I not quite sure how you can get close to net zero in Atlanta with the 90s and humid days. Natural gas is also really cheap heat.
I do think there's a lot of things you can do to improve efficiency, but this is a tough climate to be net zero.
It was too long ago to find the link, but I remember reading an article that stated if houses in the southern US could switch the colour of their roofing material to white from (mostly) black, the sunlight reflected would lower house temperatures enough to alleviate the need for most air conditioning and save enough greenhouse gas emissions to meet (Kyoto targets?).
At least, do your own research and do the things that make obvious sense - using white on your roof, considering passive solar effects, good airflow through the house, thermal mass, energy efficient appliances, etc. Many of those can have dramatic effects with minimal added costs.
One thing to look at would be building as much of your house underground as possible - like a hobbit house. They can be designed to have lots of light and feel open and airy, but by relying on the thermal mass of the earth itself you can dramatically reduce energy costs.
It's a fun thing to research, so take some time and really get your plans figured out. A house is a huge investment, and you want to get it right. The treehugger.com design section has a lot of interesting articles on housing energy efficiency.