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I have a bit of a problem in my workshop, in that the dark grey, "insulated" roller door works as a very effective radiator, heating the workshop up a great deal. It faces near enough South, and gets very warm, so warm that when standing next to it inside, with the door down, it you can feel the heat being radiated from its surface. I can't change the external appearance (I had a struggle just to get approval for the door, as it is directly opposite a Grade II listed building) so whatever I do has to be inside. I don't need to open the door very often, as most of the time I use the side door. So, what I'm thinking of doing is to buy some multifoil "insulation", and make up an internal roller blind. I have some lengths of alloy tube, including some fairly big (4" diameter) stuff. There's around 300mm of so of room at the inside top of the door to take the rolled up blind. Rather than have the blind roll around the tube at the top, I'm thinking along the lines of having it rolled around the tube at the bottom, with some nylon tapes run via pulleys, so that the blind will roll itself upwards, lifting the tube as it goes (we used to have a bamboo blind that worked like this). I know that it's pretty poor insulation, in terms of thermal conductivity, but multifoil is very good at reflecting out long wavelength IR, so it is ideal for keeping radiated heat out. As the roller door isn't at all well insulated (the slats are around 20mm thick aluminium extrusions, filled with foam) and as the door is full of high conductivity thermal bridges, I'm hoping that reflecting heat back towards the door will result in it heating the door up and so increasing the outward heat flow. I can't easily seal the edges, but could add some boards either side that the multifoil blind could sit against, and if it were trapped under a batten at the top that should seal that area up OK. The questions are, firstly, will multifoil tolerate being wrapped around a tube and rolled up and down? I suspect it may do, as it's basically just alumised mylar (as used in "space blankets") with some think polymer fleece material between the layers. The second question is how best to join sections of the stuff together. I need to make up a 3m wide blind, and the widest rolls seem to be around 1.5m or 1.6m. I don't trust the sticky tape, as I doubt that it will tolerate being wrapped around a roller, so perhaps I need to look at using an overlapping multilayer approach, a bit like slates on a roof. Anyone any thoughts?