I was doing a quick rekky in Swaziland and came across this in the Ezuluwini valley

Although these are not Earth rammed, the concept is there.

I must find the guy responsible and invite him to the build in May 2009

Thick, heat absorbant rubber that stack in piles at mosts dumps - tyres are ideal for insulation and their size and shape make for solid construction using centre stutts to mesh them together.