Any fancy fooker also put sprinklers up on top of their alu-zinc roof to keep the place nice and Scandinavianish during hot seasons? I presume the painted alu-zinc sheets don't rust and any run off that doesn't evaporate goes into the guttering. Would make a diffo to the temp inside the house?
It's got a ridge down the middle so the sheets are approx 5.5m each side. Expansion shouldn't be an issue right?
I also believe that they cool down a lot faster once the sun goes down as they don't hold the heat like roof tiles do.
I've been wrong before.