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Snow Shelter - Snow Cave





Basic shelter building is a skill that every person should consider learning. To the outdoor sport enthusiast, emergency shelter building knowledge is critical. Proficiency in shelter building could make the difference between life or death in an emergency. Wilderness shelter building is fun and can make a lightweight backpacking trip more comfortable. Whether you choose to use man made items such as a tarpaulin or natural resources, we should make it a point to become familiar with different types of survival shelters. Countless articles of lost backpackers reach the media yearly. Regardless of how many people get lost in the wilderness, the common mentality is ‘it will never happen to me’. Skiers, hunters, backpackers can often find themselves disoriented in the frozen woods in a possibly dangerous situation. Poor planning can often be the cause but no matter how much planning we do, sometimes things just do not go as planned.

In this article we will discuss one of the common cold weather shelters the snow cave. Winter snow shelters is a complex subject which cannot be covered in an article. There are complete books written on this subject. Our intent is to merely discuss our experience with building such a shelter. There are several snow cave / quinzhee hut designs. It is a good idea to take the time to build different shelters in a non-emergency scenario. This allows us to learn from our mistakes in a relaxed environment and gives us confidence in our knowledge if an emergency situation emerges.

So what challenges do we face ? The normal human body temperature is around 37.0 °C (98.6 °F). In a winter cold weather environment hypothermia is our enemy. If we allow the body core temperature to drop a few degrees below our normal human body temperature, we will begin to see symptoms of hypothermia. A cold weather shelter should protect us from precipitation and wind. A good night of rest is essential especially during a stressful ordeal.

Having some basic knowledge of how the human body will lose heat (heat transfer), should help us to dress properly and build more efficient shelters. Heat flows from hot to cold. If the temperature of the air outside is colder than 37.0 °C (98.6 °F), we have to use proper clothing and shelter to protect our body.


Ways to lose heat:

Convection

The dictionary defines convection as the transfer of heat by the circulation or movement of the heated parts of a liquid (rain) or gas (wind). For our situation, we would be dealing with cold air movement over our clothes, and body. We will want to minimize cold air flow, without over heating and sweating.

Conduction

The transfer of heat between two parts of a stationary system, caused by a temperature difference between the parts. In other words the transfer of heat by direct contact to a colder surface. Laying your body against a cold surface will quickly transfer the heat from your body parts to that surface. We want to insulate our body from the ground within the shelter floor.

Radiation

a. the process in which energy is emitted as particles or waves.
b. the complete process in which energy is emitted by one body, transmitted through an intervening medium or space, and absorbed by another body
c. the energy transferred by these processes.

The dark night sky will take heat from our body as it cools down the earth.

Evaporation

We have to remember heat loss through breathing and the negative effects caused by the moisture our body exhales.

A properly built snow shelter should immediately block a lot of the wind. If the wind chill factor is around -17.7 °C (0 °F), the inside of a snow shelter can be kept around 0 °C (32 °F). By simply getting out of the wind we can have a temperature difference of thirty two degrees Fahrenheit. Imagine all the difference that could make. The snow shelter could also protect us from freezing rain. Allowing your clothes to get wet would lower the insulation value or Clo. Its important to remember this since we will be crawling in and out of a snow shelter. Properly insulating the shelter floor will help avoid heat loss by conduction and possible humidity getting on our clothes.

Note:

It is important to try this type of shelter in different conditions. The snow will not always be optimal for this type of shelter. Sometimes moving the snow and allowing it to settle will help. For this reason it is important that we learn different types of shelter and fire types.

If the snow conditions are not optimal for a snow shelter, an option is to build a long parallel fire with a reflector. Hopefully we can build one on our next winter trip. In the meantime, here is a fine example from our friends at Wilderness Essentials Survival Windbreak/Reflector Log Shelter with fire and firewall


Wilderness Essentials Survival - Chris Caine



In the end there is no replacement for being well prepared. Take the time to read books from authors such as Mors Kochanski on winter survival and the super shelter. My friend Caleb Musgrave with http://www.canadianbushcraft.ca/ teaches bushcraft in the Ontario area. The book snow caves by Ernest Wilkinson is a good source of information as well.

Note:

There are a lot of people that will talk about going into the wilderness with "minimal" gear. The idea to push every person to go into winter wilderness with minimal gear is ignorant and dangerous. Each person is at a different stage of learning and some have perished listening to armchair bushcrafter/survivalist. The Native Americans stored food for the winter, prepared their pelts in the summer, all while working as a team. Use whatever tool and equipment needed to keep you alive as you learn. Same with primitive skills, we practice fire by friction, but we carry a Ferrocerium rod and Trioxane bars. If there are people that have the option to live in the bush for months at a time, that is great. But most of us, have a family, a job and we have limited time in the bush. So travel safely and do not let others push you into a dangerous situation.


With these things in mind, we set off to build a basic snow cave. If sufficient snow is not available to build a snow shelter, a DEBRIS SHELTER would be one alternate solution.




Perhaps you do not have sufficient materials or are in a hurry. We could try using a fallen tree or rock formation to help block the wind or build a snow trench to get us out of the wind. A snow trench can be covered using a reflective tarp or pine branches if available.

Here is a snow grave shelter built my Matthew Lodge of Wilderness Essentials during Artic Survival training.

The Field Manual for the U.S. Antartic Program has examples of different snow shelters.


First step for shelter building is finding the proper location. Proper location of the shelter can make a huge difference in temperature and safety. Avoid building your shelter under a tree with large dead branches (widow makers). Avoid building near a body of water. The water levels could change without warning. Try to protect yourself from the wind and find the “sunny” side if possible.

We found an area where the wind created a snow drift. This should shorten our shelter building time. We began by walking on top of the snow with our snow shoes and making a general outline of the shelter floor.





It is a good idea to carry a shovel but if one is not available, we can use a snowshoe, ski, drinking cup or the plastic liner from the inside of some backpacks.





For this shelter we shovel snow to a height of about around 5 foot tall and 9 foot long. If planning on building a cold well and raised bed, the shelter would need to be larger.


Note: My good friend Caleb Musgrave from Canadian Bushcraft explained to me that in this same shelter, I could have dug out a small trench (no boughs) next to me or at least near my head to help collect some of the colder air. Make sure to take a look at his site and you tube videos.


http://www.canadianbushcraft.ca/





After building the pile of snow, we allowed the snow to bond and settle. This usually helps the snow stay together as we hollow out the cave. This time can be used to gather insulation. Spruce / Pine boughs work well for insulation.




Placing the spruce boughs with the stem or butt side down seems to help with comfort and trapping of air. Remember we want to reduce heat loss by conduction and convection. The spruce bough 'mattress' should be several inches thick after being compacted down by laying down on it.

We let several hours pass and we begin to dig out the cave. It is important to wear waterproof clothing if available. Laying down while digging and snow dropping from the roof of the cave can dampen clothing which is dangerous in a cold weather conditions. Wet clothing can loose more than 80% of its insulation value.






As we continue to dig further into the cave, we lay down a base layer of pine boughs to help keep our body from being in contact with the cold snow.




Carefully we carve the ceiling on the cave in a smooth dome shape. The dome shape will allow more freedom of movement and should add structural integrity. If for any reason the inside of the shelter walls were to melt, we want to avoid dripping on our sleeping area. Unless you are planning on having a small fire inside the shelter, a ventilation hole is usually not needed. Unless the snow is melted with a heat source and the frozen snows freezes, the snow should allow some ventilation.

Wall thickness recommendations are usually 12+ inches. Some people prefer to use small twigs cut to the desired length. The sticks are pushed into the outside shell of the snow shelter. The purpose is to know when to stop digging out the wall while hollowing out the snow cave.

We crawl into the shelter and make sure the cave is deep enough so our feet will not be near the door. Your body temperature will drop in the later part of the night while sleeping. Something to keep in mind. According to the Circadian rhythm information we read, the average human temperature is usually at its lowest point in the early hours of the morning. We want to make sure to avoid frostbite on the extremities.





If we were planning on a longer stay, a quinzee / quinzhee hut would be a better shelter. Adding a raised bed and a cold well will make the sleeping area warmer. The hot air raises, and the cold well allows the shelter to have an area where the colder can drop. We carried several emergency candles for light and a little bit of added warmth within the shelter. A snow trench is another cold weather snow emergency shelter option. We will cover the snow trench and quinzee in separate shelter articles.

Once the interior of the shelter is finished, we lay out the pine boughs. For this shelter spruce boughs were used. We tried to use only the lower branches for this practice shelter in hopes of causing less damage to the trees. We crawl in several times, compressing the insulation down and adding more layers.






A thick mattress of pine boughs will help ensure a more comfortable and warmer night while sleeping. So here is our finished product.





We spent the night in the shelter. Later that night around midnight, we had a curious visitor stop by the cave.




Door

Your backpack can be used to block the wind on the door of the cave. Another option is to build a snow plug for a door. Roll a snow ball, or use a piece of cloth. Lay the snow on the cloth and shape it. After a few hours the snow for the plug will harden.

Note: We always carry the shovel into the shelter in case of a hard snow during the night.



Backpacking and other winter activities can be fun and rewarding. Learning bushcraft / survival skills can be fun and should an emergency arise, can help us have the confidence we need to get through a difficult situation.





Lower human traffic usually means better opportunities to see wildlife. Beautiful scenery awaits you in the winter paradise. Plan ahead, let someone know your plans and location. Finally some basic knowledge of cold weather survival skills can help ensure we get home safe. Take the time to learn these valuable Bushcraft skills and enjoy yourself while doing it.






Great article on Sheltercraft by my great friend Caleb Musgave of Canadian Bushcraft
Sheltercraft











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