Help! Water in waterer gets too hot in this 100+ weather

[Coop de Grass]

Sorry to bump an old thread, but this is exactly the kind of solution I was looking for. I have a connected coop and run, but I would like to put the waterer and feed in the run for easy access. I was concerned about the waterer getting too hot, but a reflective material would probably do the trick. Anyone tried this and know how it holds up in the weather? From what I am finding, this radiant barrier material is made to go inside a roof.

So glad I found this post. Would this work with a rain barrel? I need to be able to keep 20 hens watered for 2 weeks- neighbors will check every other day. I was going to use a gravity fed system. Any suggestions on the best type of system would be helpful. The chicken fountain? the cup watering system from McMurray?

Help!