Hi @thebakery
I think the best insulation is Foil board (below) for sheds as it blocks most heat and is moisture proof/barrier and create an air gap between the shed wall and inner frames, The air gap is crucial to disapate most condensation forming on the inside of a shed wall. Many people put a layer of ply 10mm over the inside of the shed frame work as an inside wall.
So the shed wall looks like first the tin wall then , air gap, then foil board between the frames then plywood over the inner walls. I would glue foil board to ply sheets so its one wall piece, The air gap circulates air and helps disapate condensation, The air gap also insulates, the foil board stops moisture and insulates the ply also insulates.
The frame of the shed will conduct heat from the outside through to the metal inside so the ply over it will help block that conducted heat too.
Heat transfers in different ways
1 Radiant heat like when you to close to a heater it burns to the side.
2 Conduction The sun on one side of a metal door will heat up through the metal and transfer on a lesser scale inside.
3 Convection where the air above the heat source warms the air upwards and it circulates around an area and cools until it is reheated from radient or conduction source again
So @thebakery the foil insulation you meantion is very good at blocking Radiant heat in the roof and walls where it also has a air gap to slow convection heat transfer. But it only has a low level of polyester blocking conduction heat through the middle it dose work to a degree.
I bought and imported a thermal heat shield with plastic it is very similar to what they use in space craft and sewed it into my curtains (it works very well summer or winter.) at the windows as curtain material creates a thermal break combined with heat trapping top pelmet and making a natural closed air gap. any how thats my little side experiment.
Foil board comes in different sizes and quantities,
Foilboard 10mm x 2400mm x 1200mm Standard 10 Insulation - 10 x 2400 x 1200
Now consider Foil board it has the reflective silver on two sides Keeping radiant heat out and in at winter time (Radient heat stopped) with a sandwich of foam in the middle that creates a thermal break from on side to the other all but stopping (Conductive heat transfer).
Because the inside of the foil remains cool there is low convection heat. So it will work better in the walls too. as well as provide a moisture block.
