Fabric that lets light energy through, then retains the heat? Snake oil?

Interesting concept having the translucent outer layer, I can see the theory but have no idea of course if it actually does anything in practice! Would like to see some test data.

Also, it'll only work when it's both cold and sunny, so useless most of the time in the UK regardless!

Its perfectly feasible. In a normal jacket, the insulator traps air, and the air heats up with the short wave radiation that your body emits. If its black or dark coloured some of the long wave radiation the outer layer of the coat absorbs will also contribute to the warming of the air. If its light/white most of it is refected away, so you're totally reliant on your own body heat. What they're doing is basically a greenhouse. The outer layer (and the insulation) allows long wave solar radiation to pass through it, which then hits a long wave sensitive layer, that warms, and radiates back short wave radiation which the air in the insulation absorbs, producing a warm layer around your body (just like a greenhouse), as well as warming you directly.

The problem of course is that sunny days when this will be effective tend not to be the ones you're freezing your ass off on.

Translucent outer layer..... so it's a bit like a green house then.

https://en.wikipedia.org/wiki/Maxwell%27s_demon

Thanks!

So technically possible, but useless unless it's cold and sunny aka not the UK generally .

Would like to see some test data.

I had a look there were some tests by people wearing it ( in cold sunny photos) but no data, just the feels.

long wave radiation the outer layer of the coat absorbs will also contribute to the warming of the air

Do long and short waves heat equally? I thought all infra red was in a very short wavelength? Is it the light going through, then getting converted to heat?

I've heard of Maxwell's demon. I tried reading the recent developments on the wiki page and had no idea what it was talking about. The demon is impossible right? The door opening and closing does take energy, so to separate the hot and cold particles and gain energy uses energy and doesn't violate the laws of thermodynamics.

Do long and short waves heat equally? I thought all infra red was in a very short wavelength? Is it the light going through, then getting converted to heat?

Sort of.

All light will turn into heat when absorbed by something, infra-red just so happens to be the wavelength that most things emit (and absorb) at at normal-ish temperatures.  You could heat something up with a green or blue light just the same.  The clever bet would be picking outer layers that were transparent to visible light, but reflective to infra red so they would let energy in but stop it escaping.

Pointless though surely.  In the daytime you're up and about moving and have to regulate your temperature.  It's at night when you're less active that you'd need clever materials.

Theoretically possible - glass lets in solar energy but retains the infra-red that the (cooler!) items behind the glass are emitting.

Polar bear fur similarly, I've heard. It looks white but is actually translucent.

Whether it applies significantly to the item in question, I have my suspicions but haven't looked into it.

Polar bear fur similarly, I’ve heard. It looks white but is actually translucent.

Natures version of fur coat, no knickers then?

So technically possible, but useless unless it’s cold and sunny aka not the UK generally .

Eh. Have you never been to the east coast Scotland?

Sounds like the fabric equivalent of low-E glazing, let’s long wave solar radiation in but then reflects the short wave heat back in to the room (may have got the long/short mixed up there).

Had low-e glass fitted at home and it definitely makes a difference.

Just sounds like old skool East coast Scottish or Geordie skin to me.

Eh. Have you never been to the east coast Scotland?

I'm originally from Edinburgh : ). (Smiley as I see they have stopped working)

I'm always amazed at the level of outdoors clothes people are wearing whole shopping on Princes street. "Just popping to the shops darling" - dones full gortex jacket or a puffa jacket warm enough to walk to the north pole

Carbon dioxide.....it's Carbon Dioxide you need.  That's exactly how it works.