Well, Ecomodder's sister site
EcoRenovator is basically EM but for houses. The users there can help out with the entire process.
Off the top of my head though I can think of a few imporant things:
-ensure the new building meets strict levels of air sealing (beyond energy star levels), this is very important
-insulate beyond standard levels (very minimal cost for the gains and fast ROI)
-use a light colored roof, preferably one with some reflective qualities to reduce heat gain from the sun since you're primary concern is cooling
-design overhangs so you don't get direct sunlight in summer, but do in winter
There is an organization called "Passive House" that literally builds houses so they don't need heating/cooling systems (or at the most use tiny systems). You don't have to go that far, but taking a few tricks out of their playbook can really get you a long ways. I'd look for a builder experienced with passive house design to do your work. Its a different way of building that incorperates not only higher r values and superb air sealing, but also thermal brakes and some other techniques to reduce heaing/cooling energy use. You have a great chance to start over here and with passive house techniques you can come very close to eliminating heating and cooling energy usage not to mention having a very comfortable house to live in.