yes, that's what it's supposed to be, I also want to install an infrared heater, in case you want to tinker with something or drink a barley juice with your buddies, but nothing more than that
Then I would leave out these expensive things. The foil, insulation, etc. really cost a lot of money and if so, everything would have to be insulated equally, otherwise the heat would just escape somewhere else. I was just in my garden shed and would see no advantage in such a complex structure for the usage you mentioned.
Well, my dad said in summer the structure offers some protection from heat, I would put 160mm into the rafters. OSB for the inside is already in the house. I would still need to get insulation.