opaque construction materials solar loads calculation dependence on directional reflectance

Abstract Generally the solar reflectance associated to construction material surfaces is considered perfectly diffuse, namely they reflect in every direction the incident irradiance. Therefore reflectance and absorptance are assumed to be constant and independent on the incidence angles. This assumption, generally used in the most of energy analysis simulation tools, has to be considered not valid for materials characterized by a regular reflection, like glass or polished surfaces, where an angular dependence of their optical–radiative properties is observed. However, many opaque construction materials often show a mixed behavior, which includes regular and diffuse (or scattering) reflectance components. Moreover, the apparent roughness of the materials surface changes according to the angle of incidence of the solar irradiance. This issue is relevant for some cool materials, which are polished or treated with other methods to offer a very smooth surface, to increase the solar reflectance. In this work the dependence of opaque materials on the directional properties of their surfaces are investigated to assess the impact on solar loads and energy performances of the building envelope. The reflectance shape and the hemispherical values of two materials used for roofing are measured by means of a goniophotometer to characterize the directional reflectance. A numerical analysis was carried out to compute the differences in solar loads during cold and hot seasons between a reflectance angular dependent model and a constant reflectance model. Sensible discrepancies between the two models put in evidence that solar reflectance angular dependence should be included in the calculation tools to achieve more accurate results

Global energy performance of residential buildings: the role of the urban climate

Abstract The energy performance of buildings are strongly dependent on climatic conditions. Climatic data are acquired by measuring stations, generally located outside of the city, hence their reliability in reproducing the thermal conditions inside the urban environment should be carefully addressed. This paper deals with the analysis of the urban climate in Rome, city characterized by a composite urban texture and a high variability of the residential building stock. Air temperature and relative humidity were monitored in different neighborhoods of the city and in a microclimatic station placed in a countryside area for one year in 2015. The monitoring allowed to quantify relevant microclimatic indicators and to use the data as input to predict the impact on the energy performance of a reference building. It was found that UHI is uniform in winter, while it is zone dependent in summer. UHI hourly intensities reached 10.5 and 7.8°C in winter and summer, seasonal UHI reched 1.5°C in city centre. Urban cooling and heating degree days showed relevant variations up to 26% respect to the countryside area. In terms of predicted energy performance, UHI causes a winter reduction up to 36% and a summer increase up to 42%

Assessment of the Impact of a Centralized Heating System Equipped with Programmable Thermostatic Valves on Building Energy Demand

Abstract The aim of the work presented in this paper concerns the assessment of actual energy savings achieved adopting a common tool of building thermal automation systems such as thermostatic valves. The idea comes from the study of the European Standard CEN EN15232 "Energy performance of buildings - Impact of Automation, Controls and Building Management" which highlights how the inclusion in buildings of automation systems leads to a reduction of energy consumption for the whole building. Starting from here, the actual advantages for the single user in adopting programmable thermostatic valves was evaluated taking into account the possible differences in heating energy demands due to an on/off timetable customization. The case study is a reference building sited in three different locations in Italy with two different values of envelope insulation. By means of Trnsys17 tool the reference building was divided into six thermal zones each one modelling an apartment. The possibility to customize the on/off timetable, through the use of programmable thermostatic valves, may introduce thermal dispersions. As a matter of facts when a user switch off his heating terminals his apartment tends to be a heat sink for the adjacent ones. The purpose of this study is to evaluate if the switching inhomogeneity due to the customization may constitute sensible energy penalties to other users. The results of this study may provide a contribution to the definition of the correct management policies of the terminals customization in order to optimize the use of the building automation systems

On the Solar Reflectance Angular Dependence of Opaque Construction Materials and Impact on the Energy Balance of Building Components

Abstract The solar reflectance of the surfaces is a property that varies according to spectral and angular distribution of the incident solar radiation which in turn depends on orientation and latitude. In this paper, an optical characterization was conducted on some typical opaque building materials, generally used as roof covers: shingles, membranes, bricks and tiles. The measurements were carried out through an experimental factory equipped with a large integrating sphere which allows to measure the spectral reflectance at different incidence angles of the light beam on the sample. Thus it was possible to create a function that linked reflectance values with the incidence angle. The results obtained were included within a dynamic software in order to optimize the calculation of solar gains in the energy balance of a building

Urban temperature analysis and impact on the building cooling energy performances: an Italian case study

Climate changes and urban sprawl are dramatically increasing the heat island effect in urban environments, whatever the size and the latitude are, affecting these latter parameters the effect intensity. The urban heats island is a phenomenon observed since the last decades of the XIX century but demonstrated at large scale only one century later, characterised by the increase of air temperature in densely built urban environments respect to the countryside surround cities. Many studies are available, showing urban heat island intensities up to 12°C. This thermal stress causes social, health and environmental hazards, with major consequences on weaker social classes, as elderly and low income people, it is not by chance that survey demonstrated the increase of deaths in such categories during intense and extended heat waves. This study presents the firs results on the observation of air temperature measures in different spots of Rome, city characterised by a typical Mediterranean climate and by a complex urban texture, in which densely built areas are kept separated by relatively green or not-built zones. Six spots are monitored since June 2014 and include: historical city centre, semi-central zones with different construction typologies, surrounding areas again with various urban and building designs. The paper is focused on the analysis of summer temperature profiles, increase respect to the temperature outside the cities and the impact on the cooling performance of buildings. Temperature datasets and a reference building model were inputted into the well-known and calibrated dynamic tool TRNSYS. Cooling net energy demand of the reference building was calculated, as well as the operative temperature evolution in the not cooled building configuration. The results of calculation allow to compare the energy and thermal performances in the urban environment respect to the reference conditions, usually adopted by building codes. Advice and recommendation of suitable technologies to mitigate such conditions are finally given

OS COMENTÁRIOS DE NAPOLEÃO BONAPARTE A O PRÍNCIPE, DE MAQUIAVEL, CONTIDOS EM NOTAS DE RODAPÉ

Maquiavel escreveu sua obra, O príncipe, no ano de 1513, causando polêmicas que se estendem até os dias atuais, uma vez que é visto como uma espécie de manual para a ação política. Tal livro é de extrema importância, sobretudo no universo político, uma vez que significou um marco da racionalidade política que inaugurou a modernidade. No entanto, fato interessante e pouco analisado são as notas de rodapé escritas por figura tão importante na história mundial como Napoleão Bonaparte. O fato é que não se trata de simples notas e sim de comentários construídos a partir das experiências vividas por Napoleão

A formação do professor e o ensino de matemática

básica em matemática apontam para a necessidade da melhoria da qualidade da educação no Brasil. Com o objetivo de contribuir com o debate sobre a qualidade da educação, este artigo tem como tema central a formação do professor e a proposição de novos cenários para o ensino de matemática. Analisamos os fundamentos epistemológicos que sustentam esta formação, as diferentes concepções propostas para a aprendizagem e as transformações ocorridas no campo da matemática. Para esta análise, consideramos alguns documentos oficiais e o contexto resultante das transformações do ensino da matemática e suas implicações na formação docente. Finalmente, sistematizamos os resultados encontrados em investigações que sugerem novas possibilidades para o ensino da matemática

Desempenho escolar e vulnerabilidade social

Este artigo discute a dinâmica do desenvolvimento e outros conceitos construídos pelo Enfoque Histórico-Cultural como categorias que permitem compreender de forma mais adequada o desempenho escolar de sujeitos em situação de vulnerabilidade social. Demonstra a contribuição da Psicologia para construir, a partir de uma perspectiva interdisciplinar e do pensamento complexo uma explicação mais abrangente do desenvolvimento humano e das relações entre aprendizado e desenvolvimento humano. São  apresentados fragmentos de ações educativas realizadas com dois sujeitos em situação de risco social.Palavras-chave: Educação. Vulnerabilidade social. Desenvolvimento humano

Objetos de aprendizagem: uma análise da aprendizagem matemática e suas concepções tecnológicas

A matemática está presente no cotidiano da sociedade e de cada sujeito e suas implicações sociais, políticas e econômicas justificam refletir sobre suas teorias e a forma de ensinar seus conteúdos. Como parte das ciências humanas ou sociais é caracterizada como uma práxis que envolve um amplo domínio de recursos. Porém, o que vemos hoje nas escolas, em sua maioria, é uma descontextualização do conteúdo ensinado em matemática com a realidade do aluno e uma dinâmica de aula pautada pela teoria e exercícios de fixação. Uma educação matemática crítica pressupõe que os alunos reconheçam os problemas discutidos em sala de aula, como uma realidade vivida fora do ambiente escolar, e que estes conteúdos sejam dotados de significados. Assim, a utilização dos objetos de aprendizagem nas aulas de matemática pode corroborar com professores e alunos, principalmente se apoiado nos ambientes de aprendizagem apresentados por Skovsmose e nas concepções tecnológicas envolvidas na organização de contextos de ensino. Neste sentido, esta comunicação científica, que é um recorte de uma dissertação de mestrado, tem como objetivo classificar os objetos de aprendizagem relacionados com o ensino de matemática presentes no repositório Proativa segundo os ambientes de aprendizagem propostos por Skovsmose e suas concepções, considerando a utilização da tecnologia. O texto resulta de uma sistematização de dados encontrados na literatura, configurando-se como revisão de literatura