Thermal transfer
Here's a pic I took last night that demonstrates thermal transfer. The outside skin on my big truck is Diabond which is .020 alum, 3mm polypropylene, .020 alum skin, it has a thermal value. It is held on with 3M tape onto 2" aluminum so no real metal to metal connection, there is 2" high density polyurethane spray foam in the walls, interior is completely lined with 3/8" plywood, and 1/8" Luan. The temperature dropped fairly quick last night and you can see where every stud is as the heat difference from the interior is radiating out through them, the temperature differential between the outside and the inside is only about 5 degrees. This camper does a really good job of keeping warm in the cold the way it is built, and it does have what could be considered a thermal deficiency.
Here's a pic I took last night that demonstrates thermal transfer. The outside skin on my big truck is Diabond which is .020 alum, 3mm polypropylene, .020 alum skin, it has a thermal value. It is held on with 3M tape onto 2" aluminum so no real metal to metal connection, there is 2" high density polyurethane spray foam in the walls, interior is completely lined with 3/8" plywood, and 1/8" Luan. The temperature dropped fairly quick last night and you can see where every stud is as the heat difference from the interior is radiating out through them, the temperature differential between the outside and the inside is only about 5 degrees. This camper does a really good job of keeping warm in the cold the way it is built, and it does have what could be considered a thermal deficiency.