Not only outstanding insulation performance but also the extended service lifetime is required in vacuum insulation panels (VIPs). Thermal insulation performance of VIPs is degraded with time due to deterioration of the inner vacuum. The main causes are gas permeation and out-gassing in VIPs. Especially, gas permeation in the lateral through heat-sealed flanges has the largest effect. It is thus necessary to investigate the permeation characteristics of the envelope seal materials (linear low density polyethylene, LLDPE, and low density polyethylene, LDPE). A measurement apparatus using multiple radial permeation passages surrounded by the permeation gas jacket is designed to measure the gas permeation rate through the polymer films. The measurement shows reliable accuracy compared with other reported results. Further, to reduce gas permeation through the heat-seal, a novel method of employing metal wire the heat-sealed layers is also investigated in this study.