There is a movement in the roofing industry toward what is referred to as “single ply” roofing for flat roofs.
This energy efficient roofing is like a big (usually white) rubber roof. It lasts longer than hot tar roofing and is much superior across the board. This product has been around since the sixties or so and has been upgraded and changed and re-invented. It now is a standard in the industry and becoming more popular as people get introduced to it.