Abstract: Air permeable core material is vacuum sealed in enveloping member. Further, core material is formed of at least two layers of heat insulating core materials having different heat conductivities. Further, at least two of the at least two layers of heat insulating core materials which form core material are formed of materials having change gradients in the heat conductivity changed in accordance with temperature, and the change gradients in the heat conductivity of the heat insulating core materials intersect with each other. Since two layers of heat insulating core materials having different heat conductivities are provided in a vacuum state, a heat insulating property becomes higher compared to a conventional configuration in which a single layer of the heat insulating core material formed of fiber material such as glass wool or rock wool is vacuum sealed and the high heat insulating property is shown in a wide temperature range.

Abstract: Air permeable core material is vacuum sealed in enveloping member. Further, core material is formed of at least two layers of heat insulating core materials having different heat conductivities. Further, at least two of the at least two layers of heat insulating core materials which form core material are formed of materials having change gradients in the heat conductivity changed in accordance with temperature, and the change gradients in the heat conductivity of the heat insulating core materials intersect with each other. Since two layers of heat insulating core materials having different heat conductivities are provided in a vacuum state, a heat insulating property becomes higher compared to a conventional configuration in which a single layer of the heat insulating core material formed of fiber material such as glass wool or rock wool is vacuum sealed and the high heat insulating property is shown in a wide temperature range.