Yes, the floor is concrete, over a layer of 2" hard foam insulation. Since I am in the high desert, it is important to keep the house cool in the summer as well as warm in the winter. In fact, keeping it cool is more important, because supplemental heating is a lot simpler than supplemental cooling (as Jack has noted several times).
My thermometer is on the opposite side of the wall you can see, so it's not being hit by direct sunlight.
The top window does not open, although that's a design flaw that I do regret. I may change it out to a window that will open later on.