Research Articles

Feasibility of a snow-melting membrane roof with an electrical–thermal system and prediction of its performance

Snow removal from membrane structures used for roofing is a critical activity to effectively avoid collapse accidents caused by non-uniform snow distribution. Electrical–thermal systems that combine electrical with thermal techniques are proposed as a substitute for chemical and mechanical snow removal methods. These systems overcome the problems of conventional chemical-based snow- melting in construction material corrosion and environmental pollution. The aims of this study are to analyze the performance of an automatic snow-melting membrane roof utilizing an electrical–thermal system with heating wires, determine the suitable heating wire parameters and climatic conditions based on the snow-melting performance, and evaluate the system using experimental data. The findings indicate that a copper–nickel alloy heating wire can provide a stable heat source and is suitable for electrical–thermal systems. The surface temperature reached a stable point at 38 °C after 240 min of heating using electrical energy. The recommended heating wire parameters were identified based on the snow-melting performance and energy consumption. The optimal heating wire spacing is 7.5 cm and the most energy-efficient heating wire power is 250 W/m2. The automatic snow-melting membrane roof is always free of snow if snow melting is started at the instant when the snow thickness is less than 20 mm and the solar irradiance is in the range of 100–250 W/m2. The ambient temperature contributes minimally to the snow-melting performance. Finally, artificial neural network (ANN) and multiple linear regression (MLR) models were built to predict the snow-melting performance using the aforementioned parameters as inputs. The ANN model can predict and evaluate the snow-melting performance trend more accurately than the MLR model. The results indicate the possibility for large-scale practical engineering applications of electrical–thermal systems for snow removal.

Modelling the impact of hailstones on flat steel roofing membranes for residential buildings

Metal roof panels are commonly used on residential and commercial buildings. Steel panels exposed to hail have not yet been adequately tested for dent resistance. A finite element model (FEM) was used to analyze the entire test setup. To compare artificial hailstones with natural hailstones, which remained intact after impact, different steel sheets were struck by different sizes of artificial hailstones at different terminal velocities. The simulation and the material properties are assessed by comparing the experimental results with the FE model. An equation to predict the dent depth based on kinetic energy and stress is also presented. The results of this study provide a better understanding of the failure modes of hail and roof panels and their effects on dent resistance. In this study, the results of observations and numerical simulations agreed well with those of analytical models. The result is that the proposed equation overestimates the dent depths compared to the dent depths obtained with finite element models, while the equation leads to an underestimation of the dent depths found in the steel sheets.

Experimental study of wind-induced dynamic response and collapse of a mechanically-attached membrane roofing system installed on metal substrate of flat-roofed low-rise steel building

This paper investigates the wind-induced dynamic response at design wind speed and the collapse of a mechanically-attached membrane roofing system installed on metal substrate of flat-roofed low-rise steel building, based on a wind pressure loading test using full-scale assembly specimens. Three kinds of waterproofing membranes with different mechanical properties are tested. The wind loads employed in the test are generated by using the time histories of wind pressure coefficients on the roof of a flat-roofed low-rise building with low parapets, which were obtained from a wind tunnel experiment. Both the temporal and spatial variations of wind pressures are reproduced by using three Pressure Loading Actuators (PLAs). A step-wise pressure loading test commonly employed in the conventional wind-resistant performance evaluation in Japan is also carried out for a comparative purpose. The results indicate that the fasteners connecting the disks with the metal substrate are subjected to not only vertical uplift forces due to negative wind pressures (suctions) but also horizontal forces related to the membrane deformation. The maximum value of horizontal force is nearly equal to that of the vertical force. Although the general correlation between vertical and horizontal forces is not so high, the maximum values of these forces may occur almost simultaneously. Larger the membrane deformation, larger the horizontal forces are. The horizontal forces reduce the failure loads and affect the failure modes significantly. Therefore, the effect of horizontal forces should be considered in the evaluation of wind-resistant performance of mechanically-attached membrane roofing systems. The failure load under step-wise pressure is generally smaller than that under fluctuating wind pressures. Therefore, the conventional step-wise pressure loading test can be used as a simple method for evaluating the failure load of the roofing system on the safer side.

Pilot-scale NO removal efficacy of photocatalytic roofing granules under urban environmental conditions

Photocatalytic building envelope materials harness sunlight to activate self-cleaning and de-polluting properties, which can help mitigate the urban heat island effect and abate urban pollution. The performance of roofing membranes manufactured with bright-white photocatalytic (BWP) granules, and with a non-photocatalytic bright-white control (BWC), were evaluated. The solar reflectance of unexposed specimens was 0.56 for BWP and 0.60 for BWC. Small changes in solar reflectance with respect to the initial values were observed during 22 months of field exposure between March 2020 and January 2022, indicating good resistance to soiling. Changes in the de-pollution capacity during the same period were quantified with a bench-scale method adapted from the ISO Standard 22197-1, in which unexposed and aged specimens were placed horizontally inside a flow chamber admitting clean air enriched with nitric oxide (NO) under UV irradiation. In addition, a pilot-scale approach was developed to evaluate the photocatalytic performance of the same materials under more realistic urban environmental conditions. An outdoor exposure chamber was designed and built with a rectangular stainless-steel main body topped with a UV-transparent fluorinated ethylene propylene (FEP) thin film. The area of the 30 cm × 90 cm BWP specimen tested in the outdoor chamber was more than one order of magnitude larger than those evaluated in the benchtop apparatus. The BWP membrane was pre-activated by field exposure for 75 days. The pilot-scale chamber operation was validated in the laboratory using UV lamps to irradiate the BWP membrane and a reference TiO 2 -coated aluminum plate (P25, 1 g m −2 ) of the same dimensions. Tests showed comparable or better performance of the BWP membrane with respect to the P25 film. Its de-pollution capacity was tested with direct sunlight irradiation in Berkeley, California (37.88° N, 122.25° W) during June 2020. Urban air was enriched with NO, or with a NO/NO 2 mixture, and circulated through the pilot-scale chamber at two different flows: 1.1 and 440 L min −1 . The gas phase concentrations of NO and NO 2 were measured upstream and downstream of the tested specimen with a chemiluminescence analyzer. Upstream levels of the challenge gases were high but realistic, not exceeding 200 ppb. The UV irradiance outdoors (15–30 W m −2 ) was higher and more variable than in indoor tests (11.5 W m −2 ), leading to overall higher NO deposition velocity under direct sunlight. In outdoor measurements, the NO deposition velocity increased at higher irradiances. When NO was the only challenge gas, a fraction of NO was oxidized to NO 2 resulting in lower NO and higher NO 2 downstream concentrations. However, when tested with NO/NO 2 mixtures, the concentration of both compounds decreased during irradiation, and the surface showed a faster loss of photoactivity for NO 2 , compared with NO. These effects are consistent with those observed in the laboratory. The NO x deposition velocity outdoors was 0.7 and 105 μmol h −1 m −2 for the low and high air flow, respectively. • The de-NO x performance of a photocatalytic roofing membrane was evaluated. • ISO Standard 22197-1 was used to determine NO x removal rates in bench tests. • Tested specimens were aged in the field over a 22-month period. • A flow exposure chamber was built for outdoor pilot-scale tests. • The NO deposition velocity increased with UV irradiance between 15 and 30 W m −2

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.

Estimation of wind-induced responses of large membrane roofs including the nonlinear motion-induced aerodynamic forces

The effects of nonlinear motion-induced aerodynamic forces on the dynamic responses of large-scale membrane roofs are studied. These forces are from the nonlinear aerodynamic damping and linear aerodynamic stiffness. The responses are analytically obtained using an equivalent nonlinear approach. The characteristics of these responses, including the root-mean-square response, kurtosis, probability density function, peak factor, and peak response are analyzed. The response time history of large-scale membrane roofs under strong wind loads obtained from the nonlinear equation of motion of the structure with the fourth-order Runge-Kutta method is compared with the analytical solution. The proposed analytical approach is shown accurate and effective. Results indicate that the vortex-induced vibration of the roof in the high reduced velocity range is greatly influenced by the negative aerodynamic damping. The dynamic responses in the low reduced velocity range are mainly influenced by the negative aerodynamic stiffness with general buffeting behaviors. The proposed approach will contribute to a more economical preliminary design of such structures under strong winds.

Durability and Degradation of PVC-P Roofing Membrane-Example of Dynamic Fatigue Testing.

This paper presents a study of PVC-P waterproofing membrane Specimens. The Specimens were taken from different segments of a flat roof after a service life of 11 years. The reason for analysing the condition of the Specimens was the apparent degradation of the waterproofing, which no longer guaranteed the watertightness of the roof. The analysis of the performance of the Specimens was based on the control of the mechanical properties, which were compared with the declared values. The mechanical properties of the degraded PVC-P waterproofing membranes with a polyester mesh backing, which are prescribed by the standards, do not usually deviate from the declared properties. This often poses a problem for liability and warranty claims due to the poor quality of the waterproofing membrane. There may be several causes of degradation of PVC-P. For this reason, in this paper, we present the possibility of controlling the properties of PVC-P waterproofing membranes using cyclic dynamic fatigue, microstructure analysis using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the cause of the deterioration of the PVC-P waterproofing membranes is often related to dehydrochlorination of the polymer. However, the deterioration of the mechanical properties of the PVC-P waterproofing membranes can be successfully demonstrated by cyclic dynamic fatigue.

Positive Aspects of Green Roof Reducing Energy Consumption in Winter

Greening structures attract worldwide attention because of their multidisciplinary benefits. Green roofs are considered one of the best ways to eliminate summer overheating, mitigate climate change, or reduce the urban heat island effect. The winter season and its impact on building energy consumption are often overlooked. Common standards do not take a green roof structure into consideration because of possible high water content in their layers. Additional roof layers may have a positive effect during the winter; they help reduce surface overcooling in cloudless winter nights. This paper analyses experimental measurements taken on two different extensive green roofs and compares the results with a single-ply roof (R) with a PVC membrane. Surface overcooling of the R due to radiation reaching up to 10 °C, whereas the green roof membrane is protected. The influence of thermal loss is not so important for the current climate in Central Europe, as the required U-values are lower than 0.1. The temperature difference is reduced from 17 °C on the membrane to 0.7 °C on the top of the concrete slab. The green roof is still advantageous, and the vegetation surface has better thermal stability. The advantage is clearly recognisable in the area of the condensation zone. The difference between these two extensive green roofs is very small in regard to the accuracy of the temperature sensors. The outcome showed the thermal loss reduction compared to the common flat roof; however, after analysis, it was more marginal than expected.

Characterization and Optimization of AZO Nanoparticles as Coatings for Flexible Substrates toward High IR Reflectivity.

Energy consumption by air-conditioning is expansive and leads to the emission of millions of tons of CO2 every year. A promising approach to circumvent this problem is the reflection of solar radiation: Rooms that would not heat up by irradiation will not need to be cooled down. Especially, transparent conductive metal oxides exhibit high infrared (IR) reflectivity and are commonly applied as low-emissivity coatings (low-e coatings). Indium tin oxide (ITO) coatings are the state-of-the-art application, though indium is a rare and expensive resource. This work demonstrates that aluminum-doped zinc oxide (AZO) can be a suitable alternative to ITO for IR-reflection applications. AZO synthesized here exhibits better emissivity to be used as roofing membrane coatings for buildings in comparison to commercially available ITO coatings. AZO particles forming the reflective coating are generated via solvothermal synthesis routes and obtain high conductivity and IR reflectivity without the need of any further post-thermal treatment. Different synthesis parameters were studied, and their effects on both conductive and optical properties of the AZO nanoparticles were evaluated. To this end, a series of characterization methods, especially 27Al-nuclear magnetic resonance spectroscopy (27Al-NMR) analysis, have been conducted for a deeper insight into the particles' structure to understand the differences in conductivity and optical properties. The optimized AZO nanoparticles were coated on flexible transparent textile-based roofing membranes and tested as low-e coatings. The membranes demonstrated higher thermal reflectance compared with commercial ITO materials with an emissivity value lowered by 16%.

The Benefit of Horizontal Photovoltaic Panels in Reducing Wind Loads on a Membrane Roofing System on a Flat Roof

The present paper proposes a measure for improving the wind-resistant performance of photovoltaic systems and mechanically attached single-ply membrane roofing systems installed on flat roofs by combining them together. Mechanically attached single-ply membrane roofing systems are often used in Japan. These roofing systems are often damaged by strong winds, because they are very sensitive to wind action. Recently, photovoltaic (PV) systems placed on flat roofs have become popular. They are also often damaged by strong winds directed onto the underside, which cause large wind forces onto the PV panels. For improving the wind resistance of these systems, we proposed to install PV panels horizontally with gaps between them. Such an installation may decrease the wind forces on the PV panels due to the pressure equalization effect as well as on the waterproofing membrane due to the shielding effect of the PV panels. This paper discusses the validity of such an idea. The pressure on the bottom surface of a PV panel, called the “layer pressure” here, was evaluated by a numerical simulation based on the unsteady Bernoulli equation. In the simulation, the time history of the external pressure coefficients, measured at many points on the roof in a wind tunnel, was employed. It was found that the wind forces, both on the PV panels and on the roofing system, were significantly reduced. The reduction was large near the roof’s corner, where large suction pressures were induced in oblique winds. Thus, the proposed method improved the wind resistance of both systems significantly.

Computational Wind Engineering of a Mast-supported Tensile Structure

The Computational Fluid Dynamics (CFD) analysis of wind actions on a cube and on the hyperbolic surface of a mast-supported tensile structure is presented. As standard in Computational Wind Engineering (CWE) the models were analyzed in incompressible fluid flow. For the CWE study, the Reynolds-Averaged Navier-Stokes (RANS) equations were solved with two of the most widely used turbulence models, Realizable k−ε and SST k−ω. The validation of the CWE models included the comparison of the numerically determined pressure coefficient fields with existing Wind Tunnel test (WT) results. The membrane forces and the displacements of the membrane roof were calculated by the Dynamic Relaxation Method (DRM), corresponding to the different (CWE and WT) pressure coefficient fields of the tensile roof. In addition to the pressure coefficients, the membrane force and the displacement fields and their significant values were also compared. It is presented that both turbulence models provide a suitable solution; the pressure coefficients and the membrane forces are also acceptable approaches to the experimental results.

Pitched unventilated wood frame roof with smart vapour barrier – field measurements

Unventilated wood-frame roofs may provide smaller roof thickness and less material use compared to conventional unventilated roofs with all the thermal insulation above the load bearing structure. Unventilated roofs are, however, normally built without wooden materials between the vapour barrier and roof membrane due to moisture safety. Field measurements on the pitched unventilated wood-frame roof of an office building in Norway is performed to demonstrate and document the performance of this type of roof construction. Through monitoring of moisture and temperature, the study aims to contribute to verification of simulations and laboratory measurements showing that unventilated wood-frame roofs may be built with wooden materials if a smart vapour barrier is used. The results show moisture levels below 15 weight-% on the warm side of the rafters throughout the first 15 months of measurements. On the cold side of the rafters, the moisture content increased during winter due to built-in moisture in the construction and reached levels close to 25 weight-%. The moisture content decreased to around 15 weight-% when summer arrived, which shows an expected redistribution of moisture and indicates possible drying of the construction. The measurements underline the importance of limiting built-in moisture to reduce the risk of mould growth, but the study also implies that for some given premises an unventilated pitched wood-frame roof may have acceptable moisture risk.

Thermal environment analysis of enclosed dome with double-layered PTFE fabric roof integrated with aerogel-glass wool insulation mats: On-site test and numerical simulation

To study the thermal performance of an enclosed dome with double-layered PTFE membrane with aerogel-glass wool insulation mats, a comprehensive on-site test was carried out. Twenty-two wireless thermometers were used to monitor the temperature of key positions during a clear to cloudy day in summer. Solar irradiance was recorded as well. A numerical model was established to compare the thermal insulation property of this case and other three cases with different thermal insulations for double-layered membrane roof containing no extra insulation, peripheral wool glass insulation and all aerogel insulation. These cases only differ in the occupation area of thermal insulation materials laid on inner membrane. On-site test illustrates that the novel roof with aerogel- glass wool insulation can effectively prevent ambient radiation to pass through and render the stands insusceptible to the sunlight in regardless of the incidence angle. The temperature field of the dome is stratified and temperature only varies in vertical direction. According to numerical analysis, the current roof performs best in terms of thermal insulation property. This roof with combined insulation can reduce the average temperature difference of outdoor and indoor space by 7.7 ℃ while the value is merely 7.0 ℃, 5.9 ℃ and 4.8 ℃ for under the same environment condition.

The Thermal Behaviour of a Cylindrical Air Layer Enclosed between Double Fabric Roof Membranes

The Thermal Behaviour of a Cylindrical Air Layer Enclosed between Double Fabric Roof Membranes

Wind-Induced Dynamic Behavior of Mechanically Attached Single-Ply Membrane Roofing Systems Installed on Flat Roofs

The present paper investigates the wind-induced dynamic behavior of a mechanically attached single-ply membrane roofing system installed on flat roofs of middle-rise and high-rise buildings with or without parapets. First, the wind pressure distributions on the roof were measured in a turbulent boundary layer. The results indicate that the parapets affect the wind pressure distributions significantly. Very large peak suctions are induced near the windward corner of the roof in an oblique wind in the case of a building without parapets. Then, we have developed a test method for evaluating the wind-resistant performance of the roofing system using three Pressure Loading Actuators (PLAs) and a chamber to which a full-scale specimen is attached. In the experiments, the chamber was divided into three spaces by using thin silicon sheets. The PLAs generated different fluctuating pressures in these spaces using the time history of wind pressure coefficients measured at three points near the windward corner of the roof in an oblique wind. We measured the membrane deformations and the wind forces acting on the fasteners connecting the membrane with the structural substrate. The results indicate that horizontal forces nearly equal to or larger than the vertical ones are generated on the fasteners, which may cause pulling out of fasters more easily. The failure mode was found to be different from that obtained from a ramped pressure loading test. We have also developed a model of finite element analysis, which was validated by an experiment. The results of analysis for a wide area of roofing system indicate that relatively large horizontal forces may be generated on the fasteners in the field region of the roof for buildings with parapets.

Shape dependence of wind pressure peak factor statistics in hyperbolic paraboloid roofs

The complex shape dependence of wind pressure’s peak factors (PFs) makes it difficult to predict their values for all geometries by using analytical models. Thus, experimental studies are necessary to validate available or new analytical models for each specific shape and geometry. Very little information is available in the literature for the hyperbolic paraboloid geometry, which is frequently used for cable net and membrane roofs that are particularly appropriate for covering large spans. This paper focuses on wind pressure’s PFs for this specific geometry. It presents a statistical analysis of experimental data taken from wind tunnel experiments on eight different geometries, obtained through the combinations of squared and rectangular plan shapes, high and low models, and two different curvatures of the roof parabolas. Roof zones for which a non-Gaussian behavior is predominant are identified. A comparison is made between PF statistics obtained experimentally and those estimated by the Davenport, modified Hermite, and Translated Peak Process (TPP) models, in terms of means and standard deviation errors estimated over the entire roofs. It is concluded that the modified Hermite and the TPP models provide the best estimates of the PF means and standard deviations, respectively.

Comparison of Leak Detection Methods Used for Testing Large Area Membrane Roofs for Durability Assessment Purposes

Abstract This article presents different types of commercially available roof waterproofing membrane systems used on roofs with large surface area. It deals with the causes of deterioration of such membranes due to environmental factors and describes the tests used to detect leaks and determination of the severity of deterioration of polymeric membranes taking into account the properties declared by their manufactures. The last part of the article is a case study comparing a brand new membrane with a membrane after 27 years in service.

Comparison of three explorative methods for identifying building surface materials contributing pollutants to stormwater

Runoff from building and structure surfaces may contribute to the pollution of urban stormwater and, thereby, to the degradation of the receiving water quality. Various micropollutants have been found in surface runoff from buildings in the urban environment, including metals and organic micropollutants. Effective methods for identification of such pollutants and their sources are the prerequisites for the development of control measures. In this paper, three different methods for the identification of building surface materials acting as sources of metals (Cd, Cr, Cu, Ni, Pb and Zn), nonylphenols and phthalates are presented: (i) screening of the material composition, (ii) laboratory leaching experiments with synthetic rainwater, and (iii) open-air pilot testing of material panels exposed to actual rainfall and runoff. These three methods cover a wide span of experimental aspects, including, e.g., size of material samples, resource demands, and control of influential factors. Nine materials commonly used on building and structure surfaces in the urban environment were tested: metal sheets of zinc, copper, galvanised steel, coated corrugated steel and stainless steel; and, four different roofing membranes of bitumen as well as polyvinyl chloride (PVC). The experimental results indicated that all three methods were meritorious in providing some information contributing to the identification of pollutant sources. The screening of material composition for targeted pollutants is relatively quick and inexpensive, but may fail to identify minor sources of pollutants, or may identify the substances present in the material, but not released in contact with water. Laboratory leaching was generally effective in identifying sources of substances present in surface runoff, but was unsuitable for estimating the magnitude of actual concentrations in building runoff. Open-air pilot studies of material samples (exposed area = 2 m2) were thought to provide the results corresponding well to concentrations in runoff from actual building surfaces, but required relatively large financial and labour resources. Thus, the choice of the method for pollutant identification should be based on study objectives, and some benefits may be achieved using more than one method in an integrated manner; e.g., composition screening and lab or open-air leaching of targeted materials.

Mean Operating Temperature (MOT) of Commercial Roof Assembly and Its Impact on the Energy Performance

In the thermal design of low sloped roofing assemblies, two parameters are overlooked, one is the surface temperature of the roof assemblies which provides the required temperature gradient for heat flow, and the other is the mean operating temperature of the roof assembly, which has direct implications on the thermal performance of the insulation. An in situ field study was conducted in collaboration with Alberta Roofing Contractors Association (ARCA) on their headquarters building located in Calgary, to generate data on the mean operating temperature of the roof assemblies and to determine whether the thermal design of roofing assemblies using conventional methods is an accurate portrayal of in-service thermal performance. For the present study, two roof assemblies insulated with polyisocyanurate insulation, one with a white reflective roof membrane and the other with the black membrane were selected and instrumented. During the monitoring period, the mean operating temperature (MOT) of the roof assembly whether it is calculated as the average of interior and exterior ambient (MOTAIR,) or the average of surface temperatures (MOTSurface), was found to be below 24 °C (75 °F), which opposes the current roof thermal designs that are being designed using label R-value (thermal resistance) of the insulation reported at the mean temperature of 24 °C (75 °F) rather than temperature-dependent thermal resistance. The comparison of two energy transfer theoretical models, QConvention and QMOT, with the measured data indicated that the conventional approach of roof thermal design underestimates the energy performance of the roof assembly on average by 30%. The use of roof surface temperatures and the corresponding temperature-dependent thermal resistance of the insulation as in QMOT has been demonstrated to improve predictions of the energy performance. In addition the loss in thermal resistance due to blowing agent diffusion in polyisocyanurate was evaluated after two years of in situ installation.

Experimental characterization of reflective coating material for cool roofs in hot, humid and dusty climate

Considerable energy is used for cooling buildings in hot climates like those found in Gulf Cooperation Council (GCC) countries. Designing building envelopes for the purpose of saving energy can necessarily help reduce the building's operating expenses and therefore energy demand over time. For roofing systems, a research project was recently conducted to assess experimentally and numerically the performance of the roofing systems. This paper presents the experimental results of this project. Cool/reflective/white roofs use reflective materials or coatings to reflect a portion of the incident solar radiation. This results in lowering the surface temperature of the cool roofs compared to black roofing systems. As such, cool roofs help reduce the cooling loads during the summer season. This paper presents the test results of characterizing the short-wave solar reflectivity of a reflective roofing material that can be used in cool roofs of Saudi buildings. A Reflective Coating Material (RCM) that is commercially available in the GCC markets was used in this study. Also, the reduction in the solar reflectivity due to dust and dirt accumulations on the surface of the RCM was investigated in this study when this coating was exposed to a dusty and polluted climate of Jubail Industrial City (JIC). As well, the effect of applying different cleaning operations on the solar reflectivity of the RCM was investigated. The test results showed that dust/dirt can significantly contribute in reducing the short-wave solar reflectivity of the RCM. For the RCM subjected to the natural weathering conditions at different exposures times, the results showed that a maximum enhancement of 5% in the short-wave solar reflectivity was achieved, as a result of conducting air plowing process that simulates the wind action. Additionally, a maximum enhancement of 45% in the short-wave solar reflectivity was achieved as results of conducting water cleaning/rinsing process that simulates the rain action and as well conducting washing with dishwashing detergent that simulates homemade cleaning. Furthermore, conducting professional cleaning has resulted in insignificant enhancement in the short-wave solar reflectivity compared to conducting homemade cleaning. Finally, this paper provides a test procedure for characterizing the dust concentration/intensity on the surface of the RCM at different exposure times to the natural and polluted climate. This test procedure can easily be applied on different types of reflective roofing materials and membranes that can be used in cool roofs.