Mass transfer modeling in gas barrier envelopes for vacuum insulation panels: A review

A vacuum insulation panel (VIP) is a very efficient thermal insulation system for buildings. It is constituted of an evacuated porous core material, enveloped in a gas barrier membrane. The total conductivity measured is as low as 5 mW/(m K). The high performance is due to the low pressure inside the panel and the gas barrier envelope plays a key role in maintaining the vacuum during the whole VIP service life. Indeed, due to the permeation of atmospheric gases through the envelope, a slow increase of pressure and humidity occurs over time, which involves a thermal conductivity increase in the mean time. This review paper details the mass transfer models used to predict the permeation rates of gases through the VIP envelope. The sorption–diffusion model for gas permeation through polymer membranes is presented as well as alternative permeation models. The parameters which play a key role for mass transfer are detailed. The adaptation of the permeation models from homogeneous polymer membranes to multilayer gas barrier membranes is then presented, including an important section about metal-coated polymer films. The conclusions of the works based on several approaches are reported.

► A review is conducted on mass transfer modeling in vacuum insulation panels.
► The focus is on multilayer membranes with metalized polymer films.
► Sorption–diffusion model is used for gas permeation through barrier envelopes.
► Very low permeation rates are due to the metal coating on polymer films.
► Permeation through the metal coating is a defect driven process.