i used lizard skin sound control + ceramic insulation spray on the floor and halfway up the walls, along with the engine side of the dog house. very noticeable difference in both sound and heat. my feet rarely get hot now while driving barefoot or in sandals. and once you get the temperature how you want, it holds at that temperature longer as well.
While sleeping in the van the other week at about 10k ft it got into the 30*s at night, and sleeping in a summer sleeping bag 40-50*+, i slept great and comfortable until i had to use the restroom in the morning.
where the windows would have been (i have a cargo van) i taped up reflectix, and then on the ceiling, i cut out and taped up a sheet of 3/4" foam insulation board. the only other liner installed is a bed rug carpet kit.
I plan to stuff the openings around the wheel wells with the usual pink insulation, and then line the walls with it and cover it with some plywood walls.