Nuova ricerca

CHIARA FERRARI

CULTORE DELLA MATERIA
Dipartimento di Ingegneria "Enzo Ferrari"

Home |


Pubblicazioni

2021 - Standard test methods for rating of solar reflectance of built-up surfaces and potential use of satellite remote sensors [Articolo su rivista]
Costanzini, S.; Ferrari, C.; Despini, F.; Muscio, A.
abstract

More and more attention is being paid to the solar reflectance of built-up surfaces due to its influence on the summer heating of buildings and urban areas and the consequent effects on energy needs for air conditioning, as well as on the peak load of the electric grid. Several standard test methods are available for measuring solar reflectance in the laboratory or in the field, based on different devices and approaches. A convergence of some methods has been achieved by rating programs in the U.S. and, more recently, in Europe and other areas. However, laboratory or field measurements are impractical for characterizing a large number of urban surfaces—whether it is for identifying critical issues, developing policies, or verifying compliance with building requirements. In this regard, satellite remote sensors have recently become available, through which it is possible to estimate the reflectance of roof and pavement surfaces thanks to a spatial resolution that is suitable for identifying and characterizing individual built-up surfaces. In the present paper, the most-used standard test methods for rating of solar reflectance are reviewed. Subsequently, some publicly accessible satellite sensors are examined, through which comparable measurements could be obtained.

2021 - Urban surfaces analysis with remote sensing data for the evaluation of UHI mitigation scenarios [Articolo su rivista]
Despini, F.; Ferrari, C.; Santunione, G.; Tommasone, S.; Muscio, A.; Teggi, S.
abstract

Considering the new IPCC report and its recent suggestions, it is important to pay serious attention to the Urban Heat Island issue. In this study, satellite images acquired by the Worldview3 sensor (WV3) were processed to classify the different kinds of urban surface and to compute the albedo value for each surface. Then several UHI mitigation scenarios were analyzed, varying selectively the surface albedo by choosing solar reflective materials. Clay tile pitched roofs, dark roofs and parking areas were considered as “modifiable surfaces” and their albedo values were increased on the basis of the literature and of data made available by product manufacturers. For each proposed scenario, the reduction of intensity of the Urban Heat Island effect (ATD), the energy saving brought by lower absorption of air conditioning systems (ΔE) and the consequent cost savings were calculated. All the scenarios proved to be convenient and with a relatively fast return on investment. In particular, two scenarios involving the modification of several surfaces at the same time proved to be the most promising ones from the perspective of a public administration, with significant benefits on the well-being of the population, as well as with similar and relatively short payback periods.

2020 - Effects of soiling and weathering on the albedo of building envelope materials: Lessons learned from natural exposure in two European cities and tuning of a laboratory simulation practice [Articolo su rivista]
Paolini, R.; Terraneo, G.; Ferrari, C.; Sleiman, M.; Muscio, A.; Metrangolo, P.; Poli, T.; Destaillats, H.; Zinzi, M.; Levinson, R.
abstract

Chemical and physical stress, weathering, organic and inorganic matter deposition, and microbial growth over time, or “aging”, affect the optical-radiative performance of building envelope materials. Natural exposure helps to quantify these effects, but it usually requires several years. Further, the contribution of the different degradation agents cannot be isolated, and results from different campaigns cannot be easily compared because of the variability in the boundary conditions producing aging. Here we present an adaptation of the protocol implemented by ASTM as D7897-18 “Standard Practice for Laboratory Soiling and Weathering of Roofing Materials to Simulate Effects of Natural Exposure on Solar Reflectance and Thermal Emittance”. The aim is to reproduce in the laboratory the changes in albedo (solar reflectance) and thermal emittance experienced by building envelope materials in European urban areas rather than in the United States. We tuned the spraying duration and weathering cycles, and we compared the UV–vis–NIR reflectances of naturally-aged specimens (48 months in Rome and Milan) of roofing and wall finish materials to those exposed to laboratory weathering and soiling. Excluding those materials that show early physical-chemical degradation, the mean absolute deviation between natural and laboratory exposure of roofing products is equal to 0.027 in albedo. This is a lower value than the differences between two natural exposure campaigns at the same site. We clearly defined the limits of application of the protocol, providing an appraisal of the repeatability of natural aging. Moreover, we identified possible improvements in the methodology to conduct both natural and laboratory exposure.

2020 - On Bio-Deterioration of Solar Reflective Materials: An Innovative Experimental Procedure to Accelerate the Ageing Process of Surfaces [Relazione in Atti di Convegno]
Santunione, Giulia; Ferrari, Chiara; Muscio, Alberto; Sgarbi, Elisabetta
abstract

2019 - Accelerated biological ageing of solar reflective and aesthetically relevant building materials [Articolo su rivista]
Santunione, G.; Ferrari, C.; Siligardi, C.; Muscio, A.; Sgarbii, E.
abstract

The properties of building materials relevant to their thermal or aesthetical performance can be seriously influenced by the colonization of external surfaces by microorganisms. Deterioration phenomena due to biological aggression cause the loss of energy performance of solar reflective materials because of the decrease of solar reflectance. Bio-deterioration also affects cultural heritage, damaging the aesthetic appearance and thus the historic value. In order to investigate the consequences of biological aggression in short times, an accelerated test method based on a laboratory-reproducible set-up is proposed. Specific and controlled environmental conditions are chosen to accelerate as much as possible biological growth on building materials. In this regard, a reproducible bio-ageing protocol has been outlined and it allows a set of materials to reach an advanced bio-aged level in a short time (8 weeks or less). This test method is aimed to comparatively evaluate different materials under a given set of ageing conditions. Through surface, microstructural and chemical analysis, the evolution of the materials’ properties after ageing is investigated. Attention is also paid to bacterial and algal growth rate by analysing time-progressive images.

2019 - Smart use of mechanical ventilation for energy retrofit of residential dwellings [Relazione in Atti di Convegno]
Pedrazzi, S.; Ferrari, C.; Allesina, G.; Muscio, A.
abstract

Residential buildings of Italy built during the last century usually show very poor energy performance. The only retrofit action widely implemented on their envelope is substitution of windows. These are very seldom coupled with mechanical ventilation, however, so their high air tightness induces serious problems of moisture condensation and mold formation-unless they are left open and their usefulness nullified. In this work, a smart combination is simulated of single flow mechanical ventilation, in itself essential to control indoor air quality and ventilation heat loss, with a relatively inexpensive sunspace built on an existing balcony, aimed to behave as a preheating chamber of the inlet cold air in winter. Moreover, mechanical ventilation is combined with an electric heat pump for hot water production, in which the outlet air flow of warm exhaust air is introduced to improve the coefficient of performance of the heat pump in the cold seasons. Energy savings allowed by such smart yet simple combination of existing technologies are discussed.

2019 - Ventilated pitched roof with forced ventilation and flow homogenizer device: Testing and performance assessment [Relazione in Atti di Convegno]
Ferrari, C.; Muscio, A.
abstract

Ventilated tile roofs are common objects in the construction sector of Italy. A preferred type is characterized by a ventilated air space between the upper tile layer and the roof structure below. The air enters through openings at the gutters level, flows up below sheathing in the air space along the pitch and is finally discharged through openings along the ridge. This setup, which leaves the room below the roof sealed and habitable, allows removing the heat brought by the absorbed solar radiation thanks to the flow that is established by natural ventilation in the air space. However, its actual performance is often weak and also unpredictable due to continuously changing buoyancy forces. Nonetheless, a permanent and adequate flow can be ensured even through a relatively thin air space and for whichever irradiance and wind conditions by forced ventilation: a properly designed fan can provide the desired flow rate by extracting the air after this is collected along the ridge by a manifold. A thorough design and manufacturing of the manifold is needed, however, to avoid a highly inhomogeneous flow, which would follow the easiest path and leave most of the pitch practically unventilated. As an alternative, a throttling shutter parallel to the ridge has been proposed to progressively choke the flow entering the manifold through parallel climbing ducts as the fan is approached, possibly allowing onsite adjustment after installation. In this work the solution, developed by means of a small scale test bed, is illustrated in details and some methods to assess the performance are presented.

2018 - On field evaluation of solar reflectance: how the 1918A masks affect the albedo measurements [Relazione in Atti di Convegno]
Santunione, Giulia; Ferrari, Chiara; Muscio, Alberto
abstract

2017 - How accelerated biological aging can affect solar reflective polymeric based building materials [Relazione in Atti di Convegno]
Ferrari, C.; Santunione, G.; Libbra, A.; Muscio, A.; Sgarbi, E.
abstract

Among the main issues concerning building materials, in particular outdoor ones, one can identify the colonization by microorganisms referred to as biological aggression. This can affect not only the aesthetical aspect but also the thermal performance of solar reflective materials. In order to improve the reliability of tests aimed to assess the resistance to biological aggression and contextually reduce the test duration, an accelerated test method has been developed. It is based on a lab reproducible setup where specific and controlled environmental and boundary conditions are imposed to accelerate as much as possible biological growth on building materials. Due to their widespread use, polymeric materials have been selected for the present analysis, in the aim of reaching an advanced bio-aged level in a relatively short time (8 weeks or less) and at the same time comparatively evaluate different materials under a given set of ageing conditions. Surface properties before, during and after ageing have been investigated by surface, microstructural and chemical analyses, as well as by examination of time progressive images to assess bacterial and algal growth rate.

2017 - MISURA E OTTIMIZZAZIONE DELLA RIFLETTANZA SOLARE DI TETTI VERDI [Relazione in Atti di Convegno]
Santunione, Giulia; Ferrari, Chiara; Libbra, Antonio; Sgarbi, Elisabetta; Muscio, Alberto
abstract

Tra le diverse soluzioni finalizzate alla sostenibilità ambientale e al contenimento del fabbisogno energetico estivo degli edifici vi sono i cosiddetti green roof, o tetti verdi. La loro efficacia dipende dalla tipologia di vegetazione che li costituisce, in relazione alla quale esistono ampie le possibilità di ottimizzazione in virtù della vastissima biodiversità vegetale disponibile. In questo lavoro, con l’intento di migliorare l’efficienza energetica dei tetti verdi attraverso l’aumento della loro albedo, si sono analizzate sperimentalmente le proprietà radiative di una specie erbacea con elevate potenzialità, la Stachys byzantina

2017 - Methods and instrumentation to measure the effective solar reflectance of fluorescent cool surfaces [Articolo su rivista]
Levinson, Ronnen; Chen, Sharon; Ferrari, Chiara; Berdahl, Paul; Slack, Jonathan
abstract

Fluorescent cool dark surfaces stay cool in the sun by reflecting near-infrared (NIR) radiation and by actively re-emitting in the NIR spectrum some of the energy absorbed from visible sunlight. The fraction of incident solar energy rejected by reflection and fluorescence is the “effective solar reflectance”, or ESR, of the surface. It is challenging to measure ESR with a solar spectrometer or a solar reflectometer, the radiometric instruments most commonly used to measure the solar reflectance (SR) of specimens in the laboratory. We have tested a variety of calorimetric techniques for using temperature in the sun to interpolate the effective solar absorptance (1 − ESR) of a fluorescent test specimen from the known solar absorptances of non-fluorescent reference specimens. Our experiments show that averaging out noise in the temperature signal induced by variations in convection is key. We developed a computer-controlled rotary apparatus that compares the temperatures in the sun of up to six specimens. Trials on six different fluorescent specimens indicate that it can measure ESR with a repeatability of about 0.02. To maximize the ratio of signal to noise in temperature determination, and to facilitate calculation of the fluorescence benefit (ESR − SR), measurements should be performed with specimens facing the sun.

2017 - On a solar reflective ceramic based glaze for asphalt shingle [Articolo su rivista]
Ferrari, Chiara; Mugoni, Consuelo; Montorsi, Monia; Siligardi, Cristina; Ferrari, Chiara
abstract

Solar reflective materials are one of the most effective solutions to counteract Urban Heat Island effect. Among them, asphalt shingles are one of the most widely used products. To improve solar reflectance of these surfaces usually both polymeric paint on the final product or ceramic glazes applied directly on the granules surface through rotary kiln are used. In this study the Design of Experiment approach is applied to an industrial formulation for ceramic glaze for asphalt shingles in order to find the optimal combination between pigment (Rutile and Talc), liquid phase (Sodium Silicate and Water) and heat treatment (700 °C −1100 °C). On the most significant samples, moreover, XRD and ESEM characterization has been performed in order to better understand the behaviour of the studied system. Interesting values in Solar reflectance were obtained, reaching ρsol=0.882 creating a good solar reflective product ready to be applied, through rotary kiln, on mineral granules for asphalt shingles.

2016 - A composite cool colored tile for sloped roofs with high 'equivalent' solar reflectance [Articolo su rivista]
Ferrari, Chiara; Libbra, Antonio; Cernuschi, Federico Maria; De Maria, Letizia; Marchionna, Stefano; Barozzi, Matteo; Siligardi, Cristina; Muscio, Alberto
abstract

Mediterranean cities are characterized by sloped roofs with ceramic tiles of traditional colors such as brick red in different tones. Their solar reflectance is generally low and can cause overheating of the building due to solar gains during the hot season. In this work, an innovative approach is tested to achieve roof tiles with high capacity of rejecting solar radiation. It consists of using a cool-colored tile with relatively high solar reflectance, combined with a thin insulating layer attached below the tile and made of a silica-gel super-insulating material. An aluminum foil with very low thermal emittance is also applied below the insulating layer. Along the perimeter of each tile, line brushes are attached in order to enclose an almost sealed air space between the aluminum foil and the roof slab below when the tiles are supported on wooden battens. Composite tiles like that outlined here can provide a strong increase of roof thermal resistance, helpful to control either heat loss in winter, or building overheating in summer. They can be installed onto an existing roof, for instance the sloped tile roof of a historical or traditional building, with no need to modify the roof height and structure.

2016 - Correlation between remote sensing data and ground based measurements for solar reflectance retrieving [Articolo su rivista]
Despini, Francesca; Ferrari, Chiara; Bigi, Alessandro; Libbra, Antonio; Teggi, Sergio; Muscio, Alberto; Ghermandi, Grazia
abstract

Surface and atmospheric modifications due to urbanization generally lead to the urban heat island effect (UHI). This phenomenon is an issue of growing interest and has long been studied by ground based observation. With the advent of remote sensing technologies, observation of UHIs became possible with airborne and spaceborne sensors. Remote sensing data allow urban surfaces characterization to study UHI mitigation methodologies such as the application of cool roofs and cool colors. In this study remote sensing data have been used first to identify urban surfaces and then to retrieve the solar reflectance value of these surfaces. The first area of interest is the city of Modena in the Emilia Romagna region (Italy). On this area orthorectified images by an airborne sensor are used. Available images do not allow to directly obtain the solar reflectance value. Therefore it has been investigated a correlation between satellite remote sensing data and ground based measurements. The solar reflectance was obtained for all urban surfaces of interest such as roofs and pavements. In this way it was possible to assess the real situation and to hypothesize achievable improvements in the solar reflectance of several urban surfaces aimed at improving thermal comfort and energy efficiency of buildings.

2016 - Development of a Solar-reflective Ceramic Tile Ready for Industrialization [Relazione in Atti di Convegno]
Ferrari, Chiara; Muscio, Alberto; Siligardi, Cristina
abstract

Solar-reflective surfaces represent an effective countermeasure to UHI. The market of "cool" materials is dominated by polymeric solutions which, under UV exposure, are damaged. On the other hand, an increasing attention was paid recently to ceramic-based solar-reflective surfaces, characterized by very long lifespan. A ceramic tile is typically made by a three layers structure: substrate-engobe-glaze. This structure has been exploited to develop a cool ceramic tile that can be produced in the same production facilities of common products to create a whole tile by merging technological results and industrial production needs, to achieve a compromise between performance and costs.

2016 - Robotic implementation of the slide method for measurement of the thermal emissivity of building elements [Articolo su rivista]
Pini, Fabio; Ferrari, Chiara; Libbra, Antonio; Leali, Francesco; Muscio, Alberto
abstract

A significant interest exists in measuring the thermal emissivity of building surfaces since high values combined with high solar reflectance allow rejecting solar energy absorbed by irradiated surfaces, whereas intermediate or low values permit to limit condensation of humidity, heat loss to the sky, or heat transfer through airspaces. The most used measurement method is probably that described by the ASTM C1371 Standard, which correlates the thermal emissivity to the radiative heat flux exchanged in the infrared between the sample surface, kept at ambient temperature, and the bottom surface of a hot emissometer head. With samples showing a low thermal conductivity, the 'slide method' modification is generally used: the hot head is allowed to slide above the sample in order to prevent this from warming up. The slide movement, however, is carried out by hand and time is needed to achieve a stabilized output, therefore the measurement may be time-consuming and also affected by the operator. In order to solve both problems, an automated approach is proposed here, in which the head is moved by the arm of a robot. This manages either the slide movement or the calibration with reference samples, interacting with a computerized data acquisition system that monitors the emissometer output.

2016 - Un nuovo approccio per lo studio del deterioramento delle proprietà superficiali: l’invecchiamento biologico accelerato [Relazione in Atti di Convegno]
Santunione, Giulia; Ferrari, Chiara; Libbra, Antonio; Sgarbi, Elisabetta; Siligardi, Cristina; Muscio, Alberto
abstract

La colonizzazione delle superfici esterne da parte dei microorganismi, può influenzare seriamente le proprietà dei materiali edili. Il fenomeno del deterioramento, dovuto all’aggressione biologica causa infatti perdita nelle performance energetiche dei materiali “cool” a causa di un decadimento della riflettanza solare. Inoltre, i problemi relativi al bio-deterioramento affligono anche i monumenti del patrimonio artistico, danneggiando sia il loro valore estetico, sia il loro valoro storico-culturale. Al fine di investigare quali sono le conseguenze dell’aggressione biologica sui materiali edili in tempi ristretti, questo lavoro mostra un metodo di prova di invecchiamento accelerato e riproducibile in laboratorio. Sono state accuratamente scelte specifiche condizioni ambientali per accelerare il più possibile la crescita biologica sui materiali. È stato messo a punto un protocollo di invecchiamento biologico ben dettagliato e riproducibile al fine di ottenere un buon livello di aggressione biologica ai set di materiali selezionati in un breve lasso di tempo (8 settimane). Si è volute inoltre testare tramite lo stesso protocollo di bio-deterioramento accelerato, l’efficacia dell’azione protettiva di alcuni prodotti alghicidi in commercio. Tale metodo permette di valutare e confrontare le performance di diversi materiali sottoposti alle medesime condizioni ambientali. Grazie alle caratterizzazioni delle superfici questo studio definisce come le proprietà dei materiali cambiano nel post invecchiamento attraverso analisi chimiche fisiche e strutturali, la crescita algale è stata inoltre monitorata attraverso periodiche acquisizioni di immagini analizzate con software specifici.

2015 - Design of a cool color glaze for solar reflective tile application [Articolo su rivista]
Ferrari, C.; Muscio, Alberto; Siligardi, Cristina; Manfredini, Tiziano
abstract

Solar reflective materials, so called cool roofs, can be identified as one of the most promising solutions to counteract urban heat island. Cool roof market is nowadays dominated by polymeric product, which can ensure good optical properties but poor durability against weathering and ageing. Ceramic-based products can be an excellent solution combining both good solar properties and higher durability against time, in particular if glazed. Embedded colored pigments, moreover, can help the introduction of these materials in Mediterranean building policies. These cool colored ceramic-based products, in fact, match naturally high thermal emissivity (ε=0.90) with higher mechanical, chemical and physical durability. A traditionally engobed porcelain stoneware tile was used as a substrate for a new generation of colored glazes characterized by different surfaces reaching promising values in solar reflectance.

2015 - Review on the Influence of Biological Deterioration on the Surface Properties of Building Materials: Organisms, Materials, and Methods [Articolo su rivista]
Ferrari, Chiara; Santunione, Giulia; Libbra, Antonio; Muscio, Alberto; Sgarbi, Elisabetta; Siligardi, Cristina; Barozzi, Giovanni Sebastiano
abstract

A strong attention is recently paid to surface properties of building materials as these allows controlling solar gains of the building envelope and overheating of buildings and urban areas. In this regard, deterioration phenomena due to biological aggression can quickly damage solar-reflecting roof surfaces and thus increase sharply solar gains, discomfort, air-conditioning costs and waterproofing degradation. The same deterioration problem has deleterious effect on cultural heritage, ruining its huge historic and artistic value. This work is aimed at providing an overview on the different organisms that affect the surface of most used building materials, to support the design of new building materials with long-lasting surface properties and to find a way to preserve cultural heritage. Artificial ageing is the long-term aim of this investigation, in which what in nature happens after months or years is compressed in a very short time by forcing the growth of microorganisms through a strict control on the different conditioning factors. Both natural and artificial ageing are eventually outlined in the last part of this work to provide a comprehensive idea of what is necessary to study in a complete way biological ageing protocols on building materials. Several characterization techniques are also introduced to analyse the influence of microorganisms on the surface of different building materials.

2014 - Effect of aging processes on solar reflectivity of clay roof tiles [Articolo su rivista]
Ferrari, Chiara; A., Gholizadeh Touchaei; M., Sleiman; Libbra, Antonio; Muscio, Alberto; Siligardi, Cristina; H., Akbari
abstract

Clay roof tiles are widely used as roofing materials because of their good mechanical and esthetical properties. The exposure to atmospheric agents and, most of all, to pollutants and smog affects negatively the solar reflectance of a tile surface. The aim of this study is to analyze the influence of aging on the solar reflectance of clay roof tiles. We studied samples provided by manufacturer in Greece and USA. Samples were coated with either organic or inorganic coatings. Natural aging processes were used for samples with inorganic coating, and artificial aging simulation was performed on all samples. Samples were naturally aged in a test farm in Arizona, with an exposure time of three years. In artificial aging processes, the surface of the tiles was subjected to the application of two different mixtures simulating exposure to (i) Arizona weathering agents such as clay, salts and soot and (ii) Arizona, Florida and Ohio weathering agents through an average mixture made by clay, salts, particulate organic matter and soot. The amount of soiling mixture deposited on the surface of the samples was aimed at reproducing a three-year exposure. Soiled samples were subjected to air blowing and rinsing under running water to simulate the wind and rain effects, respectively. The effects of both natural aging and artificial soiling on the surface reflectivity of the clay roof tiles were assessed in the ultraviolet–visible–near infrared range (range from 300 to 2500 nm). The two different soiling conditions were found to affect significantly the solar reflectance of the samples, in particular the samples soiled with the average mixture present a decrease up to 0.20, while Arizona weathering condition affects the solar reflectance up to 0.05, and neither air blowing nor rinsing seem to permit a significant recovery of the surface properties. All solar reflectance measurements were computed by averaging the spectral reflectivity weighted by the air-mass 1 global horizontal solar spectral irradiance.

2014 - Isola di calore e surriscaldamento estivo: cool colors in laterizio [Articolo su rivista]
Ferrari, Chiara; A., Libbra; Muscio, Alberto; Siligardi, Cristina
abstract

La riflettanza solare delle coperture varia a seconda del tempo e del luogo di esposizione ed è influenzata dai fenomeni naturali. I manti in laterizio si dimostrano un eccellente candidato, in funzione dell’edilizia ad alta efficienza energetica, sia per il contrasto dell’isola di calore urbana che per comfort indoor e la limitazione dei consumi estivi

2013 - Design of ceramic tiles with highsolar reflectance through the development of a functional engobe [Articolo su rivista]
Ferrari, Chiara; Libbra, Antonio; Muscio, Alberto; Siligardi, Cristina
abstract

Roofing solutions with high capacity to reflect incident solar radiation, the so-called cool roofs, can provide an effective answer to summer overheating of either individual buildings or whole urban areas. Nowadays, commercial cool roofs products are mainly represented by organic membranes and coatings, but ceramic tiles can represent an interesting alternative or complement in view of their low maintenance cost. In this work, it is illustrated how a high reflectance engobe can affect in a positive way the solar reflectance of a glazed tile thanks to the introduction of suitable raw materials and pigments. The reflectance was in fact found to be affected by either the support, the mineralogical composition, the engobe thickness or the glaze. The procedure through which the glazed tile is developed and tested is discussed, in the perspective of production through commonly used industrial processes.

2013 - Effect of ageing processes on solar reflectivity of clay roof tiles [Relazione in Atti di Convegno]
Ferrari, Chiara; A. G., Touchaei; M., Sleiman; Libbra, Antonio; Muscio, Alberto; Siligardi, Cristina; H., Akbari
abstract

Clay roof tiles are widely used as roofing materials because of their good mechanical and aesthetical properties. The exposure to atmospheric agents and, most of all, to pollutants and smog affects negatively the solar reflectance of atile surface. The aim of this study is toanalyzethe influence of ageing on the solar reflectance of clay roof tiles. We studied samples provided by manufacturer in Greece and USA. Samples were coated with either organic or inorganic based coating. Natural ageing processes were used for samples with inorganic coating, and artificial ageing simulation was performed on all samples. Samples were naturally aged in a test farm in Arizona, with an exposure time of 3 years. In artificial ageing processes, the surface of the tiles was subjected to the application of two different mixtures simulating exposure to i) Arizona weathering agents such as clay, salts and soot and ii) Arizona, Florida and Ohio weathering agents through an average mixture made by clay, salts, particulate organic matter and soot. The amount of soiling mixture deposited on the surface of the samples was aimed at reproducing a 3 years exposure. Soiled samples were subjected to air blowing and rinsing under running water to simulate the wind and rain effects, respectively. The effects of both natural ageing and artificial soiling on the surface reflectivity of the clay roof tiles were assessed in the UV-Vis-NIR range (range from 300 to 2500 nm). The two different soiling conditions were found to affect significantly the solar reflectance of the samples, in particularthe samples soiled with the average mixture present a decrease up to 0.20, while Arizona weathering condition affects the solar reflectance up to 0.05, and neither air blowing nor rinsing seem to permit a significant recovery of the surface properties. All solar reflectance measurements were computed by averaging the spectral reflectivity weighted by the AM1GH solar spectral irradiance.

2013 - Influence of the irradiance spectrum on solar reflectance measurements [Articolo su rivista]
Ferrari, Chiara; Libbra, Antonio; Muscio, Alberto; Siligardi, Cristina
abstract

Solar reflectance (SR) is the key performance parameter of cool roof and cool pavement materials. For its assessment, the measured spectral reflectivity of the sample is weighted by a reference spectrum of solar irradiance. Several standard and non-standard spectra are, however, available, taking into account different climate conditions, angle of incidence of the solar beam, and the contribution of the diffuse radiation content. This study is aimed at investigating the impact of using different solar irradiance spectra as specified by existing standards or suggested by qualified research institutions, and verifying if those spectra can yield equivalent SR values from the viewpoint of assessment of standard performance and comparison of commercial products. Several actual material are considered, either white or coloured ones and with assorted spectral behaviour.

2013 - Influence of the solar irradiance spectrum on solar reflectance measuremens [Relazione in Atti di Convegno]
Ferrari, Chiara; Libbra, Antonio; Muscio, Alberto; Siligardi, Cristina
abstract

Solar reflectance is the key performance parameter of cool roof and cool pavement materials. For its assessment, the measured spectral reflectivity of the sample is weighted by a reference spectrum of solar irradiance. Several standard and non-standard spectra are however available, taking into account different climate conditions, angle of incidence of the solar beam, contribution of the diffuse radiation content. This study is aimed at investigating the impact of using different solar irradiance spectra as specified by existing standards or suggested by qualified research institutions, and verifying if those spectra can yield equivalent solar reflectance values from the viewpoint of assessment of standard performance and comparison of commercial products. Several actual material are considered, either white or coloured ones and with assorted spectral behaviour.

2013 - Interlaboratory comparison of cool roofing material measurement methods [Relazione in Atti di Convegno]
A., Synnefa; A., Pantazaras; M., Santamouris; E., Bozonnet2; M., Doya; M., Zinzi; Muscio, Alberto; Libbra, Antonio; Ferrari, Chiara; V., Coccia; F., Rossi; D., Kolokotsa
abstract

The present study aims at investigating different methodologies and standards for measuring and calculating solar reflectance and infrared emittance, the two main properties characterizing cool roofing materials. In order to achieve this goal, an interlaboratory comparison testing has been set up among several laboratories that are members of the European Cool Roofs Council. The measurement methods practiced by the labs include measurement of the reflectivity by using spectrophotometers equipped with integrating spheres and reflectometers and measurement of the emissivity using different emissometer devices and FTIR spectrometers equipped with integrating spheres. Seventeen different samples representing the range of commercially available roofing materials and covering the full range of reflectance and emittance values have been selected and tested. The results of this study provide information on the suitability of the various methods to be used for cool roof products assessment. This work could potentially lead to the adoption of a European Cool Roof Standard.