I recently purchased the XD 1500. So far, my young son and I have insulated the front fender sidewalls, the roof, both tunnels, and all four doors. We attempt to add one to two layers of sound-deadening mat, followed by a layer of insulating foam where space permits.
The next project will be to insulate the back wall, which is a significant source of noise and heat. Although I haven’t examined the dash extensively yet, I intend to remove it to insulate the front wall.
The pictures illustrate the removal of the driver’s front fender, some of the problematic areas, and our insulation efforts. The red circles indicate the open spaces between the cab and the outside air.
The insulated pictures are from the passenger side project.