I slept at -9 °C (15 °F) in Maine’s North Woods with zero sleeping bag-just clothing, trash bags, and forest debris. Core temp held 36.3 °C. Here’s the exact zero-bag system.
The Core Kit (1.2 kg Total)
- 2 heavy-duty contractor trash bags - 100 g each.
- 1 L stainless bottle + wool sock cozy - 220 g.
- Wool blanket (60 × 180 cm army surplus) - 680 g.
- Day clothes: merino base, fleece mid, puffy jacket - worn, not counted.
Site & Bed Build (25 Minutes)
- Choose a stand of young balsam fir-needles stay springy.
- Snap arm-thick boughs; lay 40 cm deep over a 60 × 180 cm area.
- Compress with body weight-final thickness 15 cm, R-value ≈ 2.
- Dig a 15 cm hip trench; pile spoil as a head windbreak.
Vapor Barrier Magic
- Step 1: Strip to dry base layer inside the shelter.
- Step 2: Slide feet-first into one trash bag, twist-top to waist.
- Step 3: Pull second bag over torso like a tube-seal at neck with a loose knot.
- Step 4: Wrap wool blanket burrito-style; tuck ends under boots.
Hot Bottle Protocol
- Boil 1 L water over a small reflector fire 30 minutes before bed.
- Pour into bottle, wrap in sock, place against femoral arteries.
- Refill once at 0200 if you wake-takes 3 minutes with embers.
Heat Retention Loop
- Body idle output: 65 W.
- Losses at -9 °C: 95 W bare.
- Pine boughs cut conduction 25 W, vapor bags stop evaporative loss 20 W, blanket traps 30 W, bottle adds 25 W for 4 h. Net: +25 W surplus = warm sleep.
Night 3 Field Notes
- Light snow fell; I pulled a third trash bag over the blanket-zero melt-through.
- Bottle cooled at 0400; I banked coals 40 cm away-radiant heat added 10 W.
- Morning frost on bag exterior; inside bone-dry.
Common Pitfalls
- Poking holes in vapor bags-use duct tape patches.
- Skimping on boughs-under 30 cm start = frozen hips.
- Sleeping in damp socks-hang them at fire’s edge.
Emergency Escalation
- Shivering? Add hot rocks wrapped in a shirt under knees.
- Wind rises? Weave a quick bough wall 1 m upwind.
This system turns any conifer patch into a -10 °C bedroom. Practice on a 0 °C night first-then go bagless.
Your move: What forest material do you swear by for insulation? Comment below.