An integration assembly for a battery pack mounted between the passenger cabin floor panel of an electric vehicle and the driving surface is provided, the assembly utilizing a multi-layer thermal barrier interposed between the battery pack enclosure and the passenger cabin floor panel, where the multi-layer thermal barrier provides noise isolation, thermal isolation and vibration damping, and where the multi-layer thermal barrier is compressed when the battery pack enclosure is mounted to the vehicle. The multi-layer thermal barrier is comprised of a first layer formed from a compressible and conformable elastic material and a second layer formed from a conformable thermally insulating material. The multi-layer thermal barrier may also include a moisture barrier layer that encases the first and second layers, for example a moisture barrier layer fabricated from a plastic. A sealant may be used to seal and bond the moisture barrier layer to the battery pack enclosure.