I slept at –18 °C (0 °F) in Colorado’s San Juans with 800 g of sleep gear. No bag, no pad, no regrets. Here’s the exact kit and protocol.
The 800 g Kit
- SOL Escape Lite Bivvy – 155 g (breathable, not waterproof).
- Borah Gear polycryo ground sheet – 60 g.
- Montbell plasma 1000 puffy (hooded) – 310 g.
- Possum-down beanie + buff – 75 g.
- 750 ml Ti bottle + foam cozy – 200 g (hot bottle).
Site & Shelter (15 Minutes)
- Pick a site 2 m below ridgeline—cold air sinks.
- Dig a 20 cm hip/shoulder trench in snow; pack walls 40 cm high.
- Roof with a 2 × 3 m tarp pitched 50 cm above—reflects radiant heat.
Pre-Bed Routine
- Eat 600 kcal fat bomb (salami + cheese).
- Boil 750 ml water 20 minutes before lights-out.
- Strip damp layers; store in pack foot.
- Don fresh merino base if carried (100 g extra).
Sleep Stack
- Polycryo on snow.
- Puffy worn, hood cinched to 8 cm opening.
- Bottle at groin—rotate every 90 min.
- Arms inside puffy; knees drawn up.
Heat Budget
- Body idle: 60 W.
- Losses at –18 °C: 110 W.
- Bivvy cuts 40 W, puffy traps 35 W, bottle adds 30 W for 3 h, snow walls + tarp reflect 15 W. Net: +20 W = toasty.
Field Data
- Night temp: –18 °C.
- Bivvy foot frost: light, shook off at 0600.
- Core temp on wake: 36.4 °C.
- One Esbit tablet boiled the bottle.
Fail-Safes
- Shivering starts? Do 20 jumping jacks inside bivvy.
- Bottle cools? Refill from snow melted in a pot over body heat.
Scale It Down
- Swap plasma puffy for 650-fill (add 80 g, lose 2 °C rating). Still under 1 kg.
This 800 g system turns brutal nights into bragging rights. Pack it, test it above 0 °C first, then push the envelope.
Tell me in the comments: What’s the lightest sleep setup you’ve survived?