Snow Shelters
Part of Emergency Shelter
Snow is one of the best insulating materials available in winter — a properly built snow shelter maintains interior temperatures near 0 degrees C even when outside air drops to -40.
Why Snow Works as Insulation
Fresh snow is roughly 90% trapped air. Air is a poor conductor of heat, so a wall of packed snow acts like a thick blanket between you and the killing cold outside. This is the same dead-air principle behind every shelter, but snow provides it in abundance with no tools required.
| Property | Value |
|---|---|
| Thermal conductivity of snow | 0.05-0.25 W/m-K (depending on density) |
| Thermal conductivity of still air | 0.025 W/m-K |
| Thermal conductivity of solid ice | 2.2 W/m-K |
| Interior temperature of snow shelter | -2 to 0 degrees C |
| Minimum wall thickness | 30 cm (12 inches) |
The key distinction: packed snow insulates. Solid ice does not. If your walls melt and refreeze into ice, you lose insulation and gain a cold, dripping ceiling. This is why you never use open flames inside snow shelters.
Types of Snow Shelters
Choose your shelter type based on snow conditions and available time:
| Shelter Type | Snow Needed | Build Time | Best For | Skill Level |
|---|---|---|---|---|
| Quinzhee | Any snow, 60 cm+ depth | 3-4 hours (includes settling) | Most conditions, any snow type | Beginner |
| Igloo | Wind-packed or dense slab snow | 2-3 hours | Arctic conditions, firm snow | Advanced |
| Tree well shelter | Deep snow around evergreens | 30-60 minutes | Emergency, heavy snowfall areas | Beginner |
| Snow trench | Firm snow, 1 m+ depth | 1-2 hours | Quick overnight, firm snowpack | Beginner |
For most post-collapse situations, the quinzhee is your best option. It works with any type of snow — wet, dry, powdery, or dense — and requires no special skills or tools beyond a digging implement.
Universal Snow Shelter Principles
Regardless of which type you build, these rules apply to every snow shelter:
1. Entrance Below Sleeping Platform
Cold air is denser than warm air. It sinks. Your entrance tunnel must be lower than your sleeping area so cold air drains out and warm air from your body stays trapped at ceiling level. A difference of even 30 cm (12 inches) between entrance floor and sleeping platform makes a measurable difference in temperature.
2. Dome the Ceiling
A domed or arched ceiling forces meltwater to run down the walls instead of dripping onto you. Flat ceilings collect droplets that fall directly on your body and gear. Smooth the ceiling with your gloved hand after hollowing — remove any bumps or flat spots where water can pool.
3. Ventilation Is Non-Negotiable
Carbon dioxide and carbon monoxide kill silently
A sealed snow shelter traps exhaled CO2 at dangerous levels within hours. Always maintain at least one ventilation hole (fist-sized minimum) in the ceiling or upper wall. Check it periodically — drifting snow or frost can block it while you sleep.
Poke a ventilation hole with a stick or ski pole at a 45-degree angle through the ceiling. If you notice headaches, drowsiness, or shortness of breath, your ventilation is inadequate. Open the entrance wider immediately and punch additional holes.
4. Wall Thickness
Maintain minimum 30 cm (12 inches) wall thickness everywhere. Thinner walls lose structural integrity and insulation value. During construction, insert sticks of known length (30 cm) into the mound from outside — when you hit the sticks while hollowing, stop digging in that direction.
5. Mark Your Shelter
Snow shelters are nearly invisible from outside, especially during snowfall. Mark yours with an upright stick, brightly colored cloth, or pile of dark objects on top. This prevents others from walking on it (collapse risk) and helps you find it if you leave to gather firewood.
The Snow Trench — Fastest Option
When time is critical and snow is firm enough to cut blocks, a snow trench can be built in under an hour:
Step 1 — Dig a trench 60-75 cm wide (shoulder width), 90 cm deep, and long enough to lie in (about 2.5 meters). Pile excavated snow along both sides.
Step 2 — Cut snow blocks or lean branches, skis, or poles across the top of the trench. Cover these with a tarp, emergency blanket, or more snow blocks.
Step 3 — Insulate the floor with pine boughs, a sleeping pad, or packed snow covered with any fabric you have. The ground beneath the snow is often warmer than the air but still conducts heat away from your body.
Step 4 — Block one end completely. Leave the other end as your entrance, partially blocked with a pack or snow block.
A snow trench is not as warm as a quinzhee or igloo, but it gets you out of wind and provides meaningful insulation in under an hour.
Tree Well Shelter
In forested areas with deep snow, large evergreen trees create natural wells — the branches shed snow outward, leaving a depression around the trunk. These are ready-made emergency shelters:
Step 1 — Find a large spruce or fir with low-hanging branches and a visible well around the trunk. The well should be at least waist-deep.
Step 2 — Carefully climb or slide into the well. Do not break the branches above — they are your roof.
Step 3 — Dig out the well floor to create more headroom. Pack the walls. Add boughs from nearby dead trees to the floor for insulation.
Step 4 — Pull lower branches down and anchor them with snow to close gaps.
Tree well suffocation hazard
Loose, deep snow around trees can collapse inward. If the snow is powdery and unconsolidated, do not use a tree well — you risk being buried in loose snow with no way to dig out. Tree wells work best in consolidated snowpack.
Staying Dry Inside
Moisture is the enemy inside any snow shelter. Your body produces roughly 1 liter of water vapor per night through breathing and perspiration. This moisture condenses on cold walls, drips, and soaks your clothing and gear.
Countermeasures:
- Smooth the ceiling so water runs down walls, not onto you
- Sleep on insulation, not bare snow — pine boughs, a foam pad, a pack, anything
- Remove wet outer layers before entering — brush off all snow at the entrance
- Keep the entrance partially open for air circulation, even if it costs a degree or two of warmth
- Do not cook inside unless the shelter is large with excellent ventilation
Key Takeaways
- Snow shelters maintain interior temperatures near 0 degrees C regardless of outside conditions because packed snow is 90% trapped air.
- The entrance must always be lower than the sleeping platform — cold air sinks and drains out.
- Ventilation holes are mandatory — CO2 buildup in sealed snow shelters can kill you in your sleep.
- The quinzhee works with any snow type and requires no special skills — it is the best general-purpose snow shelter.
- Staying dry matters as much as staying warm — manage moisture aggressively inside any snow shelter.