Geoff, the shading I use is knitted, black shade cloth on the outside. Friends with money than me use the Aluminium foil stuff. I've tried Green cloth but found the plants didn't grow well under it nor was the flowering good. (Cymbidiums mainly). It seemed to work ok for Garden plants. On the inside I use clear Polytunnel or UV treated polythene sheeting to hold warmth in winter. Too hard to remove for summer. I have friends that use UV treated large bubble plastic as insulation, which is really good, hard to get & expensive.