While browsing the Weird Wired World for shades to hang over our terrace, I came across a few that claimed to be insulation. Like this one on amazon. At least they claim to be 断熱 dannetsu, which I've always translated as insulation. Maybe this is just a bit of a false friend and the meaning of the Japanese word is wider, but I think it's just another example of thermal ignorance, which transcends linguistic, as well as national and cultural borders.
The shades--bits of fabric to stretch out in front of windows or over terraces--are certainly going to be stopping radiation and cutting ultra violet. To put it more precisely, I should just say that they will stop radiation, as UV is a kind of radiation. That's what the websites were saying, though. 遮熱 shanetsu is the Japanese word for thermal shielding, but I'm not completely sure if that is the English word for it.
Hanging a piece of fabric in front of your window is going to have very little insulation effect. For a start it's not really thick enough to insulate. You don't see many people heading out on a cold winters day holding a plastic sheet next to them to keep the heat in, although of course it would be better than nothing. Even if it were insulating, the fact that it's hanging a few centimetres away from the window, or stretched out at 60 degrees to the window, means that any insulation effect will be severely compromised by the hot air sneaking around the sides.
