Page 99 - New Trends in Green Construction

New Trends in Green Construction
STUDY OF TWO VARIABLES ASSOCIATED WITH THE RADIATIVE EXCHANGE OF WINDOWS AND THE DEGREE OF VISUAL COMFORT
Marta M. Varo-Martínez, José Ramírez-Faz, Rafael López-Luque, Luis M. Fernández-Ahumada
Keywords: Daylight and solar access; Sky Vision Factor ; Sky Opening Index 1. Introduction
In order to develop the energy audit of existing buildings, effective devices and procedures are required to evaluate the potential for solar accessibility of openings and windows. Window insolation is related to solar gain, the potential for natural lighting or the need for sun protection. The Sky View Factor (SVF) index or radiative exchange factor between the window and the open sky is used for its characterization. As an indicative parameter of psychological comfort, the Sky Open Index (SOI) is used, or solid angle with which an observer can appreciate the sky being in the center of a window. Published methods to characterize these indices require extensive geometric characterization of solar obstructions (Alzoubi and Alshboul, 2010; Compagnon, 2004; Gómez-Muñoz, 2010). In this work it is shown, by the means of a practical case, the suitability of use of the device LRTV, to determine them and to be able to interrelate them.
2. Methodology
The Light Ray Tracing and Visioning (LRTV) device consists of a flat platform with a hemispherical mirror. An arm, which is perpendicular to the platform, enables to hold a conventional camera by placing its optical axis perpendicular to the platform and coinciding with the center of the mirror. In order to enable the correct levelling and alignment of the lens plane with vertical (windows) or horizontal (skylights) faces, three levels of bubbles are arranged in this section. Figure 1(a) shows a photograph device. This device has a disadvantage, that is, in a hemispheric photography the camera and the device arm will appear, however, a correct interpretation of the image allows to obtain useful images in all cases.
Figure 1. (a)LRTV device; (b)Window imaging
3. Results of the building of the Faculty of Philosophy and Psychology of the University of Seville (Seville, Spain)
The results will be presented f o r the building shown in figure 2. There are S-W facing walls with azimuth 19.8o S-W and N-E facing walls with azimuth 109.8o N-E, highlighted in red in figure 2.
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