I have been contemplating a very sustainable desert community. They could save lots of money and time if they built dwellings out of used cargo shipping containers. But how to keep them cool in the desert? Green Roofs.
The shipping containers would be cheap. They could be cleaned and refurbished to become modular housing components. And by putting a green roof on top, they could keep the dwelling in the cool shade. The containers would have the structural strength to support a green roof since they were designed to be stacked like blocks.
Building soil filled planter boxes on the sides would provide further shade, some insulation, and even thermal mass effects. That last aspect is where the sheer volume of dirt would keep the dwelling cooler during the hottest part of the day and warmer at night.