Effect of urban albedo surfaces on thermal comfort

Thermal comfort was and remains a major concern of the designers, makers, planners, climatologists and others, seeking at all costs to ensure the well-being, good health and comfort of citizens in both outdoor and indoor areas. They have addressed this issue in order to identify the main causes that generate the warming of urban areas and therefore contribute to the degradation of the exterior and interior thermal comfort of the inhabitants. It turns out that the reflectivity of materials known as the albedo, plays a leading role in this degradation. A numerical study was carried out to assess the thermal comfort of citizens by applying reflective materials for roofs, facades and floor. The results show that the reflective light paints help in moderating the microclimate, contrariwise, they participate in the degradation of thermal comfort.Keywords: Reflectivity; Materials; Envi-met; Rayman; Degradatio

Effect of kinetic façades on energy efficiency in office buildings - hot dry climates

In hot dry climates excess solar gain may result in high cooling energy consumption and indoor discomfort; sun control and shading devices is an important aspect of many energy-efficient building design strategies. Advanced CAD systems that integrate computational tools, such as parametric design systems, make possible and explore ways to formulate a responsive building envelope that could interact with sun position. The parametric design provides innovative building envelopes, which are more adaptive and interactive by actively responding to prevailing weather conditions, for enhancing energy performance and indoor thermal comfort levels. This study attempts to examine and evaluate the effect and performance of smart façades in the context of the indoor thermal comfort and energy efficiency. These parameters are achieved by controlling the levels of solar radiation and by calculating shading element sizes for sun control in response to environmental changes. In order to ensure the systems autonomy the semi-transparent PV modules has been used as panel's material. The method is applied to the case study of a reference office building with a fixed glazed façade windows-to-wall ratio in hot arid climate zone of Algeria, in particular the city of Biskra (latitude 34.6N). The results obtained from modeling simulation, using GECO- grasshopper (parametric plugin for Rhinoceros), shown That kinetic facades equipped with PV modules have greatly influenced in a positive way the indoor air temperature, thermal and visual comfort levels and also, work towards a better environment for the inhabitants instead of simply being the part that separates the interior from the exterior

The impact of the urban canyon geometry in the nocturnal heat island intensity: analysis by a simplified model adapted to a GIS

A geometria urbana é um dos fatores de maior influência na intensidade da ilha de calor urbana. Seu estudo requer a caracterização de cânions urbanos, geralmente medidos pela relação entre a altura dos edifícios e a largura da rua (H/W), conceito aplicado no modelo numérico de Oke em 1981. O objetivo deste artigo é verificar o impacto da geometria do cânion urbano na intensidade de ilhas de calor noturna. Para isso, foram realizados levantamento de dados climáticos e de geometria urbana em duas cidades brasileiras. Os valores de intensidade de ilha de calor foram confrontados com os simulados pelo modelo original de Oke (1981), o qual foi calibrado e adaptado à plataforma SIG, de forma a possibilitar a incorporação de outro parâmetro de geometria, além da relação H/W: o comprimento de rugosidade. Esse processo gerou uma nova ferramenta de cálculo, que é denominda THIS (Tool for Heat Island Simulation). Aplicou-se o novo modelo para simular alguns cenários urbanos hipotéticos, que representam vários tipos de cânions urbanos. Os resultados demonstraram que cânions urbanos de maior rugosidade amenizam as intensidades de ilha de calor noturna em relação a um cânion de mesmo valor de relação H/W e menor rugosidade.Urban geometry is one of the main factors influencing the development of urban heat islands. The study of urban geometry requires a characterization of urban canyons, which can be usually measured by the H/W ratio (a relationship between the height and the width of a street), a concept applied in a numerical model by Oke in 1981. The aim of this paper is to verify the impact of the canyon geometry on the intensity of the nocturnal urban heat islands. For this purpose, measurements of climate data and urban geometry were conducted in two Brazilian cities. The values of heat island intensity were cross-examined to those generated with the application of the original Oke's model. Therefore, this latter was calibrated and adapted to run in a GIS platform, allowing the incorporation of a geometric parameter other than the H/W ratio - the roughness length. Then, this process produced a new calculation tool, which is called THIS (Tool for Heat Island Simulation). The new model was applied to simulate some hypothetical urban scenarios representing several urban canyons types. The results showed that the urban canyons with the largest roughness reduce the nocturnal heat island intensities in relation to an urban canyon of the same H/W value, but presenting lower roughness rates instead.Fundação de Amparo à Pesquisa do Estado de São Paulo (Fapesp)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Capes)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Building cluster and shading in urban canyon for hot dry climate - Part 1: Air and surface temperature measurements

Under low latitude conditions, minimization of solar radiation within the urban environment may often be a desirable criterion in urban design. The dominance of the direct component of the global solar irradiance under clear high sun conditions requires that the street solar access must be small. It is well known that the size and proportion of open spaces has a great influence on the urban microclimate This paper is directed towards finding the interaction between urban canyon geometry and incident solar radiation. The effect of building height and street width on the shading of the street surfaces and ground for different orientations have been examined and evaluated. It is aimed to explore the extent to which these parameters affect the temperature in the street. This work is based on air and surface temperature measurements taken in different urban street canyons in EL-Oued City (hot and and climate), Algeria. In general, the results show that there are less air temperature variations compared to the surface temperature which really depends on the street geometry and sky view factor. In other words, there is a big correlation between the street geometry, sky view factor and surface temperatures

Building cluster and shading in urban canyon for hot dry climate Part 2: Shading simulations

Under low latitude conditions, minimisation of solar irradiance within the urban environment may often be an important criterion in urban design. This can be achieved when the obstruction angle is large (high H/W ratio, H = height, W = width). Solar access to streets can always be decreased by increasing H/W to larger values. It is shown in this paper that the street canyon orientation (and not only the H/W ratio) has a considerable effect on solar shading and urban microclimate. The paper demonstrates through a series of shading simulation and temperature measurements that a number of useful relationships can be developed between the geometry and the microclimate of urban street canyons. These relationships are potentially helpful to assist in the formulation of urban design guidelines governing street dimensions and orientations for use by urban designers

Numerical Simulation of Effect of Urban Geometry Layouts on Wind and Natural Ventilation Under Mediterranean Climate

The use of the method "simulation" of the microclimate for an urban site presents much of interest, because this can serve as us observation and analysis of the consequences of various scenarios relating to the existence and the importance of the constituent elements in urban space. Wind in outdoor urban space is among the most difficult parameters to identify and control field given its instability. Currently, in the field of the ventilation, there are some outdoor spaces simulation tools, used to assess the flow of the wind at different spatial scales. The aim of this research is to demonstrate the effect of the urban geometry of the layout on the wind movement and the outdoor natural ventilation. However, this study investigated the effect on outdoor thermal comfort of a building layouts in a planned residential area situated in the city of Jijel humid Mediterranean region of Algeria.  In order to improve outside comfort in this open space, a 3D numerical simulation tool ENVI-met 3.1 beta 4 was used to simulate the urban thermal climate taking into account various scenarios. Thus, simulation's results are discussed in this pape

The Influence of Albedo on the Urban Microclimatic Street Canyon

In city, when temperatures run higher than those in suburban and rural areas, this generate a phenomenon called Urban Heat Island (UHI), this effect  occurs, primarily because growing numbers of buildings have supplanted vegetation and trees. The main causes of the different microclimatic conditions in cities are linked among other parameters to urban geometry which influences incoming and outgoing radiations as well as surface material properties, such as color and texture. In hot climates the elevated surface temperatures of materials directly affect, not only the urban microclimate, but also thermal comfort conditions in urban open spaces. In order to evaluate the microclimate variation of urban street canyon compared to the variation of walls and ground surfaces materials, series of field simulation are used by software tool, Envi-met v3.0, in down town of Constantine, Algeria