We bought this cool Coleman 54 Qt. Stainless Steel Cooler a couple of years ago for a big road trip.
This cooler was in the bed of the pickup truck all the way from San Diego to Bozeman Montana and back and it did a fine job. But... there was one problem.
Sitting in the summer sun all day, the steel top would get really hot, too hot to touch. And the inside of the top would be warm. There is space for a shelf or a rack in the cooler, and we had put a baking sheet there, so we could store stuff above the ice that we didn't want to get wet. The problem was that shelf would stay too warm because of the heat radiating from the top of the cooler. Additionally, the baking sheet blocked cool air flow from the cool ice below.
So, what to do?
First I considered painting the top of the cooler white or putting some kind of insulating sheet on the top of the cooler.
But then I read about radiant barriers and how they worked and I decided that was exactly what I needed.
I used special GE Silicone Sealant for plastic sheets and other plastics to glue 3 layers of InfraStop Double Bubble Reflective Foil Insulation to the inside of the cooler lid. (I first tried regular sealant and it didn't stick, be sure to use the special stuff for plastic sheets.) Also, I was very careful to completely seal the edges of the sheets so that nothing can get in there and the cooler remains easy to hose out and clean. We will have to use a little care to not cut or tear the insulation on the inside of the lid.
Note that it took a long time for the sealant to completely dry and stop smelling. I put sealant under the insulating sheets and between each sheet and I suspect it is pretty air tight in there... so even after a week if the cooler was closed for a while you could smell sealant when you opened it. But after a couple weeks of leaving the cooler open that went away.
Then I got two small baker's sheets to use as a shelf inside the cooler, instead of one big sheet. We will try to use just one so there is plenty of room for the hot air to sink and the cool air to circulate above the shelf. But just in case we want to use both sheets, I put six 1 1/4" holes in each sheet. Maybe that will help.
It's not to hot yet here in San Diego, but on a recent sunny trip to the desert with mid 80 degree F temperatures the inside of the cooler lid did stay cool. We will see how it really works this summer.