[voyager2]

CEB has been used for centuries in Britain. Arid is obviously not a factor. It's also been used for multi-story buildings. I'm not sure how dense housing reduces pollution though. Some of the least polluting housing in the world is rural, e.g. the Amish.

edit: I should have said "earthen" construction has been used in Britain. Cob rather than CEB.

[ggcdn]

It's not possible for us all to live like the Amish. Dense housing (as opposed to sprawling single family homes) is more efficient to build, heat, provide utilities, and provide services around. It seems pretty self evident to me that urban living can produce less pollution over its lifecyle.