On a vehicle you would call it a tropical roof. I have seen them on Land Rovers and MCI buses that were in service in Saudi Arabia. Basically just a second roof skin with maybe an inch airspace between roof skins, you just need some sort of aluminum or steel rib every foot or two to support the second roof. On the MCI bus I saw it at a show in the USA after it had been returned to the States and compared to other buses on exhibit that day it was noticeably cooler.
IBA #7552 - SS1K in 2000 and 50CC in 2002
In the Uvalde, TX area and always willing to help travelers escaping into Mexico.