Use anti-con insulation it will save you having to put up an extra lining. It is normally put up with a wire mesh to hold it in place before you put the sheets on. I used it in my shed and it works fantastic. The silver also reflects the light lot better. The sliding doors I used 25mm polystyrene with silver paper stuck over the top. The air conditioner now has no problem keeping the shed nice and cool and it completely stopped any condensation in the shed. There was a lot of the old roof insulation stuff going cheap after the govt roof insulation scam. The problem with using this is it will need to be lined after which may end up costing a lot more as well as being a lot more work. Have fun with the flat pack shed, keep us posted as I'm sure you will.
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