We just completed a design for a contemporary home. Our client was a builder so we used his home as a test subject. We designed it in a way to take full advantage of advanced framing techniques and we were able to design the home to also maximize our building materials. What we found was that there had to be several key decisions to make sure that we stayed on budget. Working as a team sharing knowledge between the builder, designer, and some key trades was crucial. The time spent up front planning proved to be a big money saver. We also found that what I call "gadgets" will drive the construction costs up, so you need to be focused on what is important to you. Gadgets would include things like solar, geothermal, and water reclamation systems. Overall, if you hire professionals that are very well versed in Building Science and green technology you can save money in some areas to be able to spend money in other areas. The extra time spent will mostly be on the front end planning and selection phase. We have been able to fine tune a system that will maximize our clients dollars and greatly increase their efficiency and sustainability of their custom designed homes. Savings all lie in the planning phase. The home needs to be designed as a system and the build team needs to have a tremendous amount of communication. Using these techniques we were able to design some high efficiency homes that were built for an incremental up charge compared to a typical custom home built in our area. Compared to a home built only to building code standards there would be a larger spread in price. My best advice would be to make sure that you communicate your desires and highly vet your team to get the most for your money. You will probably need to spend a little more money on the design process but it will pay dividends later in the build process.