I was just reading this link and I was wondering what the Physics behind this 5°C temperature drop is.
On this website, they describe a passive cooling system being used in a part of Bangladesh. For this system, they take recycled bottles and a sheet of cardboard. Holes are cut along a grid in the cardboard to fit the neck of the bottle. The bottles are cut somewhere near the middle to be a sort of funnel, with the neck going into the hole in the cardboard.
I can't help but wonder if the temperature change in the room is due to circulation, and not any temperature effect. However, if air is flowing between the outside and the inside, then some heat energy may be converted to kinetic energy.