Fachada de vidro: reflexos da luz natural em uma cidade dos trópicos

Abstract

The curtain wall is a widespread glass facade system in architecture from the international aesthetics of the Modern Movement to contemporary times. The glazed building model has spread around the world based on air conditioning artificial technology, ignoring the cultural and climatic characteristics of the destination’s site. For the hot and humid climate of Maceió it is important to know well the parameters and variables that influence the performance of this type of envelope for an adequate architectural project. The general objective of this doctoral research is to evaluate the reflections caused by glass facades of vertical buildings in daylighting in the tropical city of Maceió, Alagoas, Brazil. To achieve this main goal, the following specific objectives were accomplished: identification of the impact of natural light reflected from different geometries of glass facades on the internal illuminance of the neighboring front building; analyze the variation of reflected light as a function of the angle of incidence in the different types of facade glass; evaluation the impact of the glass facade on natural lighting outside vertical buildings in parameterized urban block arrangements. The methodology was created from a critical review of literature on glass facades with justification of the adopted problem. From the analysis of the use of the glass facade in the city of Maceió, canyons and urban blocks were modeled based on the Construction Code and Master Plan of the city. The simulations were carried out in the Troplux program, the transmittance and reflectance measurements of the types of glass were carried out respectively on a digital spectrophotometer and experimental assembly of equipment (light source, lenses, iris, goniometer and luximeter) on a pneumatic table. Measurements were performed for angles from 0 to 90 ° with an interval of 5 °. The results showed the great difference that reflectance can have depending on the shape, the type of glass and the urban configuration that favors a greater angle of view of the sky. That is, for the same land and building in which a façade from flat geometry is changed to concave, convex and prismatic, the surface area increases, thus increasing the amount of reflected light. The clear sky provided higher illuminance values while the partially cloudy sky represented greater uniformity of results and significant reduction. The times between 9:30 am and 3:30 pm are the times when the reflectance increases the value exponentially, diverging from the manufacturer's specification and international glass database for softwares that indicates the value only in perpendicular incidence. Transmittance also reduces inversely, at times when the use of natural light is most needed for activities inside the building. It is expected to contribute from technical regulations that consider the reflectance of glass in the insertion of new buildings as well as the evolution of the city's bioclimatic architectural repertoire, valuing the identity, culture and sustainability of the envelope systems with less energy demand in the city. Tropical weather.