## 1 Introduction
Furthermore, the estimated R\({}_{\mathrm{a}}\) color rendering index is lower than the one of a double glazing system with air (R\({}_{\mathrm{a}}\) = 98) and a value of 92 is reached for a window with monolithic aerogel 14 mm thick [12]. The influence of monolithic aerogel windows on the heating energy consumption was evaluated also through simulations for a typical single-family house in Denmark [13]. An aerogel glazing (20 mm aerogel thickness, U-value 0.5 W/m\({}^{2}\)K and g-value 0.75) was compared to a triple-layered argon-filled glazing with two low-e coatings (U = 0.6 W/m\({}^{2}\)K and g = 0.46): the annual energy saving was about 1200 kWh/year (-19%). [PERSON] and [PERSON] investigated the influence of glazing systems on the energy performance of a multifunctional building in six different cities (Rome, London, Moscow, Helsinki, Ottawa, and Beijing) [14]. Both conventional and innovative glazing systems with a silica granular and monolithic aerogel in the interspace were considered. Windows with monolithic aerogel result as the most efficient systems for cold climates, with a reduction of the annual energy demand of about 22-27% (Ottawa); on the contrary, the energy demand for cooling increases, especially in temperate climates, due to the high solar factor of aerogel windows. [PERSON] et al [15] investigated the energy saving potential of an office building with an aerogel windows in a hot and humid climate (Saudi Arabia); the silica nanogel glazing allows a saving of about 16% in the annual energy consumption, when compared with conventional double glazing. Results were confirmed by [PERSON] et al. [16], who carried out dynamic energy simulations with a translucent aerogel granulate system in an office facade. The translucent spandrels (14 mm granular aerogel in the gap between two 4 mm float glasses) reduce the energy demand in mixed and cooling dominated climates, namely Tokyo and Singapore, with respect to a double glazing facade. The novel interest in monolithic aerogel glazing systems is justified by the rapid production process, able to reduce costs and waste [6; 7]. In this context, the aim of the present paper is the evaluation of the energy performance of a new double glazing system with monolithic aerogel in the gap, in a non-residential buildings application. To this aim, the thermal characterization of the sample was carried out and its behavior in a very glazed building was simulated in different climate conditions. The aerogel used for the fabrication of the prototype is obtained with the Union RSCE process, in which a mixture of chemicals is placed in a mold within an industrial hot press [6]. This is used to seal the mold, to heat its contents to a supercritical state, to controllably release the supercritical fluid, and then to cool the mold to room temperature. It is possible to obtain samples of maximum dimensions equal to 140x140 mm in only 6.5 hours by using a laboratory press (267 kN). The measurement results were implemented in a dynamic building simulation model in order to compare energy demand with the one of standard solutions. The novelty of this study consists of the characterization of a very new kind of aerogel, by considering many different aspects of its potential qualities. An original sample was specifically developed and built in the laboratory and it was, therefore, used for the experimental and numerical analysis.