Improvement of thermal insulation performance of transparent vacuum insulation panels and in-situ performance test

Reducing the energy consumption of buildings, factories, and other facilities is essential to achieving decarbonization. In order to reduce the energy consumption in the residential houses and commercial buildings, Zero Energy Buildings (ZEB) and Houses (ZEH) have been defined in Japan. Then efforts are underway to make buildings ZEB or ZEH. However, energy-saving technologies have not been introduced in existing buildings, especially insulation performance is insufficient. In order to retrofit the insulation of existing buildings, transparent vacuum insulation panels (TVIPs) using structured cores for window insulation retrofit of existing buildings are proposed. The TVIP is produced by inserting the structured core, the low-emissivity film, and the adsorbent into the transparent gas barrier envelopes and vacuum-sealing them. Although the TVIP has the advantage of being inexpensive, lightweight, and easy to install for insulation retrofit, it had a major challenge of outgassing from the core material after vacuum sealing. However, the thermal conductivity of the vacuum layer after vacuum sealing in TVIP was successfully reduced to less than 0.008 W/(m • K) by reducing outgassing from the core material. In this paper, the authors introduce the fabrication process of the prototype TVIP and the results of the thermal conductivity measurement. In addition, the authors carried out the In-situ performance test of TVIP, in which TVIP was installed on the double layer window glass and the surface temperature and the heat flux were measured. The result shows that U-value of double layer window glass with TVIP was reduced from 3.4 W/(m2K) to 1.0~1.5 W/(m2K).