This was originally posted in another thread, I'm reposting it here so its available where everyone can find it.
There is a solution for the tent-end when its very hot or cold. I'll preface this by saying that I don't think you'll need it. The A/C and heater in the 'pod are oversized for the job and could easily keep a trailer twice the size of the 'pod cool or warm. In my popup we only had a problem when we were in direct sunlight above 90F, or below 40F.
If you do have a problem, you can go with a commercial solution or a homemade solution. In either case the solution is a "radiant barrier", basically aluminum foil. You can try Popup Gizmos for an easy and well-respected solution used in the popup world. You can also buy a roll of radiant barrier (either foil or bubble-wrap type) and cut a sheet to size. Drape it over the top and clamp it down with spring clamps. One problem with the foil type is constant movement from wind can make holes in the barrier and also rub some foil dust into the tenting.
We only used this during early-season trips when it dipped into the 30's, or during our annual trip to the beach. Most other times we were camped in the shade or it was cool enough even in the sun.