196,644 research outputs found
On the impact of modified urban albedo on ambient temperature and heat related mortality
No full textUrban heat island and regional climate change raise the ambient temperature in cities and increase the levels of heat related mortality. Higher albedo values lower the ambient temperature and reduce the impact of excess urban heat on health. The present work reviews and analyses fourteen detailed studies investigating the impact of increased urban albedo on the ambient temperature and heat related mortality. It is found that the real magnitude of the afternoon temperature drop caused by the albedo increase is close to 0.09C per 0.1 rise of the albedo, and it is highly determined by the specific climatic, landscape and layout characteristic of cities. A statistically significant association of the temperature drop with the albedo increase, the greenery and street ratio in cities is found. It is observed that the levels of heat related mortality increase significantly as a function of the population size of the cities and the local poverty levels, Increased urban albedo is found to reduce heat related mortality between 0.1 and 4 deaths per day, corresponding to an average decrease of deaths close to 19.8% per degree of temperature drop, or 1.8% per 0.1 increase of the albedo. Mortality drop is found to be in statistically significant association with the initial heat related mortality levels, albedo increase and socioeconomic parameters like the local poverty levels. Accurate parametric functions to predict the magnitude of the temperature drop and heat mortality reduction are developed
On the mitigation potential of higher urban albedo in a temperate oceanic metropolis
No full textThe urban overheating calls for the implementation of mitigation actions. The article aims at demonstrating the advantages and the risks associated with the increase of the city albedo in Melbourne (Australia), through high resolution numerical analyses based on a detailed urban land use. The Weather Research and Forecasting model was used to calculate the spatial and temporal local climate change for three increased albedo scenarios and three different urban densities. In the scenario with highest albedo, the ambient temperature decreases of about 1.6°C in the middle and high density zones and 0.9°C in the low density zones. The sea breeze extends the thermal benefit due to the albedo increase to non-urban areas, despite it is slightly weakened by the diminished land-sea temperature contrast. The pollutant levels are expected to increase, due to a combination of slower winds (drops up to 0.19 ms−1) and decreased planetary boundary layer heights (drops from 175 m up to 291 m). High and low density classes have the highest and lowest risk of stagnation, respectively. Due to the contrasting results in terms of thermal mitigation and pollution risks, the study calls for the identification of comprehensive metrics to asses optimal values of urban albedo
Investigating the effects of the greenery increase on air temperature, ventilation and cooling energy demand in Melbourne with the Weather Research and Forecasting model and Local Climate Zones
Full text linkVegetation has a well-known potential for mitigating urban overheating. This work aims to explore the effects of enhancing urban greenery in Melbourne (Australia) through a configuration of the Weather Research and Forecasting (WRF) model including the Building Effect Parameterization and the Local Climate Zones and presents novelties in: i) covering two-months and ii) focusing on air circulation and buildings cooling energy demand through the ventilation coefficient (VC) and the cooling degree hours (CDHs). A control case and two “what-if” scenarios with a growing green coverage equal to 35 % (control case), 50 % (modest increase) and 60 % (robust increase) have been designed and then simulated for January and February 2019. Outcomes reveal a maximum drop in 2 m temperature of approximately 0.4 °C and 0.8 °C at 14:00 LT for the modest and robust green increase scenario, respectively. The urban-rural energy surplus for cooling buildings is reduced and even counterbalanced. Peak CDHs decrease from 143 °C·h of the control case to 135 °C·h (modest increase) and 126 °C·h (robust increase), while they measure 137 °C·h in the non-urban areas. Average wind speed increases by 0.8 m/s (equal to 22 % with respect to the control case). Furthermore, adding urban greenery has an unfavorable implication on VC (maximum reduction of 500 m2s−1) with a consequent deterioration of the transport and dispersion of pollutants. Middle- and high-density classes are touched more than low-density by the VC reduction. In addition, the benefits of enhancing urban greenery concern physiologically and psychologically the quality of life of the dwellers
Applicazioni di cool materials per l'efficienza energetica negli edifici e la mitigazione dell'isola di calore urbana. Stato dell'arte e prospettive in Italia e in EU
No full textI 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
High Performance Technologies and the future of architectural design
Full text linkHigh Performance Technologies and the future of architectural desig
Analysis of a cool roof system for reducing cooling loads and improving cooling system efficiency
No full textGaining confidence in models of experiments in existing buildings
No full textDescribes a method for gaining confidence in models of experiments in existing buildings
Influência da refletância e da emitância de superfícies externas no desempenho término de edificações
Full text linkDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Civil, Florianópolis, 2014.As edificações são responsáveis por muitos impactos ambientais, grande parte deles relacionados ao consumo de energia. Uma das principais parcelas desse consumo é destinada ao condicionamento de ar e poderia ser minimizada através da melhoria do desempenho térmico das edificações. As propriedades radiantes das superfícies (refletância solar e emitância térmica) do envoltório do edifício são essenciais nesse processo, pois são responsáveis pelo comportamento das superfícies com relação à radiação. Em alguns países, estão disponíveis materiais de construção indicados para favorecer a eficiência energética, como os chamados ?revestimentos frios?, que possuem alta refletância e alta emitância. O objetivo geral deste trabalho é analisar a influência da refletância solar e da emitância térmica de superfícies externas no desempenho térmico de edificações nos diferentes climas brasileiros. Foram realizados experimentos e simulações computacionais. Na análise experimental foram medidas e analisadas amostras de tintas com diferentes refletâncias e emitâncias ao longo de um ano. Essa análise permitiu a verificação da confiabilidade da simulação computacional e também indicou o efeito da degradação natural nas propriedades superficiais das amostras. Os resultados mostraram que a exposição às intempéries teve maior impacto sobre a refletância solar do que sobre a emitância térmica das superfícies. Nas amostras de cor branca, a exposição provocou reduções de até 15% em suas refletâncias. Verificou-se, ainda, que os impactos da exposição foram provocados principalmente pela deposição de sujeira e que com limpeza periódica é possível manter a refletância solar próxima ao valor inicial. Nas simulações computacionais, um modelo de edificação residencial, com variações nas propriedades superficiais do envoltório, foi analisado para os diferentes tipos de clima brasileiros. Tais simulações demonstraram o impacto do uso de revestimentos com diferentes valores de refletância e de emitância no desempenho termo-energético do modelo, para cidades nas diferentes zonas bioclimáticas do Brasil. Confirmou-se a indicação de revestimentos com elevada refletância solarviiipara quase todo o território brasileiro. Entretanto, o mesmo não ocorreu com relação à emitância térmica. Para cidades de clima temperado (especialmente nas zonas bioclimáticas de 1 a 3) as simulações indicaram a adoção de valores menores de emitância térmica na superfície externa do envoltório, para melhorar o desempenho térmico no balanço anual. Dessa forma, pode-se dizer que os materiais frios não devem ser indicados indistintamente para todas as cidades, mesmo no Brasil.Abstract : Buildings are responsible for many environmental impacts, mostly related to energy consumption. An important part of this consumption is due to air conditioning and could be reduced by improving the thermal performance of buildings. The radiation properties of surfaces (solar reflectance and thermal emittance) of the building envelope are essential in this process, as they are responsible for the behavior of surfaces due to radiation. In some countries, there are available construction materials indicated to increase energy efficiency, as the cool materials, which have high reflectance and high emittance. The objective of this work is to analyze the influence of solar reflectance and thermal emittance of external surfaces on the thermal performance of buildings under different Brazilians climates. Experiments and computer simulations were performed. In the experimental analysis samples of paints with different reflectances and emittances were measured and analyzed during one year. This analysis allowed the verification of the computer simulation reliability and also indicated the effect of natural degradation in radiation properties of the samples. The results showed that exposure to weather had a greater impact on the solar reflectance than on the thermal emittance of surfaces. For white color samples, exposure caused reductions of up to 15% in their reflectance. It was also found that the impacts of exposure were mainly caused by the deposition of dirt; and it was possible to keep solar reflectance close to the initial value with regular cleaning. A model of residential building, with variations in radiation properties of the envelope, was analyzed for different Brazilian climates by means of computer simulation. These simulations demonstrate the impact of the use of coating with different reflectances and emittances in the thermal performance of the model for cities in different bioclimatic zones of Brazil. The results confirmed that the use of coatings with high solar reflectance is recommended for almost all Brazilian territory. However, the same cannot be said about thermal emittance. In temperate cities (especially in bioclimatic zones 1 to 3) it would be appropriate to adopt lower values of thermal emittance on the outer surface of envelope, to improve the thermal performance on the annual balance. Therefore, it canxbe said that cool materials should not be used indiscriminately in all cities, even in Brazil
Technologies and socio-economic strategies to nZEB in the building stock of the Mediterranean Area
No full textThe greatest potential for energy savings in the EU is in its existing buildings. The concept of Zero Energy Building (ZEB), which represents the main future target for the design of new buildings, is now gaining an increasing attention in relation to the renovation of existing buildings, as well. This is exceptionally challenging considering the general context of economic crisis in the EU and, particularly, in the Mediterranean areas, currently experiencing high level of unemployment, poverty and social exclusion.
This chapter presents and discusses some progress in low and zero-energy research and practice. It contains a brief review of the current policy background and case studies, and a set of demonstration projects containing evaluation and demonstration procedures that consider the technical, economic and social feasibility of nearly zero energy buildings in the Athens metropolitan area
Microclimatic Improvement.
No full textMicroclimatic improvement can be defined as the mitigation of micro- climatic conditions on a local scale, and it produces, together with the quality of the building envelope, comfortable interior spaces, sheltered from the inclemen- cies of climate. From this point of view, the mild Mediterranean climate offers very interesting features to explore. Its warm winters and mild, dry summers allow for designing open spaces as buffer zones, close to the building envelope. This favorable climatic condition is not exclusive to southern Europe and North Africa, but extends to parts of California, Chile, South Africa, and Australia. The open areas designed to mitigate climate also blur the boundaries between inside and outside. Since they fall inside the comfort zone most of the year, they can be considered an extension of the living rooms, suggesting a rich interplay between interior and exterior spaces. This chapter introduces some basic notions about microclimate, and illustrates some relevant examples to investigate the fundamen- tal design topics related to microclimatic improvement. From Moorish architecture until the present, the idea of mitigating climate through the design of open spaces inside or around the building has produced a vast array of configurations that fea- ture both proven efficiency and an imposing spatial quality. All these architectural spaces can be considered efforts to tame the energy fluxes flowing through the site and make them part of a spatial concept, improving and enriching the quality of space. The result is an exploration of the complex relationship between inside and outside, a study on the continuity of artifice from the enclosed volume to the outer space, and a different point of view of one of the fundamental questions of archi- tecture: the act of enclosing
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