Extreme green

Let it snow
As a skier and someone concerned about California’s drought, I’ve been pleased with the recent accumulating snowpack. If you haven’t noticed, six to eight feet of new snow have fallen in the higher elevations around Mount Shasta, Lassen Park and the Sierras during the past two weeks. PG&E’s snow sensor at 8,250 feet in Lassen Park now indicates about 11 feet on the ground. With this in mind, I thought I’d talk about one of the most sustainable shelters for surviving winter in the mountains.

Log cabins, yurts and tents all qualify as viable mountain abodes, but the most sustainable would have to be an igloo or snow cave. Employing renewable, natural materials—and totally recyclable—snow shelters have virtually no environmental impact or carbon footprint.

If you’re thinking that snow shelters are cold and uncomfortable, remember that comfort is relative. You certainly won’t be able to strip down to a T-shirt and shorts; however, you will be much warmer than in a tent or unheated yurt. Eskimos used snow shelters for centuries, so they can’t be that uncomfortable!

Surprise!
I often assign a snow igloo homework problem in my “Heat Transfer” class. I give students the hemispherical dimensions, snow properties, outside temperature, wind speed and the heat-generation rate of four occupants. Usually, students are surprised when they calculate that the inside air temperature is nearly 40 degrees when the outside temperature is 10 degrees below zero with 50 mph wind!

This large temperature difference is due to the R-value of snow. Because snow contains minute air pockets, its insulating value is enhanced well above that of ice. The R-value depends upon snow density, so snow packed into igloo blocks will not be as insulating as freshly fallen snow. Even so, the R-value of 8-inch-thick snow blocks is about R-5. Shoveling fresh snow over the entire shell can further increase the R-value.

Team work
Snow caves are pretty easy to build but they require a lot of shovel work and sufficiently deep snow on a slope. Igloos take more technical know-how (and a saw) but can be built on flat ground with less snowpack. I’ve found that an igloo for four people will take several hours to build with everyone helping.

Igloo ABCs
A snow igloo is really the perfect barrier against the elements in a hostile winter storm. On Alaska’s Mount McKinley, I’ve experienced their wonderful attributes in conditions where even the best expedition tent wouldn’t survive the extreme winds. The sound-dampening properties of snow are amazing—a howling storm is totally silenced by a 6-inch wall.

There are a few important dos and don’ts with igloos. Don’t cut the blocks too big because you must lift them. Be sure to add a ventilation hole in the shell and keep it clear during storms. Also, keep cooking to a minimum, since the temperature will rise and may start to melt the inner wall, causing some nagging dripping and wet sleeping bags.

Building and sleeping in an igloo is the quintessential snow camping experience. Sustainable, affordable and (relatively) comfortable!