Lighting and Energetic Characteristics of Transparent Insulating Materials: Experimental Data and Calculation

Abstract

This paper reports the study of thermal and optical properties of innovative transparent insulating materials (TIM) for glazing systems: silica aerogel (pane and granular) and capillary geometric media. Twenty-one samples were assembled with several kinds of glasses in various combinations with TIM. Transmission and reflection coefficients versus wavelength were measured and the results were elaborated in compliance with UNI EN 410/2000. The better performance was given by the monolithic aerogel both for light transmittance (0.58 in interspace between two 4mm float glasses) and thermal insulation (U = 0.63 W • m— 2 • K—1). The solar factor was 0.70. The performance of the innovative glazing systems was compared with data related to windows normally used in Italy and in EU countries, in order to comply with the limits of the local normative standard required for thermal transmittance. The results showed a very promising behaviour of TIMs, in fact a 60% reduction in heat losses with respect to a double glazing with a low-e layer was achieved, with only a 27% reduction in light transmittance. For the granular systems, a U-value little higher than 1 W • m—2 • K—1 with the same total thickness was obtained, even if the light reduction was about 66%.