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Background Phase change materials (PCMs) have been proposed as a means to increase the thermal inertia of glazing systems. These materials have optical features that need to be investigated and characterised in order to better understand the potential of these systems and to provide reliable data for numerical simulations. Methods The spectral and angular behaviour of different PCM glazing samples, characterised by different thicknesses of PCMs, were investigated by means of commercial spectrophotometer and by means of a dedicated optical test bed that includes a large integrating sphere with a diameter of 0.75 m. Such equipment was necessary because of the highly diffusive behaviour of the PCM layer when in the solid state of aggregation. Results The paper provides a data set of luminous and solar properties of glazing units with PCMs in gaps; the data set uses results from an advanced optical facility that overcomes the intrinsic limitations of commercial spectrophotometers in measuring the optical properties of the advanced transparent materials. In detail, transmittance, reflectance and absorptance spectra of double glazing units characterised by different PCM layer thicknesses in the gap, measured at different incident beam angles, are reported. Integrated values calculated according to relevant international standards are thus provided. Optical features of PCM glazing systems are also highlighted and issues related to the integration of these systems in buildings are discussed. © 2014. This is the authors’ accepted and refereed manuscript to the article. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

Energy saving in the building sector is one of the key issues to achieve environmental targets at national and European Union (EU) levels. Although 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 space cooling. 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 a high solar reflectance, cool roofs tend to decrease the cooling demand and increase the thermal comfort. Energy rating and labelling are a quick solution to compare energy-related products. This paper presents the first studies aimed at the definition of an energy-rating scheme for cool roofs, starting from product properties and reaching building performances. Energy simulation results were used to find out simple linear regressions, expressing the energy performance of the building as a function of the roof's radiative properties and measuring the performance of the cool roof product. © 2014 © 2014 Taylor & Francis.

Highly reflective roofs, widely known as cool roofs, can reduce peak surface temperatures and the energy required to cool buildings, mitigate urban microclimates, and offset CO 2 . However, weathering, soiling, and biological growth affect their solar reflectance. In this study, the solar spectral reflectances of 12 roofing membranes were measured before the exposure and after 3, 6, 12, 18, and 24 months of natural ageing in Roma and Milano, Italy. The membranes with an initial solar reflectance greater than 0.80, for example, decreased in reflectance by 0.14 in Roma and 0.22 in Milano after two years. Then, for a typical highly insulated commercial building, the annual cooling load savings were calculated to be reduced by 4.1–7.1 MJ m −2 y −1 per 0.1 loss in reflectance. When the buildings are non-insulated, the savings reduction is 58–71 MJ m −2 y −1 in Milano and 70–84 MJ m −2 y −1 in Roma. Ageing yielded a reduction of the cooling load savings that could be achieved with a new white membrane of 14–23% in Roma and of 20–34% in Milano. Moreover, in Milano, an aged, white, highly insulated roof, which has a solar reflectance of 0.56, may reach a surface temperature 16 °C higher than a new roof, which has a solar reflectance of 0.80.

Copyright © 2021 The Author(s). The global effects of climate change will increase the frequency and intensity of extreme events such as heatwaves and power outages, which have consequences for buildings and their cooling systems. Buildings and their cooling systems should be designed and operated to be resilient under such events to protect occupants from potentially dangerous indoor thermal conditions. This study performed a critical review on the state-of-the-art of cooling strategies, with special attention to their performance under heatwaves and power outages. We proposed a definition of resilient cooling and described four criteria for resilience—absorptive capacity, adaptive capacity, restorative capacity, and recovery speed —and used them to qualitatively evaluate the resilience of each strategy. The literature review and qualitative analyses show that to attain resilient cooling, the four resilience criteria should be considered in the design phase of a building or during the planning of retrofits. The building and relevant cooling system characteristics should be considered simultaneously to withstand extreme events. A combination of strategies with different resilience capacities, such as a passive envelope strategy coupled with a low-energy space-cooling solution, may be needed to obtain resilient cooling. Finally, a further direction for a quantitative assessment approach has been pointed out. The research is supported by Det Energiteknologisk Udviklings- og Demonstrationsprogram (EUDP) under grant 64018-0578. It was also supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Building Technologies Office of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

The pattern and permeability characteristics that compose three-dimensional (3D) textiles are important as a textile shading component to the architecture, engineering and construction (AEC) industry. Moreover, due to their complex geometry, 3D fabrics require a detailed modeling for correct evaluation of performance. This paper aims to present and investigate the optical properties of six 3D fabrics proposed as an alternative to traditional roller blind shading systems, which could guarantee high daylight availability and visual comfort. The light transmission distribution for the different samples has been characterized by carrying out angular visual transmittance measurements, using integrating sphere optical benches, and virtual modeling using Radiance's genBSDF tool. The Bidirectional Scattering Distribution Function (BSDF) calculated with Radiance shows a good fit with the optical angular measurements, which were used as a benchmark and to calibrate models. The performance of the 3D textiles, in terms of illuminance, daylight availability, and glare, was assessed considering two of the set of 3D textiles as alternative materials for a movable internal roller shade system in an open office. The innovative system was compared with a traditional single layer fabric roller blind under different shading control strategies, 3D fabrics demonstrate the potential of increasing Daylight Autonomy while providing better uniformity and better connection with the outdoors due to a higher openness factor. The shading effect created by the 3D geometry of the textile can increase the openness factor while restricting glare.

A comprehensive review of aerogel glazing systems is provided, focusing on the main properties of interest in building applications. Both granular and monolithic forms are taken into account, even if only the former is available on the market. Reviewed studies regard the material itself and of the assembled glazing systems are analysed. After a short description of the fabrication process, thermal and optical properties are presented, in order to provide a set of useful data on the most important parameters affecting energy and lighting performance of buildings. Not-energy related aspects, as quality of lighting and acoustic properties are also investigated, being relevant for the successful building integration. Numerical analyses and field studies show the potential of the technology to achieve relevant energy savings with respect to conventional glazing systems, especially in cold dominated climates. Long term performance studies confirm the reliability of the technology, with minor functionality issues to be solved. Costs of aerogel are still considerably higher when compared to conventional glazing units, however the fully developed technology may become competitive with the performance required in a zero energy building perspective.

Among water-based mitigation strategies against urban overheating, dry mist systems are especially promising, given their local impact, cost-effectiveness and controllability. Intense cooling capacity has been reported under a variety of climates, however, there is a growing need to define specific design guidelines towards an informed and optimized use of the technology. Parametric analysis on validated models would assist in determining type and degree of correlation between key parameters, as well as magnitude and predictability of the cooling capacity. In this paper, for the first time, a 3D microclimatic model in ENVI-met is used to simulate a misting system installed in Rome, Italy, with high prediction accuracy for the air temperature (R2≃0.87, RMSE≃0.84 °C). The calibrated ENVI-met model is used then to perform parameterizations on the water mist system, focused on the role of three key design variables: i) water flow rate, ii) injection height and iii) local wind speed. Results show that the most significant thermal drops tend to occur close but out of the misted perimeter following the wind direction, with cooling effects further stretched for tens of meters. The cooling capacity increases with the total water flow rate (+0.2 °C per 10 l/h increment) and in presence of calm air (+35–40% per 0.8 m/s deceleration). Lower injections intensify the cooling a pedestrian height, which could be especially beneficial under windy conditions. Further research would target climate dependencies to extend the applicability of the above results and build up cohesive guidelines at the hands of urban planners and practitioners.

Climatic conditions strongly affect the energy performance of buildings, and due to the synergy between global climate change and the Urban Heat Island (UHI) effect, the climatic conditions inside and outside the city are highly different. However, weather data collected at airports are commonly used for building energy simulations and these data do not take into account real temperature distribution in cities. Many studies in the literature address the topic but mostly considering only a couple of urban and non-urban stations. In this paper, the urban climate in Rome, Italy, is analysed after monitoring of the air temperature and relative humidity in four selected neighbourhoods and one reference station from October 2014 until September 2017. Rome is characterised by a composite urban pattern and high variability of building types, of which the four selected areas are representative. The heating degree days decrease up to 18% and cooling degree days increase up to 157% in the urban area with respect to the rural reference and the area most affected by the UHI is the city centre. The UHI is more intense in summer than in winter (average increase between 0.7 °C and 1 °C); while the diurnal and nocturnal UHI depends on the season and the neighbourhood. Then, the energy performance of a representative apartment block and a typical office building was computed using the measured data. Regarding the predicted energy performance, comparing the four urban sites and the reference site, the UHI causes a reduction of heating consumption up to 21% in residential building and 18% in the office building. An increase of cooling consumption up to 74% is instead computed for the residential building and up to 53% for the office building. © 2018 Elsevier Ltd

Wall finishes with high solar reflectance and thermal emittance, commonly known as cool walls, can reduce the exterior surface temperatures of façades, and consequently the building cooling energy needs and power demand, and lower the sensitivity to degradation. Aging, though, may affect their performance. To investigate this risk, we exposed for four years in Milan, Italy, two series of façade finish coats, white and beige, facing north and south, in vertical and vertical-sheltered position, and we measured their solar spectral reflectance and thermal emittance before and after aging. The solar reflectance of the white finish coats drops from 0.75 to 0.55 in four years, and from 0.46 to 0.38 for the beige coats, while the thermal emittance is unchanged. Then, for a typical residential building with white walls, we computed that the cooling energy needs increase with walls aging by 5% and 11%, respectively, with or without exterior wall insulation. The exterior surface temperature is increased even by 6 °C, and the number of sudden surface temperature variations in one hour is boosted. Finally, the moisture content in the external layers is reduced, showing the impact on the heat and mass balance because of the uncertainty in solar absorption due to aging. © 2017 Elsevier B.V.

An experimental study was conducted to improve the comfort and liveability of urban open spaces during the hottest months of the summer by implementing an overhead water mist cooling system. The campaign was conducted in two different Italian urbanscapes (Ancona and Rome, representative of Cfa and Csa climates) one after the other. Monitoring data and comfort questionnaires were combined to extract useful information by means of statistical tests, regressions and data mining algorithms and, ultimately, to delineate design and operating guidelines to maximize people's satisfaction with the misted environment. The cloud of droplets reduced the temperature and the UTCI by 8.2 °C and 7.9 °C respectively, against a 7% mean humidity premium. The vertical cooling and humidification profiles obeyed a Lorentzian distribution, peaking within approximately 0.5 m of the injection. The severe overheating experienced outside of the cooled areas evanished under the spray, with 67% (Ancona) to 90.6% (Rome) of respondents reporting only slight bending from thermal neutrality. Perception and preferences towards solar radiation, humidity level and wind all improved within the droplets mist. In terms of comfort-oriented, optimized design criteria, the system proved to work best with a dominant and steady light breeze (1–2 m/s), in highly irradiated sites and suspended at 1.2–1.5 m above the average height of users.

Concerning Nearly Zero Energy Buildings, it is important to guarantee energy efficiency, thermal comfort and indoor environmental quality, while keeping construction and operational costs low. In this framework, this paper explores the efficacy of applying different scenarios, for reducing construction costs of new nearly zero energy multi-family houses in a life cycle perspective. Conversely to the standard cost-optimal approach, a real Italian case study building was chosen. Alternative and unconventional combinations of solutions for envelope and technical systems were adopted. Calculations were performed in two Italian cities (Rome and Turin). Three types of analysis were developed thermal comfort, energy performance and financial calculation. Results of the thermal analysis show that the installation of active cooling to prevent summer overheating can be avoided by applying low-cost passive strategies. All the proposed low-cost scenarios (4 alternative scenarios in Rome and 5 in Turin) reached the highest grade of energy performance, with a reduction of the non-renewable primary energy consumption up to 46% compared to the base case in Rome and 18% in Turin. From the economic perspective, all the scenarios in the two climate zones allow both reductions in the construction costs, up to 26% in Rome and 15% in Turin, and a Net Present Value after 50 years up to 163 €/m2 in Rome and 158 €/m2 in Turin.

Thermochromic switchable glazing have been gaining increasing popularity among dynamic building envelope solutions aimed at reducing energy demand in tertiary buildings, due to their capability of varying optical properties according to the material temperature. This enables the management of entering solar loads without any need for an active control, hence thermochromic glazing performance relies on effective material design. Nevertheless, to date the development of thermochromic glazing materials has relied on limited building performance evaluations, considering the effect of managing solar radiation on energy use for heating and cooling alone, and without representing in a comprehensive way the variations of the thermochromic optical properties to include hysteresis phenomena. The present paper aims to evaluate the building performance of a ligand exchange thermochromic glazing (LETC), characterised by a wide variation of optical properties in the visible and solar spectra and hysteresis between heating and cooling cycles. To this aim an ad-hoc developed building performance simulation strategy is presented, enabling data integration between dynamic thermal simulation and climate based daylight analysis, including a thermochromic parametrical model describing the hysteretical variation of optical properties as a function of material temperature, derived from experimental measurements. The simulation method is adopted to evaluate the energy uses for heating, cooling and lighting and the visual comfort in an office space integrating the LETC glazing in different climatic contexts. The results show that the LETC glazing is able to optimise multiple building performance aspects simultaneously. Compared to static glazing benchmarks with comparable selectiveness, for the considered locations, the LETC glazing achieves a total energy use reduction from 3% to 10% and daylight availability improvements from 5% to nearly 20%. Increasing the thermochromic hysteresis has shown a positive effect on improving daylight availability (from 5% to 15%) and on reducing probable glare due to direct solar radiation (from 12% to 25%), with negligible effect on total energy use. Finally, the simulation framework presented represents a general method that can be adopted to evaluate the performance of other switchable glazing technologies as well.

Several mature urban climate mitigation technologies have been proposed to date. What mostly hinders their wide implementation is that their efficiency heavily depends on the local microclimatic specificities, since they cannot self-adjust to the environmental changes. This study aims at investigating benefits and impacts of smart logics applied to outdoor cooling, by field testing a web of nebulizers coupled to a bespoke fuzzy controller piloting the pump. The cooling action was tweaked as convenient to maintain comfortable conditions and to avoid energy wastage whenever unneeded. To the best of the authors’ knowledge, this is the first application of fuzzy logic to water spraying systems (or to any other controllable urban climate mitigation technology) targeting comfort and energy optimization. The prototype was field monitored in comparison with the conventional on-off control, in two Italian urban contexts (Cfa and Csa climatic zones) over 15 days in the hottest months of the year. The cooling and humidification action was thoroughly characterized by mapping both the horizontal and vertical profiles and by applying advanced Artificial Intelligence techniques to spot the main environmental drivers. The maximum cooling (measured between the sprayed area and an undisturbed reference) touched 7.5 °C and 6.14 °C in the two locations, respectively. The energy saving achieved under fuzzy control versus the temporized control, was spectacularly high in the wetter and windier location with an average of −51.2% and a maximum of −67.5%. The comfort benefit was also substantial: the temperature never deviated from neutrality by more than ±2 °C, whereas with the on–off, this threshold was surpassed between the 14% and the 20% of the time by even more than 5 °C. The results suggest that smartly controlled nebulization is an energy-efficient and comfort-effective strategy to counteract urban overheating. Furthermore, solar-powered solutions are well suited as proved by the preliminary design estimation we included.

The paper deals with the experimental characterization of double glazing units with granular aerogel in cavity at laboratory and pilot scale. In the laboratory investigation, three granule sizes and three aerogel layer thicknesses (10–35 mm) were considered. Light transmittance is in the 0.41–0.75 range (the highest values for the highest granule size and the minimum thickness). The U-value is 1.5 W/m2 K with 10 mm aerogel, whereas it decreases to 0.5 W/m2 K when considering 35 mm of aerogel, regardless of the granules size. After a systematic characterization, aerogel with large granules, the most common on the market, was chosen for an investigation at pilot scale. A window composed of two 6 mm clear float glasses and 15 mm aerogel in gap was tested in an experimental field with two boxes, in comparison with a conventional window. Aerogel sample allowed a reduction in the peak value of the indoor temperature of about 8–9 °C during sunny days, while similar values were achieved in the two test boxes during the night.

Climate changes and urban sprawl dramatically increase the urban temperatures and the thermal quality in the built environment. Among several proposed mitigation techniques, cool roofs have now reached a broad audience, while the cool materials potentialities for façade applications are still little investigated. A novel masonry paint, produced with the inclusion of cool pigments, is investigated in this paper. A palette of colour is developed with the objective of covering a wide range of architectural integration solutions. Reflectance and emissivity are measured and calculated. The results strongly depend on the base colour used to prepare the sample; solar reflectance increase up to 0.16 is achieved for dark colours. A numerical analysis is carried out to evaluate the impact of the cool paint on the thermal response of a typical Italian residential building. Energy uses are calculated for different insulation levels and climatic conditions. Cooling energy uses are reduced in the 10-20% range; total energy uses are affected by several parameters with 5% maximum savings. Peak operative temperature reductions range from 0.5 to 1.6 °C for the building in free floating conditions, according to climate and insulation level. External surface temperatures are reduced above 6 °C during the peak irradiation hours. © 2015 Elsevier B.V. All rights reserved.

Large transparent surfaces in building façades can be a cause of high energy demand and discomfort conditions in buildings. Since standard static solutions for glazing and shading devices are not sufficient to overcome these drawbacks, a new dynamic shading device based on the integration of phase change materials (PCM) in an alveolar polycarbonate panel was proposed. The concept of the innovative translucent shading is to act as a self-controlling device able to reduce and modulate both light and solar heat gain in the indoor environment and to improve the thermal inertia of the envelope. To provide input data for energy and daylighting computational tools on a building scale, a complete thermal and optical characterisation of the PCMs and of the dynamic shading systems was carried out. Different typologies of PCM (paraffin waxes, salt hydrates and bio-based PCMs) with different melting temperature (in the range of 26–44 °C) and different colour of the polycarbonate panel (blue, green, opal and crystal) were investigated. Specific experimental protocols were implemented to compare the properties of various configurations of the new technology. Results show that the preferable PCMs are the paraffin waxes, due to their stable thermal properties, high latent heat of fusion and narrow melting temperature range. With regard to the thermal resistance of the system, a slightly better performance was measured with the bio-based PCM. According to the optical characterisation, it can be stated that the preferable colours of polycarbonate are green and crystal. The outcomes are promising, but several limits still need to be overcome at the technological and architectural level. © 2017 Elsevier B.V.

Polycarbonate panels could be considered as a suitable and cheap solution for walls, roofs, and sheds in non-residential buildings and, at the same time, granular silica aerogel is one of the most promising nano-materials for energy saving in buildings. In the paper, three types of advanced multiwall PC panels (thickness 16, 25, and 40 mm) with translucent granular aerogel were investigated by experimental (thermal and optical) and numerical characterization. By comparing thermal performance of air and aerogel-filled PC systems, it can be noticed that the impact of the aerogel is remarkable: the reduction in U-value is 46%-68%, depending on the aerogel layer thickness. U-value is 1.4 W/m2K for the 16 mm thickness sample and it is 0.6 W/m2K when the thickness increases up to 40 mm. The systems keep their performance in horizontal position, when they are used as roofs. Light transmittance is 0.61 and 0.42 for 16 mm and 40 mm respectively and the reduction with respect to air-filled panels is acceptable (15%) for 16 mm and significant (40%) for 40 mm thickness. The aerogel has also a remarkable impact on the reflectance spectrum, especially between 400 and 1400 nm. The solar factor is 0.58 for 25 mm thickness, quite similar to the low-e glazing one. Finally, energy simulations for a case study showed that aerogel-filled PC systems outperform conventional double glazing systems both for heating and cooling energy demands. However, when compared to low-e glazings, the benefits of the translucent material (also considering the highest thickness) in the interspace are lower for heating and negligible for cooling energy demands. The aerogel-filled polycarbonate systems could be a valid solution for non-residential buildings, enhancing the thermal performance and the light control of the building envelope, especially when they are used as roofs. © 2018 Elsevier B.V.

The paper deals with the potential of high energy-efficient windows with granular silica aerogel for energy saving in building refurbishment. Different glazing systems were investigated considering two kinds of granular silica aerogel and different glass layers. Thermal transmittance and optical properties of the samples were measured and used in building simulations. The aerogel impact on heat transfer is remarkable, allowing a thermal transmittance of 1.0-1.1 W/(m2.K) with granular aerogel in interspace only 15 mm in thickness. A 63% reduction in U-value was achieved when compared to the corresponding conventional windows, together with a significant reduction (30%) in light transmittance. When assembled with a low-e glass, the U-value reduction was lower (31%), but a moderate reduction in light transmittance (about 10%) was observed for larger granules. Energy simulations for a case study in different climate conditions (hot, moderate, and cold) showed a reduction in energy demand both for heating and cooling for silica aerogel glazing systems, when compared to the conventional ones. The new glazings are a suitable solution for building refurbishment, thanks to low U-values and total solar transmittance, also in warm climate conditions. © 2017 by the authors.

The energy renovation of the existing building stock is a crucial strategy to achieve environmental targets at national and EU levels, as demonstrated by current energy uses and potential energy savings in the construction sector. The retrofit of school buildings in Italy is relevant because of the poor energy performance of the stock, as well as for its high social value. The Tito Maccio Plauto school in Cesena went through a deep energy retrofit process in the framework of the “School of the Future” EU Project. This paper documents all the phases of the process: the initial energy and indoor environment assessment; the design phase supported by detailed calculation analysis; the two years monitoring phase after the conclusion of the renovation works. The energy monitoring demonstrated a factor 4 reduction of space heating, final and primary energy, as well as the electricity neutrality achieved after the retrofit. Also the indoor environmental quality was addressed in this study by means of instrumental monitoring of indoor parameters and subjective analyses, carried out by a dedicated questionnaire. These additional actions demonstrated the positive impact of the implemented measures on thermal comfort and indoor air quality, as well as other co-benefits. © 2016 Elsevier B.V.

Building envelope materials containing titanium dioxide have been proposed to exploit their photoactivated depolluting and self-cleaning potential, but a full appraisal of their durability and long-term performance is still missing. This study reports a two-year campaign of natural exposure in Milano, Italy, of photoactive and non-photoactive fiber-reinforced mortars, analyzing the evolution of lightness, solar reflectance, porosity and photoactivity. After aging, photoactive samples showed limited color variation. The photocatalytic activity of TiO2 containing samples, characterized with dye degradation tests, was minimal after aging. Then, after alternated cycles of UV-Vis irradiation and rinsing, almost 70% of the initial photocatalytic efficiency was recovered. © 2015 Published by Elsevier Ltd.

Plastic transparent components are increasing their share in the glazing market since they provide good performance with a weight significantly lower than glass and at competitive costs. Typical products are coextruded polycarbonate multi-sheets systems, UV-protected to avoid the quick ageing. These components have limitations on the size and need to be bonded each other via male-female joints that could be a weak point for the façade. This study is focused on the thermal and optical characterization of three polycarbonate systems for buildings (with different number of chambers and geometry). Thermal transmittance measurements were carried out using a hot-box apparatus, in order to assess the impact of the connection joints on the effective U-value and to compare it with data declared by manufacturers, usually referred to the centre of the component. The optical characterization was carried out to monitor the same issue for the light and solar properties, by means of a large integrating sphere apparatus. The investigated polycarbonate systems could be a valid solution in place of classic windows in commercial buildings and the study provides a deepened knowledge about the polycarbonate panels' thermal and optical behaviour and a set of useful data for accurate analyses in building integration. © 2013 Elsevier B.V.

The vernacular Mediterranean architecture was characterised by passive solutions able to ensure thermal comfort conditions in the built environment during the hot season. The use of light colours to redirect most of the incident solar radiation was based on these traditional solutions. Cool roofs are a mix of ancient concepts and modern technologies; their application in new and existing buildings can significantly improve the energy efficiency during the cooling season and throughout the year. The paper reports the results of a large application in an office/laboratory building belonging to a school campus in Trapani, on the west coast of Sicily. The experiment was carried out in two phases. The building was continuously monitored during the first phase from late April to late September 2009: indoor and outdoor air temperatures, relative humidity and solar radiation were acquired. The monitoring was carried out before and after the cool eco-friendly white paint application, characterised by high solar reflectance and thermal emittance. The monitored data were used to calibrate the building model input into a dynamic simulation tool, used to evaluate the building performance with a number of variants. The analysis gave interesting results on the potential of this technique for the southern European climatic conditions. © 2011 Elsevier B.V.

The Urban Heat Island (UHI) effect is defined as the increase of the urban air temperature compared to surrounding rural areas. The phenomenon is experienced at all latitudes and, combined with the global warming, has a severe impact at environment, energy and health level. The increasing of solar reflectance of urban materials is a strategy aimed at reducing surface and air temperatures and at mitigating the UHI. Cool materials applied to conventional asphalts are a viable technology for such purposes. The optical and thermal characterisation was carried out in laboratory and outdoor, and showed the enhanced properties and performances of several cool asphalt samples compared to conventional materials. The experimental data were used as input to simulate the thermal environment of a densely populated neighbourhood in Rome, estimating the effect of the roads albedo on the temperature air profile. Simulations performed with the software ENVI-met showed a significant reduction of air temperature closely correlated with the road solar reflectance. The air temperature profiles were used as input to calculate the impact of the albedo change at the building level. Simulations on the peak cooling demand of typical Italian dwellings were carried out by means of the TRNSYS dynamic simulation tool. Peak reductions of almost 19% were calculated for the highest solar reflectance configuration. © 2012 Elsevier Ltd.

Cooling down buildings and cities is becoming a priority as a consequence of global increase of air temperatures. This effect determines the growing of energy consumption for cooling, as well as the spread of urban heat island effect. Cool materials are characterised by high solar reflectance and high infrared emissivity. These two properties allow the material to stay cool under the solar radiation. Cool materials are deserving attention to mitigate surface temperatures in buildings and urban materials. This paper presents the first results of the potential benefits of cool materials applied on solar protection devices. Shutters are used for security and for solar shading in Mediterranean countries. These components are generally characterised by high solar absorbance, due to the colours traditionally used. An experimental campaign was carried out to measure and compare the optical and thermal properties of conventional and cool coloured materials. The results were used as input to assess the impact of these products in Italian dwelling, taking into account several variables: climatic zone, insulation level, and operative conditions. The cooling energy demand and the thermal comfort conditions were calculated with an hourly heat balance building simulation tool.