Emergency warm layer

D&D and I have both made something similar out of bubble wrap, except that doesn’t store compactly.  And no aluminized surfaces.

Since it has zero breathability, you could get condensation inside.  If you were cold and in emergency mode maybe condensation would be minimal

Too bad it’s not one row longer

It’s an interesting idea — the wearable version of a thermal sleep pad. This has been discussed before, although I don’t recall any notable conclusions. PFDs are similar, but tend to be heavy. To be of value for emergencies it must compete with down in warmth:weight, with bonus points for waterproofness and coverage. Two ounces would be competitive.

The XeroVest is one size (small). Might work to some extent as long as you can get your arms through the sleeve holes. $14 on their web site.

Dave Thomas told an interesting story about using crumpled newspaper to stuff whatever shirt or jacket you have with you. Nice!

Of course, newspapers are heavy, but what about stuffing your shirt/jacket with a pair of those UL pillows from AntiGravityGear or LiteSmith? They weigh 27 g (1 oz) each, and should pack small. Wrapping with a space blanket might help a little, for only a few grams. (Plus they double as pillows.)

or stuff leaves inside your jacket

@Steve and @Jerry, I had never seen that Xero vest, thank you! For that price and weight, I’ll give it a shot. Also, it would act as some cushioning for someone lying down, wether to sleep in an emergency bivouac, or for a sick/injured patient.

I don’t see the utility of stuffing anything but air inside. Leaves tend to be wet. Not to mention, mostly  in the winter they are not around.
‘newspapers work great for road bikers on a big descent, because they block wind, but again, rarely available in the backcountry.

Yeah, wet leaves wouldn’t be so good

do you think a Das Light Hoody offers the most warmth : weight ratio?

No. That would be down. For synthetic, the Das light works very well. I can layer underneath it very easily. I’ve used a down vest under it without compressing the down. Wind resistant, water resistant. I have a bunch of rips in mine, but from daily use. I don’t baby it. You can find them with big discounts. Layered up underneath, it’s good down to about 10*f. I’m not really cold in it at 0*f, if I’m dressed right. Especially with a vest.
I didn’t know what a Blizzard jacket was. I Googled it and was getting hits for big heavy parkas.
The XeroVest looks more in order. I think I’d buy one and try it before depending on it. Talk to search and rescue and get their advice.