Technically, yes, we can do this. There are practicality issues to deal with. If you use trees to mark your fire perimeter, what do you do if a tree burns down?

Technically, yes, we can do this. There are practicality issues to deal with. If you use trees to mark your fire perimeter, what do you do if a tree burns down? They can catch fire from on top just as easily as from on bottom. probably more so as every time I've ever seen the aftermath of a forest fire it's always been left as stumps. Then, there's structural rigidity, deployment times, and the sheer mass of material people would have to deploy to make a firewall like this work. You would need something like an 18 wheeler stuffed to the brim with this foil and support beams to stave off a football field worth of space.