The image below was taken by Matt Schwoegler, a thermographer and infrared instructor with the Snell Group. Matt was on location in Vermont, helping to train a weatherization crew from the Champlain Valley Office of Economic Opportunity (CVOEO) which was already working on the home. The room in question was used by the homeowner as a three-season porch/bedroom. Matt explains that this portion of the home appeared to be an addition to the original structure, and was likely moved to the home's location where it was connected to the main house.
During the infrared training and building inspection, which was taking place in warm weather conditions, Matt found what appeared to be an insulation level on the wall in this room. While the ceiling appeared to be uninsulated, what was happening with the wall was not as clear.
So, what's wrong with this picture?
Key is this was done in warm weather. The back wall of the room was also uninsulated, but the lower portion was against the air-conditioned envelope of the home. The red area above was against the attic area, causing the increase in temperature.
Warm weather conditions is pretty relative and for Vermont 75 degrees F can easily be seen as warm weather, not to mention the fact that many VT homes don't use air conditioning. If the porch was an addon with an uninsulated roof then we can probably assume there are some air leaks causing cooler interior air to be drawn to the space from the opening to the house. If the main house has insulated exterior walls, which in VT I assume it does, than AC cooling is probably not the culprit or the cooler walls. If there is humidity from lack of a conditioning unit then the cedar walls are probably absorbing moisture and as the air moves along them, evaporation will cause the walls to cool. The hotter roof can easily be from solar radiation or a mini stack effect from the uninsulated and non vapor sealed roof. I do see a couple hotter spots on the side walls though, which leads me to believe that the temperature difference is purely solar radiation, and most parts of the exterior porch walls are shaded.