It's hard for me to grasp, after reading so much from log home owners who talk about how comfortable their home is and how easy they are to heat and cool, even in much harsher climates. But I surely see how difficult it could be to seal them well. I've lived in places that are much, much colder than NC. However I grew up in SC and understand the necessity of dehumidifying also! I now live in Illinois in a stick built house that was insulated to code at the time it was built, 1982, and either the heat or ac has to be going about 360 days a year. When it's 10 deg in the winter, or 98 deg in the summer, the heat pump can barely keep up. In the summer we could fry breakfast on the roof and cook dinner in the attic. In the winter the crawl space could keep our food in deep freeze. It's a very uncomfortable house, even after all the extra sealing I've done, and adding storm windows.
There's lots and lots of things I have to consider. I've done so much reading about log homes, including writings from researchers who've lived in log homes who insist log homes can't be judged on the true R value of logs alone. They attest to the long period of time it takes for the temperature to change in a log house. Most real log homes are built with logs that are at least 10", usually 12" or more. At an R value of 1.4 per inch, that's at least R-14. I'm not building a home with 6" milled "logs". Here's also a bit about R-value/thermal mass of logs... http://energy.gov/energysaver/articles/energy-efficiency-log-homes
I understand most likely your largest concern would be the leaks around the logs, but I don't necessarily want to live in a box that's so tight we'd suffocate if our ventilation system shut down either. Of course there's maintenance to consider to keep leaks out. There's a huge group of people who say they do very little maintenance after the first few years, and when they do it costs very little. You don't have to use chinking made by a corporation that costs $250 a bucket. Have you heard of these guys?: http://www.buildloghomes.org/
After much research and consideration with my wife I went to their seminar, so I already have a few grand into the project, not to mention the bias I now have after all the planning, etc...
I've also considered the short distance materials would have to be shipped, and eliminating materials that are manufactured by nasty corporations with most likely harmful industrial processes. I've been looking into plaster for interior walls that I can make with local materials. I'd need concrete like any other home, insulation in the roof and floor, but would be doing away with huge amounts of materials that would have to be shipped.
I think my idea is that I can live very comfortably in a house that's not airtight, and can sleep soundly if I'm using sustainable energy to heat/cool it.
About radiant floors... I figured we'd need radiant floors to keep our feet from freezing since we want tile floors with some type of concrete underneath for thermal mass. Even with a good passive solar design, on days when the sun is not shining wouldn't our feet freeze on top of all that concrete and tile? Obviously I plan to have lots of insulation under those floors, but wouldn't they still be chilly no matter how much warm air was blasting about?
Thanks to you I'm learning so much more about geothermal heat pumps. It certainly seems like a better way to go considering such need for A/C. Aren't these systems compatible with radiant heating? I understand the added cost, but I plan to build my own house with my own two hands, hiring out very little. I'm sure I can lay the tubing before concrete is poured.