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This paper describes a study aimed at providing outdoor illuminance data in Italy, to be used to evaluate daylight potential contribution in the energy performance of buildings. Starting from solar radiation data, a luminous efficacy model was implemented to derive outdoor illuminance for Italian territory. The results obtained were compared with ground measurements, carried out in three different Italian sites (Milan, Rome and Lampedusa island), and the accuracy of model, has been improved introducing specific metrics for Italian context. Typical Meteorological Years (TMYs) of global and diffused components of daylight illuminance, were built for 243 locations, considering different time profiles. Since the definition of the spatial and temporal trend of environmental variables or metrics requires the application of appropriate interpolation procedure, geostatistic methods (kriging), was used to develop Italian daylight maps. The daylight availability maps will be included in the Italian database of solar radiation (www.solaritaly.enea.it) providing an useful tool for lighting energy performances in buildings applications.

Artificial lighting has a relevant impact on the electricity uses in not residential buildings. The method to assess such uses is based on standards, which hardly take into account the daylighting contribution and the time evolution of the outdoor illuminance conditions. Different models were adopted to build diffuse illuminance reference years, starting from satellite images. These models lead to different daylight availability during the year. The paper explores the impact that these models have on the artificial lighting energy uses by hourly monthly mean calculations. The test was carried out with a climate based method, which takes into account: the outdoor luminous environment, the reference indoor visual task and the building daylight characteristics. A typical office building was used for the test in Rome, Italy. Results allowed to compare the impact of each model and to select the most suitable one to be implemented in the climate based method to predict artificial lighting use in buildings. © 2017 The Authors. Published by Elsevier Ltd.

Urban greenery is a natural solution to cool cities and provide comfort, clean air and significant social, health and economic benefits. This paper aims to present the latest progress on the field of greenery urban mitigation techniques including aspects related to the theoretical and experimental assessment of the greenery cooling potential, the impact on urban vegetation on energy, health and comfort and the acquired knowledge on the best integration of the various types of greenery in the urban frame. Also to present the recent knowledge on the impact of climate change on the cooling performance of urban vegetation and investigate and analyse possible technological solutions to face the impact of high ambient temperatures. © 2018 The Author(s).

Adaptive transparent building envelope technologies could play a significant role in decreasing energy use in buildings and providing a more comfortable indoor environment. In order to evaluate these potentials in an economic and accurate manner, it is essential to have numerical models and simulation tools which correctly reproduce the behaviour of such components at the building level. This paper presents and discusses the empirical validation of models for thermo- Tropic glazing, a specific adaptive transparent glazing, by means of a whole building performance simulation tool, EnergyPlus. Moreover, this study highlights the differences between two modelling approaches (EnergyPlus built-in and EMS models) and experimental data. Negligible differences are noted between the two modelling approaches, even though the models do not completely agree with experimental data unless a model calibration is performed. The EMS modelling approach could be successfully extended to other dynamic glazing technologies that do not have a builtin model available in EnergyPlus, provided that an accurate thermo.

Increase of the ambient air temperature in cities caused by the urban heat island phenomenon has a seri- ous impact on the economic and social system of cities. to counterbalance the consequences of the increased urban temperatures important research has been carried out resulting in the development of efficient mitigation technologies. the present paper aims to present the state of the art in terms of local climate change and urban heat island mitigation techniques. In particular, developments in the field on highly reflective materials, cool and green roofs, cool pavements, urban green and of other mitigation technologies are presented in detail, while examples of implemented projects are given. © 2016 Vilnius Gediminas Technical University (VGTU) Press.

Los materiales fríos se caracterizan por una alta reflectancia solar obtenida por el uso de colores claros o con productos de vanguardia de colores más oscuros pero de elevada reflectancia. Estos materiales pueden ser utilizados para la envoltura del edificio, en particular para techos, sino también como recubrimiento para las superficies del tejido urbano. Dada la alta reflectancia solar y la alta emisividad infrarroja, son capaces de permanecer frescos bajo la radiación solar manteniendo la temperatura superficial inferior a los materiales de construcción habituales. La consecuencia es una reducción del flujo de calor transmitido en el interior en caso de aplicaciones de construcción y la reducción del calor transferido al aire exterior por convección en el caso de aplicaciones en estructuras urbanas. En ambos casos, los materiales fríos son una estrategia importante para mitigar dos fenómenos surgido en el pasado que afectan sobre la energía y la calidad medioambiental de las ciudades con climas templados: el aumento del consumo de energía para enfriar los edificios y el efecto isla de calor. Los techos frìos han sido estudiados y comprobados en los últimos años y ahora se consideran como una tecnología madura y eficaz para muchos tipos de edificios y en diferentes climas. Mejorías significativas también se consiguieron para materiales fríos en aplicaciones urbanas; aunque algunos productos están disponibles comercialmente siguen siendo despreciables en el mercado. La primera parte de este documento está dedicada a la caracterización y evaluación de un nuevo producto utilizado en la pavimentación de carreteras y calles peatones. El producto tiene como base el hormigón poroso en lugar del asfalto porque ha una potencia más alta de reflexión. La segunda parte está dedicada al estudio del clima urbano cuando las superficies oscuras son reemplazadas por soluciones técnicas con un albedo más alto. Por fin, el artículo describe las intervenciones futuras de planificar para mejorar las características de los productos objeto de este estudio. Cool materials are characterised by high solar reflectance, achieved by the use of white and light colours or by advanced products with darker colours but high near infrared reflectance. These materials can be used for the building envelope, in particular for roofs, but also as coating for the surfaces of urban texture. Due to the high solar reflectance and the high infrared emissivity, they are able to remain cool under the solar radiation, keeping the surface temperature lower than usual construction materials. The consequence is the reduction of the heat flux transmitted to the indoor in case of building applications and the reduction of the heat released to the outdoor air by convection in case of urban texture applications. In both cases, cool materials are an important strategy to mitigate two serious phenomena emerged with emphasis in the recent past, which affect the energy and environmental quality of cities in temperate climates: the increase of energy consumption for cooling down buildings and the urban heat island effect. Cool roof have been studied and tested in the past years and now they are considered as a mature and efficient technology for many building categories in different climates. Significant improvements were also achieved for cool materials in urban applications, even if few products are commercially available and the market penetration is still negligible. The first part of this paper is dedicated to the characterisation and the assessment of a new product used for road and pedestrian pavements. The product is based on concrete instead of asphalt, which has a higher reflection power of the former. The porosity of the structure gives the product high drain performance, which is a crucial issue for the safety of urban pavements. The solar reflectance of the product was measured with an advanced optical facility for several product configurations: colour of the binder and the dimension of the grains. Spectral measurements were carried out for the whole solar range and luminous and NIR reflectance values were calculated as well.

The diffusion of TiO2-modified building materials has been constantly growing, especially in European countries, as attested by the number of publications, patents and international projects, with the aim of developing a suitable technology to oppose the increase in atmospheric pollution and the current depletion of natural resources. The work here presented focuses on the characterization of a self-cleaning and photocatalytic system for building façades, aimed at improving the optical performance and the aesthetics over time of urban surfaces and the surrounding air quality, as well as decreasing energy consumption for cooling in summer season. In facts, TiO 2-containing photoactive materials represent an appealing way to create self-cleaning surfaces, thus limiting maintenance costs, and to promote the degradation of polluting agents.

Energy saving in the building sector is one of the key issue to achieve environmental targets at national and EU levels. Even if characterised by a large number of different climatic conditions, Italy energy policies were aimed at reducing the energy consumption related to space heating in buildings, neglecting other relevant energy uses as space cooling, which has dramatically increased in the past years. The recent EU Directive for the State Members is to assess the energy quality of buildings taking into account all the relevant energy uses. Cool roofs are an old concept merged with new technologies that play a crucial role in the energy balance of buildings especially at Mediterranean latitudes. Reducing the solar gains thanks to the roof high solar reflectance, cool roofs keep the building cooler during cooling season, reducing the cooling demand and increasing the thermal comfort; On the other hand this technology has a negative impact on the winter energy balance. It is be noted that the performance of the roof surface also depends on the thermal emissivity, that drives the radiative exchanges of the roof towards the sky and the surrounding objects. If the performance of the cool roof products is a function of the above cited quantities, the technology impact is a function of several other parameters: climatic conditions, building geometry, thermo-physical characteristics of the building envelope. Energy rating and labelling are a quick solution to compare energy related products, as inferred from recent EU Ecodesign Directive which requires the energy labelling not only for products that consume energy but also for energy related components, as windows. This study presents the first studies aimed at the definition of an energy rating scheme for cool roof, starting from product properties and reaching the building performances, with a focus on dwellings. The methodology is based on a wide number of energy simulations carried out with an accurate dynamic calculation tools. The variables taken into account are: • Roof surface radiative properties; • Reference buildings characteristics - including solar and thermal properties, geometry, orientation; • Climatic zones: The calculations were carried out for Palermo, Rome and Perugia in order to take into account a wide variety of summer and winter conditions of the Mediterranean areas of the country. The calculations were performed with an insulated and not-insulated building configurations. Hourly and annual heating and cooling demands were calculated, as well as effective heating and cooling degree days. The results were used to find out simple linear regressions, expressing the energy performance of the building as a function of the roof radiative properties and, as a consequence, measuring the performance of the cool roof product. Limits and potentialities of the method are discussed.

Highly reflective building envelope materials are widely identified as an effective design option to limit the peak surface temperatures of roofs in summer conditions, thus mitigating the urban microclimates and the energy demand for cooling. However, especially surfaces having high solar reflectance are subject to soiling (i.e. deposition of soot and other airborne particles), in addition to ageing, and biological growth. All these processes reduce the reflectance of bright surfaces (and increase the reflectance of surfaces having reflectance lower than roughly 0.20). As a result, an increase in the solar reflectance of a cool roof yields to higher surface temperatures and a reduction in the energy savings expected thanks to high albedo roofing. Furthermore, the durability is also impacted. To quantify this effects, we exposed in the urban environment in Milano and in Roma (Italy) 16 roofing materials. More in detail we selected 14 roofing membranes, including synthetic, factory applied coating on synthetic membranes, field applied coatings on modified bitumen, asphalt shingles, and terracotta tiles. For each product class (e.g. synthetic membranes) we selected a high reflectance product and a mid-low reflectance one. We measured the UV-Vis-NIR spectral reflectance of three samples per product before the exposure – begun in April 2012 – and after 3, 6, and 12 months. Herein we present the results of the first year of natural exposure of roofing membranes, most of which show a remarkable loss in the solar reflectance (sometimes exceeding 15% of the initial value) already after the first three months of natural exposure, depending on their initial value. With the measured curves of solar reflectance over time as input data, we performed finite differences numerical modelling (by means of the software tool WUFI 5.2) of heat and moisture transport through typical roof assemblies. We analyzed the variation in the surface temperature and heat flux due to the change in solar reflectance, and we obtained relevant differences. For instance, in case of a highly reflective flat roof (with initial solar reflectance equal to 0.85, reduced to 0.70 after six months) over 10 cm of extruded polystyrene on a reinforced concrete slab (U-value of the roof assembly equal to 0.277 W m-2 K-1) we computed a significant increase in peak surface temperatures (up to 7°C, from 34.2°C to 41.9°C, assessed in the context of Milano, Italy). Knowledge about the soiling trends for different building envelope materials allows to better estimate the cooling energy demand of buildings, plan cleaning and maintenance operations (whether viable and sustainable), and to assess the benefit of anti-soiling treatments.

"The urban heat island affects our cities and results in. warmer climates in urban areas, as compared to. surrounding rural areas. One solution involves the. use of materials with high solar reflectance and far-infrared thermal emissivity, or “Cool Materials”. Usually cool. materials are used to decrease heat flow entering in a building. But, being their surface temperatures much lower than those of typical building materials, if. used on an urban scale, they lead to a lower heat exchange. between air and surfaces, helping to decrease the air. temperature of the urban environment. The paper reports. the results of a study carried out on a densely populated area of Rome. The study is divided into four parts. a. measure of the urban heat island, comparing temperatures in urban and rural sites; b. analysis of cooling demand of a typical apartment, in rural and urban area; c. thermal. properties of cool asphalts; d. analysis of the urban heat. island, comparing outdoor air temperatures of an area. before and after the adoption of cool materials. The. results demonstrate the significant influence of cool. materials on the reduction of heat island effect. "

Cooling down buildings and cities is becoming a priority as a consequence of the global increase of air temperatures. This effect determines the increase of the energy consumption for cooling, as well as the spread of the urban heat island. Cool materials are characterised by high solar reflectance and high solar emissivity. These two properties allow the material staying cool under the solar radiation. Cool materials deserved attention during the few past years and they started being used mainly to protect the building roofs. This paper presents the first results of the potential benefit of cool materials applied on solar protection devices in residential buildings. External shutters are often used, especially in the Mediterranean countries, for security reasons and for solar protection during the hot season. These components are generally characterised by high solar absorbance, due to the typical used colours: brown, deep green, grey. An experimental campaign was carried out to measure the reflectance of conventional coloured materials versus cool coloured ones. A double beam spectrophotometer was used for the testing activity. The results were used as input for typical Italian dwellings, changing some parameters according to: Climatic conditions, insulation level, the presence of a cooling system, orientation, the position of the dwelling respect to the whole building. The cooling energy demand was calculated through a dynamic simulation tool. A first assessment on the impact of the technology in the Italian residential buildings is hence carried out.

I cambiamenti climatici hanno nel riscaldamento globale una delle manifestazioni più evidenti. L‘aumento delle temperature è un fenomeno generalizzato, cui si associano una serie di rischi ambientali ed energetici. L‘isola di calore urbana è un tipico effetto, in cui fenomeni globali si sommano a specificità locali che portano ad innalzamenti di temperatura significativi in aree densamente urbanizzate. Altra tendenza è l‘aumento dei consumi per la climatizzazione estiva, soprattutto nelle abitazioni, fino a poco tempo fa sprovviste di sistemi di raffrescamento meccanico. I cool materials rappresentano una possibilità per mitigare entrambi i fenomeni, grazie alla possibilità di ridurre il surriscaldamento dei materiali da costruzione per effetto dell‘elevato assorbimento della radiazione solare. I cool materials, caratterizzati da elevate riflettenza solare ed emissività termica, hanno numerose possibilità applicative e sono oggetto di numerosi studi per ottimizzarne le proprietà termo-fisiche e verificarne gli effetti a scala urbana e di edificio. Questo articolo offre una panoramica sulle attività in essere a livello nazionale ed europeo. La prima parte del lavoro presenta le definizioni e le principali tecnologie di cool materials, evidenziandone potenzialità e li-miti. Nella seconda parte sono presentati studi significativi di applicazione a scala di edificio: analisi numeriche con potenziali-tà di risparmio energetico nel settore residenziale e terziario, nonché risultati di attività sperimentali con applicazioni di cool roofs in edifici reali. È infine presentata un‘analisi iniziale di applicazioni di cool materials per asfalti e pavimentazioni in aree urbane, con potenziali riduzioni delle temperature esterne e miglioramento delle condizioni di comfort. Sono infine presentate le principali azioni di disseminazione e sviluppo in essere al livello nazionale ed internazionale.

The urban heat island is a problem that affects our cities and results in a warmer climate in the urban and residential areas compared to the surrounding rural areas. One solution to this problem involves the use of materials with high solar reflectance and high thermal emissivity, the so-called “Cool Materials”. Their surface temperatures are much lower than those of typical building materials. Usually Cool Materials are used to decrease heat flow entering in a building, but if used on an urban scale, their lower surface temperature lead to a lower heat exchange between air and surfaces, helping to decrease the air temperature of the urban environment. The paper reports the results of a study carried out on a densely populated area in Rome of about 500.000 m2. The study was divided into three parts. The first part involves the comparison and the analysis of data collected by weather stations of airports and public agencies located both in urban areas and in peripheral areas in order to monitor the magnitude of the heat island effect. The second part includes measurements of the thermal properties of some Cool asphalts. The third part is focused on numerical analysis of the phenomenon through the creation of a model included in a S.V.A.T. software that allows to compare the outdoor air temperature of an area before and after a hypothetical use of Cool Materials on external surfaces of buildings and street pavements. The results of this study demonstrated the significant influence of cool materials on the reduction of the heat island phenomenon.

"The paper presents the results of a monitoring campaign, performed in the course of the last summer, on a building retrofitted with a “cool roof” material.. The building is a one-storey construction, located on a plot belonging to Roma Tre University, with a total floor area of 275 m2, built in the ‘50s and partially restored in the ‘90s. The building hosts a Cultural and Recreational Center for Senior Citizens, managed by the City of Rome. Users have frequently complained with the management about the uncomfortable thermal conditions during hot periods, despite the presence of air conditioning units.. In fact, a visit to the roof showed that it was flat, not insulated, and that it was covered with a very dark weatherproofing (tar) layer, totally unshaded, which would heat up considerably when struck by strong solar radiation. As a consequence, the internal surface temperature of the ceiling was very high, leading to high Mean Radiant Temperatures, inadequately compensated by the air conditioning, which would cause the uncomfortable conditions.. A research group of Roma Tre University, in cooperation with ENEA, the Italian Agency for Energy and Environment, decided to experiment the use of “cool roof” strategies to improve the situation.. ENEA had already studied and tested several materials, to be used as coatings for roofs and walls. Such materials need to present very high reflectances in the visible-near infrared spectrum (solar radiation), while having high emissivities in the far-infrared range. An Italian company manufactures materials of this kind, which come in rolls and can be easily glued to existing flat surfaces.. First of all, the building has been provided with eleven temperature sensors, five of which to measure outdoor and indoor air temperatures, and the remaining ones to measure surface temperatures, both external (roof) and internal (ceiling). In addition to that, a pyranometer has been installed to measure solar radiation.. All sensors were linked to a data acquisition system, which collected and stored all data. Measures were taken before and after installing the cool roof material. The data acquisition period ran from June 17th to august 31st. The new material was installed on July 19th., covering approximately 120 m2 of roof.. Particularly interesting appear the data collected from July 2nd to 6th and from August 9th to 29th. In fact, during those periods we were able to have the Center closed, without users and with the air conditioning units shut off. That allowed us to analyse surface and indoor air temperatures with and without the cool roof material, thus enabling us to compare the two situations.. We were also lucky because the two periods were very similar in terms of weather and outdoor temperatures.. Finally, the building was simulated using TRNSYS in both situations, first without air conditioning, to check the correspondence between measures and simulation, then assuming continuous air conditioning operation. The first exercise showed the degree of thermal comfort improvement, the last exercise provided an valuation of the energy savings, associated with the adoption of cool roof strategies.. The paper presents the main results of the study, which show a significant improvement in both aspects.. "

Le tecniche di cool roof assumono sempre maggiore importanza nei nostri edifici e nelle nostre città, a causa degli incombenti fenomeni di riscaldamento globale, che hanno forti ricadute sui consumi energetici estivi degli edifici e sulla diffusione del fenomeno dell’isola di calore urbana. Il progetto PROMOTION OF COOL ROOFS IN THE EU è finanziato nell’ambito del Programma SAVE – IEE, con l’obiettivo di favorire la penetrazione della tecnologia nel mercato europeo. Il progetto è improntato su diversi assi, uno dei quali ha a che fare con gli aspetti tecnici dei cool roof. ENEA è responsabile di questo working package ed ha posto in essere della attività a supporto del progetto. È stato implementato il primo database sui materiali per applicazioni di cool roof e una serie di materiali, prodotti in Italia, sono stati testati ed inseriti nel database, scaricabile gratuitamente dal sito web. È stato implementato un caso studio in un edificio pubblico a Trapani, l’analisi dell’applicazione dimostra i benefici derivanti dall’utilizzo della tecnologia in climi mediterranei. È stato infine implementato un calcolatore semplificato per stimare i potenziali risparmi derivanti dall’utilizzo della tecnologia. ENEA ha condotto una serie di simulazioni dinamiche utilizzate per testare e validare lo strumento di calcolo.

Climatic conditions affect shape, colour, geometry and lay-out of buildings. The vernacular Mediterranean architecture was characterised, among other passive techniques, by light colours to minimise solar gains through the opaque components of the building envelope. Actual building design and construction often forget such old bioclimatic approaches, delegating the comfort conditions to artificial systems. The energy consumption increase in the residential sector witnesses this problem, due to the high penetration of air conditioning systems. Ancient concepts, merged with innovative technologies, are hence necessary today. Reflective coatings can reduce the cooling loads with an effective solar control on the building envelope. Photometric analyses were carried out the measure the optical properties of a sustainable light coloured cool paint. Dynamic energy simulations were run for different Mediterranean localities (Rome, Palermo, Seville, Athens, Tripoli), buildings geometry (stand alone and row house), different thermo-physical properties of the opaque envelope (solar reflectance, U-value, thermal capacity) and of the whole building (natural ventilation rates and shading of glazing systems). The influence of reflective materials was assessed respect to the cooling and overall energy demand. The same simulations were repeated considering not cooled dwellings and the related thermal comfort conditions.

The optical properties of the external opaque surfaces (roofs and walls) affect the thermal behaviour of buildings and their energy requirements. The paper explores this complex field with the objective of selecting the optical properties of roofs and walls, granting the best performance, i.e., the minimum energy consumption, given the climate conditions and the other building’s features. The research is based on a vast parametric study, conducted by simulating a typical office building, by means of the TRNSYS code, varying and combining a number of parameters. The study has generated several hundred sets of results, allowing comparisons that, in turns, provide guidelines for selecting the best type of skin properties to adopt in given conditions.

Construction materials for building and urban applications are generally characterised by a diffusing behaviour in response to the incident radiation. With this assumption, reflectance and absorptance values are constant and independent on the incidence angle. This assumption is not valid for regular materials, like glass or polished surfaces, where an angular dependence of radiative properties is observed. However, many opaque construction materials often show a mixed behaviour, which includes reflectance regular and diffusing (or scattering) components. Moreover, the apparent roughness of the materials surface changes according to the angle of incidence of the solar radiation: in particular the higher the latter, the smaller the former. This issue is relevant for cool materials application, where polished and smooth solutions are adopted to increase global reflectance. Directional reflectance properties are to be measured in order to accurately assess the response of the materials surfaces. Gonio-photometry ensures reliable directional measurements on opaque and construction materials and the results can be used for a more accurate building and urban integration of the construction materials: Glare and visual discomfort risk for materials with significant regular components; angular dependent reflectance and the impact on the solar gains and energy balance of the building envelope. Eight typical construction material for roofing and façade systems are measured with a gonio-photometer and a spectrophotometer. The comparison between reflectance values in the visible band obtained with both devices shows a good agreement in four cases with differences ranging between 0.02 and higher discrepancies for the other four samples, with a maximum difference of 0.09. The results provide information about the directional response of such materials and set the frame for new experimental and calculation analyses aimed at a more accurate urban and building integration.