Concept and Performance Analysis of a Biodegradable Glass Film for Energy Efficiency and Daylighting Control

Windows are essential building envelopes but often contribute to building energy consumption due to the direct solar heat gain. Retrofitting windows with glass films presents a simple yet effective energy-saving measure. However, conventional glass films pose environmental challenges post-disposal due to their non-biodegradability. In response to this issue, this paper proposes a degradable glass film utilising polylactic acid as the matrix material and incorporating pore and SiO2 as fillers. Initially, through Mie theory, the film's microstructure was optimised. The results indicate that the film achieves optimal solar transmittance and mid-infrared emissivity of 0.661 and 0.955, respectively, at a thickness of 100 μm, with a pore diameter and porosity of 9 μm and 6%, and SiO2 diameter and fill ratio of 10 μm and 20%. Subsequently, based on the optimised optical properties, the cooling load and daylighting performance post-application of this film were assessed. The calculations reveal a reduction in annual cooling load by 27%, with the percentages of time with acceptable glare level and illuminance uniformity increasing by up to 36% and 91%, respectively. The proposed concept opens new avenues for research of degradable glass films, presenting a promising direction for the advancement of sustainable building materials.