The kind of structure you build depends a lot on the snow conditions where you are building it. I don't spend a lot of time where the snow is stiff enough to make an igloo (unless I use an igloo tool, which is fun as a novelty but not something I want to drag around on a backpacking trip). Instead I like to make a structure from the softer, denser snow of the sierras, using a technique closer to carving out a cave.<p>Making a structure at all depends a lot on your plans. It takes time, but is worth it if you're going to spend a couple of days in one place, especially if there's a storm coming in (that you were foolish enough not to plan for, <i>cough</i>). If you're traveling, it's often easier to simply sleep out in the open (I dig a shallow trench about 500 mm deep to avoid convection cooling overnight). This probably sounds crazy but once you do it you'll find you sleep fine. I learned it on a camping trip in Minnesota where the overnight temps were below 0 Fahrenheit. I was quite dubious at first but my friends insisted it would be fine and they were right!<p>If you look at the Nanook of the North video, you'll see they make pretty solid and large igloos and then move into them for extended periods. In that case it's worth the time it takes to get the job done really well.<p>I teach my students to make emergency shelters in ways that are quick and temporary, using whatever is at hand (branches, skis, random tree wells, etc). If it's an emergency, you presumably don't have the time to making anything fancy. (I only once ever heard of a former student actually doing this).<p>Sadly, climate change has made the snow conditions in most of the sierras unsuitable for making shelters for the past few seasons.