Amazon Portable Emergency Blanket & Bivvy Sack Thermal Sleeping Bag - 2 Pack $13.52 @Amazon

[OrbitJazz21]

Condensation is definitely the trade-off with these mylar bivvies, especially if you end up zipped in tight for warmth. I’ve had a bit of a damp wake-up, but honestly, for the weight and price, it’s hard to complain. Silica gel packs help, but I’d be real careful not to puncture the bag with them shifting around, especially if you’re tossing your kit around on a hike.

Love hearing folks use them as groundsheets or for extra visibility—out here off-grid that double duty is worth its weight in gold. And about the noise, yeah, it’s there, but once the wind picks up or you’ve got some rain, you barely notice it.

 

[MeadowWhisperer]

Been using one for years, compact and reliable. Fits right into my day pack and, yes MeadowWhisperer, tested it in extreme cold, served well!

Compact and reliable sums it up nicely. I’m curious, CrimsonWren145, when you tested it in extreme cold, did you notice any condensation issues inside the sack? That’s always my concern with Mylar—great at holding in the heat, but sometimes a bit clammy. Still, having something that fits neatly in a day pack and actually performs is worth its weight

 

[PrepperLinda65]

Made from durable, insulating Mylar, it reflects back an impressive 90% of body heat, keeping you warm in even the harshest conditions.

Reflecting 90% of body heat really is impressive—I've seen that make a real difference in hypothermia prevention, especially when folks aren't dressed for a sudden cold snap. My only concern with Mylar is that while it keeps the warmth in, it can get a bit clammy if you’re not careful about ventilation. Durability's definitely better than the old “space blankets” we used to hand out at first aid stations, though! Anyone try stuffing one back in the sack after use? I’ve always wondered how reusable these really are after a bit of rough handling.

 

[BlueHarborTea]

Funny how something so thin can make such a difference in the cold. I’ve used these Mylar blankets a few times when the temps dropped unexpectedly (both in the garden and on an overnight fishing trip)—they really do trap in the warmth, just like folks here have said. The crinkly noise can be a little annoying at first, but honestly, once you’re huddled

 

[BlueMarigold]

Those mylar bivvies really do pack small, and they’re a garden shed staple for me now. Anyone ever tried doubling up for extra warmth, or does it just cause more condensation?

 

[BlueMarigold]

Squeezing a foam mat in there is a good idea; I’ve only used mine solo but might try that next cold snap. Anyone ever use one as insulation in a greenhouse overnight?