In the interests of full disclosure, I am a member of the International Code Council's team crafting a Green Building Code.
Accoding to the ICC:
The objective of this new project is to develop a Green Building Code for traditional and high-performance buildings that is consistent and coordinated with the ICC family of Codes and Standards.
After LEED, Green Globes, BREEM, Energy Star, NAHB Green and the prospective ASHRAE 189, why on earth do we need another green building standard? Is it simply to give people like me something to do in their spare time (I had thought about taking up knitting)? The answer is definitely not.
As articulated above, the point of the ICC Green Building Code is to be consistent with the other I-codes which most jurisdictions have adopted (or tweaked) as the basis of their building codes. Thus, builders building green buildings must adhere to two standards at least--the conventional I-Code based building code, and the green building standard. This has caused many issues, including the waterless urinal fiasco, in which waterless urinals were prohibited under conventional code provisions. By integrating a green building standard with the building code, these types of headaches can be minimized.
In addition, code officials and policiticians are comfortable with adopting and utlizing I-Codes as the basis for building regulations. Thus, municipalities do not have to reinvent the code wheel when looking to implement green building practices.
Finally, a solid compromise green building code can advance green building as the default standard. In California, which has adopted a green building code, various interest groups, including the California Building Industry Association, have come on board with the code.
There will always be a place for aspirational green building standards. LEED, for example, should provide new and innovative and more challenging ways to reduce GHG emissions, materials usage, enhance energy efficiency, etc. The goal of a code, however, should be to raise the floor of all buildings to a greener baseline. ICC's Green Building Code effort is a step towards making that happen. So, for me, knitting will have to wait.