Where?

This would be in Central North Carolina

I would go ICF and 13 SEER Pump and in the long run you will be happier with that choice, though that is only my opinion.

There are people who say that geothermal isn't there yet, considering what you're asked to pay for it. http://www.radiantec.com/systems-sources/heating-sources.php But the economics would work or not work based on local conditions in central NC: favorable or unfavorable soil characteristics; local supply and demand for geothermal contractors. The tax credits assure that geothermal prices stay high, even though almost everything else in construction is depressed. Make sure you hire a contractor who knows what he is doing.
Insulation is a sure bet. These people will sell you a semi trailer load of used EPS for $3200, plus shipping. www.insulationdepot.com. Stuff it between 2x6 studs 24" OC , with more insulation and house wrap outside and a thin shell of spray polyurethane inside. Install the rest of the semi load in the attic, spend your savings on top shelf windows, and you have a house you can heat with candles.
You may still want ICF, depending on how you define long term. One day, a subsequent owner may be installing a fusion heat pump in your ICF house. (While skeptics complain that fusion isn't there yet, considering the price.)

I should add a warning not to listen to me or anyone else here on the wisdom of geothermal. Only you know what you're building. All that the rest of can do is plump for our prejudices or, worse, our financial interests. Here are three computer models that estimate heat loss and annual energy expenses, in order of sophistication:
HEED: www2.aud.ucla.edu/heed/
Hot2000: http://oee.nrcan.gc.ca/residential/personal/new-homes/r-2000/standard/hot2000.cfm?attr=4
Builditsolar.com: http://builditsolar.com/References/Calculators/HeatLoss/HeatLoss.htm
None of them will give you exactly what you need. HEED is super specific as to location and solar orientation, but lacks a geothermal option. The other two allow you to compare geothermal to a heat pump. The last is a rough guesstimate, but quite easy to do. (Dial in 400 percent as the efficiency of geothermal and 200 percent as the efficiency of a regular heat pump.)
You won't need an exact comparison for a small, tight superinsulated house. If your annual heating and cooling expenses are $1,000 or less, you don't want to pay a $15,000 premium for geothermal even if it cuts your energy use in half. At $500 a year, you'll never get that money back. Energy costs will change, of course, but you can always retrofit if and when it makes sense.

How long do you plan to live in the house? What severe weather conditions are possible in your area?

I would suggest option 2 for a couple of reasons. I always recommend constructing the bones of the house with the best possible materials. You can change lots of things on a house at a future date, but it is very difficult to upgrade the structure.

You can build a very good, tight house with 2x6s and attention to detail, but, it will never be as tight, quiet, strong and safe as an ICF home. In the long run, any HVAC system will have to be replaced. The next model will be more efficient. And if there is the possibility of tornados or hurricanes in your area, ICFs are your strongest option short of burying the home in the side of a hill.

With ICFs, you have several options. You can hire a builder for the entire project, do it yourself, or even hire an ICF installer to help you with the construction. Optimize your design with a very efficient building envelope, good windows and doors, passive solar design and a smaller HVAC system of whatever type. This will reduce your energy requirements and costs for the life of the building. You will save money every month!

Please keep in mind that my opinion is a little biased. I live in an ICF home and I am an ICF distributor, but I will never again live in anything but an ICF home.

Good luck with your project
John

Ditto what John said.

Just curious as very few folks say how much they save in energy with an ICF house. If ya don't mind John, what are your monthly elect costs now compared to your last house? Size of house then and now? Location? Type of heat/cool system before and now?

Sure, here is some data regarding energy usage. Also want to state that I could have built my home much more energy efficient, but, instead, I built what I wanted.

My house is 3400 sq ft, 1800 on the main floor and 1600 for the walkout basement, all of which is conditioned. The majority of the exterior walls are ICF with the exception of the window wall on the main floor and the wall below it in the basement. In hind site, the basement section should have been ICF instead of 2x6. All ceilings on the main floor are vaulted. All knee walls and the ceiling have 6 inches of spray foam insulation. We have 7 glass entry doors and all windows are commercial aluminum with thermal breaks (they are not energy efficient but they look good). The window wall in the living room is two sections 15’x8’ each offering a great view of the pond and woods as well as some nice solar gain on a sunny winter day. We have a two speed geothermal HVAC system with a desuperheater. Our location is near Kansas City.

The house is all electric with 5 occupants, 2 adults and 3 kids. Almost all the lighting is either halogen or CFL. We have a standard wall oven and cook top and a high efficiency washer and dryer. Beyond that, we have 4 TVs and 3 computers.

We do get a price reduction for electricity of about 20% in the winter. Our highest total energy bill from last winter was $105. The highest summer bill was $153. Months will little or no HVAC run about $65. Our winter bills are about 35% of most frame houses of similar size in our area. Summer costs are about 75%. I plan to add a couple of awnings to reduce some summer solar gain, which will reduce the summer energy costs.

Previous house was a 2000 sq ft frame house built in 1968. It had natural gas heating and central AC. Total energy costs in the winter were about $310 and about $200 in the summer.

Thanks!! That is remarkable reduced monthly charges!!  Really appreciate that John......

I am going to agree with the ICF guys. This would be a great investment as the bones of your house would be top of the line. From there you can allways make whatever changes down the line. I would also making sure to include and future plans and changes you might forsee into the current design. This way you are not limiting yourself down the line. IMHO the key building bloack of a green home is the envelope. Anything else can be upgraded down the line.

Jordan Bull
Bull Home Improvement

You wouldn't choose ICF for its energy savings. UCLA's HEED software says my all-electric house design, built with 9-inch ICF, and insulated to 150 percent of code, would use $1,310 a year in energy. The same house built with 2x6 studs 24" on center, also insulated at 150 percent of code, would use $1,331 in electricity. With wood prices where they are, the difference in construction costs could be tens of thousands of dollars.
You'd build with ICF because you want concrete walls, even in areas where termites and hurricanes aren't a threat. The wall part of ICF, as opposed to windows and doors, should stay airtight forever. While you can seal a stud wall with spray polyurethane, you'd have to build it carefully to keep it that way. And the tighter you build a stud wall, the more you risk trapping moisture inside it. Personally, I would never put EIFS (synthetic stucco) over wood studs. I want stucco, so I passed on stud walls.
I'd choose differently if I was building a house with brick veneer or cypress siding.

I really have a hard time with the last post. software programs can account for many variables, but the human factor is most important. I have yet to see a 6" stud framed wall built that will be competitative with an ICF wall as far as comfort and efficiency is concerned. Too many human variables must be perfect in order to maintain the efficiency assumed by the software.

Wes - Cannot agree with you more!!! Thankfully ICF Building Owners (Such as John C. above) pay their Utility Bills (Heating and Air) according to the "Hard" usage... and not according to some HEED "soft" ware program.

Just pointing out that the energy efficiency part of ICF, the foam boards, can be had without concrete, and for a whole lot less money. I am sympathetic to the notion of building for the ages. If you're willing to pay a premium for concrete walls, God bless you. The facts remain that 99 percent of US housing stock is stud wall construction, there are lots of folks around who are good at building them, and the home should be perfectly serviceable for your lifetime, anyway. I built a stud wall all electric home in 1982. The last year we lived in it, in 2002, the utility bills averaged $100/ month for 2400 sf of space conditioned by an 11 SEER heat pump. My renovations over 20 years -- fresh kitchen and baths, new carpet, new roof -- would been the same in an ICF house. Out of curiosity, has anyone studied whether ICF homes can claim a premium price in resale?
Donnerwetter, John Clem's experience, and my experience, mean nothing, except perhaps to neighbors who slavishly copy our building designs next door. It is impossible for the rest of us to sort out what's ICF from the other factors: geothermal, utility pricing, home design, solar orientation, windows, and on and on. You aren't helping anyone by claiming otherwise. I'll take "soft" ware over the "hard" sell any day.

Toddm,
You are correct that the energy efficiency of foam boards can be had without the concrete. They are called SIPS. And for above grade uses, I normally recommend SIPS over ICFs strickly because of the cost difference. However, SIPS or ICFs, either one, will be far better than a stud wall, no matter what the software says, no matter how dilligent you are to build the perfect wall, no matter what the cost differences might be.
Over the last 3 decades, I have built homes using almost every known system of wall construction. (No strawbales, or adobe, yet) And the only one worse than conventional stud framing is a concrete block (CMU)wall.

Our framing crew in 1982 could have stepped out of a Laurel and Hardy movie. The wife and I pulled it out after they left, and before the drywallers came, by squeezing lord knows how many tubes of caulk and shooting how many cans of foam into those walls. They were tighter in '02 than they were in '82, because I fixed infiltration points when I found them. The homeowners on this site would tend to the committed side, I am guessing. You could give them more credit. A cost benefit analysis or two wouldn't hurt either.

Good news. I googled "energy demonstration home" and discovered that the obituaries written here for the stud wall are premature, as Samuel Clemens once quipped. Habitat for Humanity's zero energy home in Denver is a double stud wall construction. In Borrego Springs, Calif, it's a bakeoff between Dow's TMass, SIPs and wood framing. In Saskatchewan it's stud walls with infiltration engineering and improved batt insulation. In Pittsburgh it's a refit of a 70-year-old stud-wall house that cut air changes by 60 percent and reduced energy use by 67 percent.
To be fair, SIPs and ICFs are well represented, too. And surely some of the interest in stud wall springs from a common sense conclusion that it's easier to bend the construction industry than change it.
That said, Wes's Worst Ever Wall System is at the heart of the Zero Energy House in Tucson, which sheathes masonry in R-14 exterior foam board. No surprises here. High thermal mass makes perfect sense in Arizona.
Which goes to show that there are no absolutes, regardless of what you read here. It depends on what you are building and where. I have never claimed that HEED has all the answers. But play with it for awhile and at least you'll have the right questions.

I don't know the cost diff between 2x4 and 2x6, if any, but you may be able to get by with 2x4 framing if you're using spray foam.  You should be able to get 3 inches of spray foam in the stud bays, giving you an effective rating of R-21.
I'm no expert-I'm sure someone here will have a better/more detailed opinion

How does one figure out how much overhang one should have on the roof trusses to let in the nice winter sun, but keep it out in the summer ?