Discovered that the attic access hatch isn’t insulated, which honestly isn’t surprising given when it was built. No ladder system. I’m working on cutting up some foam boards to glue to the backside. Hopefully it will reduce how much is radiated through this barrier.
These thermal imaging cameras don’t have specific temperature for each color. The hottest area in view will always be at the extreme white/yellow end of the graduent, and the coldest will be at the black/purple end. Even with more insulation in the attic, the hatch will likely still be this color. That is, unless the hatch was more insulated than the ceiling, or it was colder in the attic than the room this photo was taken from.