Does one need a general contractors license to build green homes, or can you simply just hire a general contractor? Are there advantages to either? How does this work in California?

Some municipalities will let you build on a "homeowners" permit for a home you ultimately occupy.
Most municipalities will not let you be a contractor for hire without some sort of licensing or certification.
Folks who employ contractors should be aware of the rules for their city or state and make sure they are followed.

Inspectors and building departments can intervene most effectively when contractor pulls permits and is the contractor of record. In MI there is even a fund contributed to by licensed contractors to correct situations caused by licensed individuals who don't take care of them themselves.

One should never pull a permit "for" someone else as you become the contractor of record and the only one a building department can go after for problem resolution.

While general contractors will take a percentage of the job, they are also likely to get lower cost from the trade contractors and material suppliers. Many companies will charge more when a homeowner is the GC because they suspect the job won't go as smoothly. While one can get most of what they need for a stick built house at big box store for competitive prices, green homes have things that won't be there and a contractor can still get cheaper.

good luck,
joe

Joe, Well said.

Military veterans get a 10% discount at Lowes and Home Depot. That can really add up over time. It always pays to ask where you shop for supplies - the worst they can say is no.

-Rosalinda