First Earth: Uncompromising Ecological Architecture by David Sheen is meant as an inspirational film about earthen buildings, and especially what they call ‘cob’. Cob is the oldest and easiest way of building from earth. You can find information and relevant literature here, and inspiring pictures here.
The architect Rolf Jacobsen at Gaia Tjøme, Norway, has, together with his son, built an experimental cob building on their property. Because of the cold climate they chose a two layer wall with perlite in between for insulation. You can read a discussion about cob in humid climates in this article, looking especially at the comments thread.
No matter whatever you live — in a hot, cold, dry or humid climate — lean back and watch the video below. If you enjoy it the DVD can be ordered here. (The DVD version of the film has high-quality video and audio and includes extras.)
Chapter 7 - European Earth
Chapter 8 - Arabian Earth
Chapter 9 - Urban Earth