On the impact of hollow silica powder on the performance aerogel glazing systems in buildings: Results from laboratory and simulation analyses

Aerogel-based glazing systems are an effective solution to reduce space heating energy use in buildings, even if overheating risks in temperate climates exist due to the high solar transparency of the systems. This study analyzes the potential of an innovative solution, based on a mixture of granular aerogel and hollow silica powder, in small concentrations, to increase the reflectance of the aerogel layer and reduce solar transmission. A set of glazing samples, different in aerogel layer and powder concentration, were produced and test in laboratory to determine the relevant solar and thermal properties. It was found that at 7.5 % powder concentration the solar and light transmittance were reduced up 0.48 and 0.45 in a 0-1 scale, respectively. Analogously, the solar and light reflectance increased up 0.49 and 0.46, respectively. The thermal resistance of the system increased up to 0.18 m(2)K/W, peaking at 1.88 m(2)K/W for the 34 mm aerogel layer sample. The thermo-physical properties were used as input to simulate an office building in different climatic conditions; it was found that the proposed technology ensured total energy savings for 4 % powder concentration and higher; cooling energy savings were up to 21 % and total energy savings up to 21 %.