How and Why to Set About Building an Igloo, For Beginners.
For starters igloos are rather nice things to construct when one is stuck in the middle of nowhere and you have an ample supply of snow and little else. In my experience a single candle can heat a moderate sized igloo, (about the same size as a two to three person dome tent,) to the point where you are going to want to climb out of your sleeping bag in the middle of the night. They have the additional advantage of being completely disposable and are non-environmentally impacting in the event that you decide to abandon one. If done with care an igloo can also be expanded beyond its original size. (See below.)
How to build:
-Flat piece of sheet metal, approx. 24-36 in. square.
(Note: In the event of a situation where you decide to do this and have no metal. Ski's, the end of a snowboard, a large sheet of cardboard, and any other flat, square material can be used. Don't be afraid to experiment.)
-Some creativity and an ability to stick to a plan.
1. Find a suitable spot, preferably flat and in the open. (If for extended use, avoid trees as snow falling from branches can easily crush an igloo, no matter how well built.)
2. Stamp out or excavate a large circular shape until you have a suitable foundation to build on. The more stable, the better obviously. I would encourage those living in their eventual construction to minimize excavation as it saps strength and instead concentrate on walking around in circles until such a point as which you are no longer sinking into the snow when you take a step. Leaving small footprints is fine, concrete isn't necessary.
3. Nearby to your building site locate another flat area of packed snow, or create one. Depth of the packed snow must be at least two to three feet, ideally. Excavate a small trough around the area so that you have access to the bottom of the packed area. In a perfect situation you have packed probably close to three or four feet of snow in a ten to fifteen foot square area. This creates a 'quarry' of sorts from which your igloo will be built.
4. Take sheet metal, (.030mm to .050mm in width,) hard cardboard or whatever is at hand and push down vertically to create a square shape in the quarry, on one corner. Slide metal underneath and then pick your block up like a pizza out of an oven. Lay this down at the building site and repeat until you have a ring equal to the internal diameter of the igloo you want to build. Make sure that blocks meet and seal nicely together at the inside bases. (Note: It is not necessary or needed to create a perfectly circular igloo as seen on TV and other sources. The outside of your igloo can undergo aesthetic changes later, concentrate on construction for now.) On the other hand do not go and build a ziggurat, pyramid or large cube shaped thing, the dome is the most stable and easiest to build, stick with the circle. (Ellipses are okay as well for beginners, just try to avoid that situation, as the end product will be less stable than a circular dome.) One of the critical factors here is that the snow you are using MUST be well compacted, as this ring will shortly become a load bearing member. Additional settling will cause the igloo to collapse if care is not exercised.
5. Place more blocks slightly on top of and slightly to the inside of the first ring. Take spare packed snow created by the block process and pack it into the cracks between the first and second levels of blocks, and any fissures between blocks. Repeat this process until you have a nice dome. Ideally one person should remain inside the igloo and one outside to assist in the placement of blocks during construction. Additionally do not attempt to build a door into your igloo at this point.
. Circular in shape, or you can simply place a cone shaped block into the hole at the top of the igloo. Care should be taken during the construction process to ensure that the person on the outside of the dome can reach the top center upon completion. Hand this to the person on the inside of the igloo, (or put in place yourself if building alone,) and shave to fit.
7. Door/Ventilation. (This point is where the majority of igloos will collapse, so be careful doing this.) Tunnel until you have an opening just larger than yourself through the wall and into the igloo. Construct out of smaller blocks or snowballs an arcing entryway that extends two to three feet from the side of the igloo. Just outside the door, (with enough space to move freely,) build a large wall curving around on the ground in front of the door. (This is a windbreak.) The door should be as close to, if not slightly below level of the base of the igloo. Keep in mind not to dip below the outside of the wall, as you will create a pocket that will prevent carbon dioxide from escaping. Once the door is complete, crawl inside cut a small hole about the size of your arm about three quarters of the way up the leeward side of the wall. Do not cut at the exact top otherwise you'll wind up wasting all of the heat. The vent hole is there simply to allow some air to circulate, and to avoid carbon dioxide poisoning while sleeping. Sit inside your igloo for about a half-hour, if you begin to have trouble breathing or it begins to become stuffy, LEAVE IMMEDIATELY. Give the atmosphere inside the igloo time to change out and add additional venting as necessary.
8. Insulation. (Not particularly necessary, but nice nonetheless.) Find a green deadfall and begin removing branches from the tree. The greener the better. If possible locate a large amount of dry to semi-dry fallen pine needles. Liberally scatter these about the floor of the igloo until you have a three to four inch bed at the bottom. You should be able to see six to eight inches of daylight on the windbreak outside the door at this point. The idea of the insulation is to keep yourself off of the snow, thereby avoiding the waste of body heat required to keep you warm at night. EXTREME CARE should be taken with fire inside the insulated igloo.
9. Heating. (Advanced.) Igloos, once ideal ventilation has been figured out, can be heated with a single candle for a number of hours. Radiated heat from the candle and from people inside the structure will actually cause the inside walls to melt just a little and then freeze, causing the formation of a layer of ice on the inside of the igloo. This is a VERY good thing since in this particular case the ice provides a wonderful and very efficient source of insulation. Air gaps are completely sealed, (with the exception of the vent,) heat is actually reflected off of the ice and back into the igloo. Keep an eye out for structural degradation in igloos with thin walls or structures that have been inhabited for extended periods of time.
10. Smug sense of self-satisfaction. Stand back and admire your work, keeping in mind that at some point it is going to go all melty. That I believe, is the impermanence of all things, Buddhism, and another node entirely.
WARNING: IF you find yourself in a situation where shelter is a matter of life and death, DO NOT ATTEMPT CONSTRUCTION OF AN IGLOO. Burrowing into ANY convenient snow bank and creating a hollow spot inside big enough for you and anyone else you might be with is the MOST PRACTICAL option in this situation. The PRIME KILLERS in winter survival situations are DEHYDRATION and EXHAUSTION. Large amounts of arduous manual labor WILL DEHYDRATE and WILL EXHAUST you and you WILL DIE. If this is the last thing you read before you go out for a trip with Donner Winter Excursions Ltd., take with you three things that having been lost in the middle of nowhere I found somewhat useful:
1. DO NOT PANIC. DO NOT GIVE UP.
2. STAY WHERE YOU ARE.
3. BURROW LIKE A BUNNY.
If the remotest possible chance exists of a situation arising where you may be in need of shelter on an emergency basis, I would suggest taking a winter survival course through the Red Cross, YMCA, Community College or whoever it might be where you're living that offers this sort of education.
The source material that has been provided along with the plans and advice above are from numerous Winter Survival Preparedness sessions I attended in my eleven years as a Boy Scout. Also I have included experience gained over several dozen trips into the, Sierra Nevada, Jemez and Sangre de Cristo mountains during winter, and what little I know of structural engineering.