Energy modeling can be very complex. For the novice, I would recommend either hiring an engineer or architect. If you are computer savvy, you might be able to do it yourself. DOE is the foundation for many of the programs on the market and it is the Department of Energy that funds the development of the DOE program.
Here is a list of all (most) the energy modeling software on the market.
http://apps1.eere.energy.gov/buildi...a_list.cfm You can find some that can integrate easily with a CAD program, but as I mentioned, this is really a job for a professional.