1 Why
Cold kills in hours: know how you lose heat
Wind, wet and the ground steal heat far faster than cold air alone. Every shelter solves the same five problems.
Mild hypothermia
Shivering, cold pale skin, clumsy hands, bad decisions. The "umbles": stumbles, mumbles, fumbles, grumbles. Get them dry, out of wind, insulated, warm sweet drink.
Severe hypothermia
Shivering stops, confusion, drowsiness, slow breathing. Handle gently, keep horizontal, wrap in everything including a vapour barrier (plastic, foil), warm packs on the chest and armpits, not the limbs. See Medical.
Stay dry from the inside
Take layers off before you sweat when working, put them back on as soon as you stop. Cotton is useless wet; wool and synthetics keep some warmth.
2 Tonight
Emergency shelter: small, low, insulated
A shelter only as big as your body. Your body heats the air inside; every extra litre of space is air you cannot keep warm.
Debris hut
Needs no tools and no gear, only a lot of dry leaves or grass. Well built, it keeps a person alive at freezing temperatures without a fire.
Debris hut in four steps
- Prop a strong ridge pole on a stump or in a fork at hip height, the other end on the ground. It must hold your weight.
- Lean sticks (ribs) along both sides, close enough that leaves do not fall through. Inside space: just enough to lie down and turn over.
- Pile leaves, grass, bracken or pine needles over everything, as thick as your arm is long. Lay branches on top to stop wind blowing it away.
- Stuff the inside with dry debris and crawl in feet first. Pull a bundle of leaves or a stuffed bag into the doorway behind you.
When you think you have enough debris, double it. Put your fist through the wall: if you see light, it is too thin.
Tarp and poncho shelters
A-frame
Line tied tight between two trees at waist height, tarp over it, edges pegged low. Sheds rain both sides. Close one end with the tarp corner or your pack.
Lean-to
One edge on a line at chest height, other edge pegged to the ground into the wind. Open side faces a long fire and a reflector wall.
Tarp tent from a sheet of plastic
Builder's plastic, a shower curtain or large bin bags taped together. Small stones wrapped in the corners with cord tied round them work as tie-out points.
Knots worth learning
Bowline (fixed loop), taut-line hitch (adjustable guy line), clove hitch, trucker's hitch for a tight ridgeline.
Any shelter needs a thick layer of insulation underneath: foam mat, spruce boughs, a pile of dry leaves, cardboard, a car seat. A foil blanket helps only if you are wrapped in it and out of the wind.
Snow shelters
Snow is an excellent insulator. Inside a good snow shelter it stays near 0 °C when it is −20 °C outside.
- Quinzhee: pile snow 2 m high and 3 m across, mix layers. Push 30 cm sticks into it all over. Wait 1–2 hours for it to set, then dig in from a low entrance and hollow it until you reach the ends of the sticks. Sleeping platform higher than the entrance, so cold air drains out.
- Tree well: the hollow under a snow-covered spruce, deepened and roofed with boughs.
- Trench: dig a body-sized trench in deep snow, roof with branches or a tarp and snow.
Always poke a ventilation hole the size of a fist through the roof and keep the entrance clear. Keep a digging tool inside. Never burn a stove inside without ventilation; carbon monoxide builds up fast in snow shelters.
A car as shelter
- A car is windproof but loses heat fast through glass and metal. Cover windows with blankets or cardboard, sit on insulation, huddle together.
- Run the engine at most 10 minutes per hour, with a window slightly open and the exhaust pipe checked clear of snow every time. A blocked exhaust fills the car with carbon monoxide.
- Stay with the car in a blizzard; it is easier to find than a person.
3 Where
Choosing a site: look up, look down, look around
Look up
No dead trees or hanging dead branches ("widowmakers") within reach of the shelter. They fall in wind and snow.
Look down
Not in a hollow, stream bed or dry gully: water collects and flash floods come fast. Not on ant nests or animal trails.
Temperature
Cold air sinks at night: valley floors can be 5–10 °C colder than the slope above. Hilltops are windy. Best is part way up a slope, out of the wind.
Wind
On the sheltered (lee) side of a ridge, rock, dense trees or a wall. Door facing away from the wind, towards morning sun if possible.
Resources
Close to firewood and building material. Water nearby, but 50 m or more from it: less cold, damp, insects and flooding.
Be found or hidden
If you want rescue, open ground next to the shelter for signals (see Comms). If you want privacy, keep the fire small and the shelter off trails.
4 Night
Sleeping warm with what you have
You lose most heat into what you lie on. A good mat matters more than a thick sleeping bag.
- Underneath: as thick as the blankets on top. Foam mats, folded blankets, cardboard, sofa cushions, a camp bed off the floor, a straw mattress (a sack stuffed with dry straw or leaves).
- Hot water bottle: a metal or hard plastic bottle filled with hot water (not boiling if plastic), in a sock, between the thighs or on the belly. Warms a bed for hours. Check the lid does not leak.
- Hot stones: heated at the edge of a fire (dry stones only), wrapped in cloth.
- Eat before bed: fat and a warm drink keep the body's furnace going. Pee before sleeping; the body wastes heat keeping a full bladder warm.
- Dry clothes for sleeping only, a hat, dry socks. Put tomorrow's clothes inside the bag so they are warm and dry in the morning.
- Sleep together. Two or three people under shared blankets stay far warmer than each alone.
- Vapour barrier: in deep cold, a plastic bag between socks and boots, or a plastic sheet inside the bedding, stops insulation getting wet from sweat. Change damp base layers.
5 At home
No heating: make one room warm
Heating a whole house on wood or stored fuel is impossible for most people. Everyone lives, cooks and sleeps in one small, well-sealed room.
Pick the room
- Small, with the fewest outside walls and windows. An inner room surrounded by other rooms is ideal.
- Windows facing south (in the northern hemisphere) for daytime sun.
- With a chimney or a window where a stove pipe can safely exit, if you have a wood stove.
- Not over an unheated garage or crawl space, and not in a basement unless it is dry.
Seal it
Free heat sources
Each person gives off about 100 W, as much as a small heater bulb. Cooking, a pot of hot water, the sun through the window and a dog all add up in a sealed room.
Safe indoor heat
A properly installed wood stove with chimney. A battery or solar-powered electric blanket (12 V, 40–60 W) keeps a bed warm for a fraction of what a heater uses. Hot water bottles.
Candle "flowerpot heaters"
A candle gives about 80 W however you arrange the pots. Useful in a tiny sealed space, useless for a room, and a fire risk. Never leave them burning.
Barbecues, charcoal, camping gas stoves for heating, patio heaters, petrol or diesel generators, a car running in an attached garage. They produce carbon monoxide that kills sleeping families every winter. See carbon monoxide.
Damp and condensation
People breathing, cooking and drying clothes in one sealed room put litres of water into the air every day. It condenses on cold windows and walls, bedding turns clammy (and less warm), and mould follows. Open the window wide for 5–10 minutes twice a day ("burst ventilation"): the air changes but walls and furniture stay warm. Dry laundry outdoors or near the stove only, wipe condensation off windows in the morning, keep furniture a hand's width from cold outer walls.
If the house will go below freezing, shut the main water valve and drain the pipes from the lowest tap. Empty toilets and traps or add salt or antifreeze. Burst pipes flood a house when it thaws. See Water.
6 Improve
Insulating a house: the order that pays back
Insulation is fuel you never have to cut. Do the cheap things first.
Draughts
Cheapest and biggest win. Hold a candle or a wet hand near windows, doors, skirting boards and loft hatch on a windy day. Seal with caulk, foam, felt strips, rags.
Loft / roof
Heat rises. 25–30 cm of insulation between and over the ceiling joists. Keep the roof space itself ventilated to stop rot.
Windows and doors
Secondary glazing (plastic sheet on a frame), thick lined curtains, insulated shutters closed at night. A porch or a double curtain at the entrance keeps warm air in.
Floor
Insulate under suspended timber floors from the crawl space, or rugs on top. Seal the gap between floor and wall.
Walls
The most work. Straw bales, stacked firewood or earth banked against a north wall also help.
| Material | Insulation value (λ, W/m·K, lower is better) | Notes |
|---|---|---|
| Mineral wool, glass wool | 0.032–0.040 | Wear mask, gloves, goggles. |
| Polystyrene, PIR foam boards | 0.022–0.038 | Keep away from flames and stove pipes. |
| Sheep's wool, hemp, wood fibre, cellulose | 0.038–0.045 | Natural; wool must be washed and kept from moths. |
| Straw bales | 0.05–0.07 | Very cheap per volume, must stay dry. Rodent-proof with lime plaster. |
| Dry leaves, wood shavings, sawdust | 0.06–0.09 | Emergency filler, settles, fire risk, attract mice. |
| Fresh snow | 0.05–0.15 | Banked against walls in winter. |
| Solid wood | 0.12–0.16 | Timber walls need thickness. |
| Brick, stone, concrete | 0.6–2.0 | Poor insulators, excellent heat storage. |
10 cm of mineral wool insulates as well as about 1.5 m of solid brick. What stops heat is trapped still air. Any fluffy dry material works; wet or compressed insulation almost stops working.
7 Sun
Passive solar: let the winter sun heat the house
Glass facing the sun, heavy material inside to store the heat, and a roof overhang that shades the high summer sun.
Sun height at noon: midwinter = 90° − latitude − 23.4°; midsummer = 90° − latitude + 23.4°. Size the overhang so its shadow covers the window at the summer angle.
Glass
Main windows facing within 30° of south (north in the southern hemisphere). Few and small windows facing north. Keep south windows clean and free of shrubs; plant deciduous trees that lose their leaves in winter.
Mass
Dark stone, tile or brick floor and walls where the sun lands, 10–15 cm thick. Water containers painted dark store even more heat per volume.
Close at night
Windows lose all the gained heat after dark unless covered: insulated shutters, thick curtains, or a panel of foam board pushed into the frame.
Sun space
A glazed porch or greenhouse on the south wall. Open the door to the house on sunny days, close it at night. Grows seedlings too.
Solar air heater
A shallow insulated box on a south wall: black-painted metal (or rows of black cans with the ends cut out) behind a glass or polycarbonate cover. Cool room air enters at the bottom, hot air rises out of the top into the room. A 1 × 2 m panel adds several hundred watts of heat on a sunny winter day, nothing when cloudy. A flap on the inlet stops it running backwards and cooling the room at night. A small 12 V fan from a PC helps (see solar power).