Gear Reviews
Emergency Bivvy Sacks: Cheap Insurance Against Hypothermia
An emergency bivvy weighs 3-5 ounces and can save your life. These simple reflective sacks trap up to 90% of your body heat, turning a dangerous exposure situation into a survivable one.
How They Work
Emergency bivvies are made from heat-reflective material (similar to space blankets but in sack form). You crawl inside like a sleeping bag. Your body heat reflects back instead of radiating away. The sealed design also blocks wind and rain.
Bivvy vs Emergency Blanket
Emergency blankets are flat sheets — they blow around, tear in wind, and require effort to wrap around yourself. Bivvies are enclosed — crawl in, done. In a real emergency when you’re cold, exhausted, and possibly injured, simplicity wins.
When to Use
- Unexpected overnight — Lost, injured, or caught by weather
- Waiting for rescue — Maintaining body temperature while help arrives
- Backup sleep system — If your sleeping bag gets wet or fails
- Emergency first aid — Treating shock victims who need warmth
- Minimalist camping — Some ultralight hikers use bivvies as their primary shelter in warm weather
Limitations
- Condensation builds inside — you’ll get damp over long periods
- Not a replacement for a real sleeping bag in cold conditions
- Single-use cheaper models tear easily. Reusable models are slightly heavier but far more durable
- No insulation from below — you still need ground insulation
What to Look For
- Reusable construction (slightly thicker material)
- Sealed seams (prevents wind and rain entry)
- Bright color exterior (orange or green for visibility/rescue)
- Large enough for your body plus some gear
Where to Carry One
Every outdoor pack, vehicle emergency kit, bug out bag, and even office desk drawer. At the size of a fist and weight of a few ounces, there’s no excuse not to carry one whenever you’re outdoors.
