Concerned about the amount of embodied energy in concrete? An excellent way minimize concrete in the foundation for a building is to use a rubble trench.
We were recently involved in laying a rubble trench foundation for the small addition to a house near New Denver, British Columbia. The site for the building was marked using string, and a trench was dug to below the frost line, including a drainage trench running away from the building. The foundation trench was sloped towards the drainage trench to allow any water to flow quickly away and surface well beyond the building footprint.
Rigid foam insulation was placed vertically around the perimeter of the foundation trench, extending to below the frost line.