Structural design for low embodied energy involves a compromise between complexity of form, which increases efficiency and reduces the amount of material required, and simplicity of form, that reduces the energy required for design, fabrication and construction.
In architectural structures the best compromise for low embodied energy is determined by span (the greater the span the greater the level of complexity that is justified) and load intensity (the greater the load the smaller is the justification for complexity).
The best compromise produces the lowest embodied energy and the best overall economy of means.
Reference: Structure and Architecture, Chapter 6.