During the Generator workshop I had an urge to cover my head, and had some aluminum tape around. So I just joined it, by removing the protective foil from places where I wanted it to stick. It was a super quick job, and the result was far from high fashion, but the effect was chilling. I even thought I could get cold because of such a difference between my face and the top of my head. It felt like wearing air conditioning.
My guess is, that a few factors luckily fell together. Firstly, of course, the reflectivity, which bounces most of visible spectrum away. Then I expect that material itself meant a lot: alumunum is very effective at transfering heat, so untill my body is hotter than environment, it should take heat off me and transfer it to the air. Lastly, I guess, the empty space below the hat (this time I do not refer to my brains 
) did a good job: it was in constant shade and well ventilated through wide narrow gaps.
And another neat side-effect: I finally had a real, actually useful tinfoil hat! Even if it doesnt provide full protection from all the zucks, it still works well.
I hope to build some more of them this summer, maybe with more design ambitions too. Fashion design here does have big possibilities, which strangely arent used much at all.
