Cob is a traditional material for building in many parts of the world, and there has been huge enthusiasm for this material in ecological circles, although we'd like to propose that has more to do with a consumerist mentality, today, than actual good design: clay & straw being such important materials for creating soil, which is our most urgent task nowadays, whilst we have, usually, little or no actual real need for yet more buildings.
Obvioustly where earth buildings ARE traditional, they are also probably the lowest-energy (most sustainable) option in that region, although this could have changed over the centuries (eg. if there is now plentiful rubbish that can be used for building materials).
There are far more buildings than people who need them in the western world, and design ingenuity put to use in how to retro-fit those could be much better design than letting them rot whilst we take up more space to build 'the house of our dreams')
So designing in modern times does not necessarily mean going back to 'traditional ways'. It is about adapting in the most appropriate, optimal way to actual solve the most imperative social problems we are faced with. And lack of buildings is way down the list in the modern (although lack of affordable housing certainly is: don't confuse the two).
Having said that, this is a great documentary on the subject and so full of the contrary view that we thought it useful to include, & to preface it with this introduction. As always, do your own thinking.
Intro to First Earth:
FIRST EARTH is a documentary about the movement towards a massive paradigm shift for shelter -- building healthy houses in the old ways, out of the very earth itself, and living together like in the old days, by recreating villages.
An audiovisual manifesto filmed over the course of 4 years and 4 continents, FIRST EARTH makes the case that earthen homes are the healthiest housing in the world; and that since it still takes a village to raise a healthy child, it is incumbent upon us to transform our suburban sprawl into eco-villages, a new North American dream.
FIRST EARTH official website
What's Wrong With Architecture
http://www.youtube.com/watch?v=DuDkfuziZiI
http://www.youtube.com/watch?v=11n97wW1PLQ
http://www.youtube.com/watch?v=3trjONseWiA
http://www.youtube.com/watch?v=ysOVLw30fvQ
http://www.youtube.com/watch?v=JFTwnTbLPBU
http://www.youtube.com/watch?v=AIVc7DZemTo
http://www.youtube.com/watch?v=iOeb3jv3xoU
http://www.youtube.com/watch?v=NFnzpCf5Z-g
http://www.youtube.com/watch?v=dydztLSnF78
http://www.youtube.com/watch?v=Dk64Of_HPrI
http://www.youtube.com/watch?v=DqdsSwOwD9A