2008 is proving to be the year of the green building code. Major cities across the country are not just encouraging, but requiring new construction to be more sustainable. Already this year, new building rules have been passed or gone into effect in Los Angeles, Dallas, New York City, and Annapolis with more on the way.

For years, cities have developed plans and voluntary standards for earth-friendlier buildings. When mandatory standards were enacted, they usually covered only public projects. Now, metro-politicians are realizing that voluntary green building standards accomplish about as much as opt-in greenhouse gas emissions control. Newer rounds of regulation affect private projects, and the truly cutting edge 'green codes' include residential construction as well.

Below, you'll find a round-up of green building codes around the U.S., the standards they use, and the key features of each.