Dr. Norbert E. Yankielun is a research engineer for the U.S. Army Corps of Engineers, Cold Regions Laboratory, which basically makes it sound like the guy should have his own G.I. Joe character action figure with a code-name like "Iceman."

Yankielun's specialty is Cold Climate Radar Systems but his passion is making igloos and snow shelters, and he's happy to share his knowledge; the good doctor runs open-to-the-public igloo-building workshops when he's not making sure those green blips still show up at -20 degrees.

Check out his book How to Build an Igloo: And Other Snow Shelters, which covers not only igloos but trench shelters, drift caves, slab shelters, quinzee shelters, and the neat, tree-centric design you see below.

book tip via cool tools