I feel compelled to chime in since I lived in a log home from birth until about 6 months ago (bought my first house) and it all depends on who you buy from and who builds it. My parents bought from Lincoln Logs out of New York State-they've been out of business for a while now, but they made a good product. Our logs were milled so we have walls that are rounded on the outside and flat on the inside which my mom lobbied for. The logs are basically 8" thick and have a double tongue and groove milled into the tops and bottoms. Not sure what the exact R-value is, but our house is good and tight. The logs were actually soaking wet when they came off of the truck, but they were allowed to sit and bake in the sun from June to July before they were installed. They still checked and shrank a bit after they were installed and my dad spent a lot of time caulking, but we never had any bad drafts and only a few minor leaks during torrential rains. After the first two years, lots of caulk and expandable foam insulation, everything was fine. My folks have gas heat/central air and their bills have always been reasonable for the size of the home (about 2500 SF), so again, there are good and bad log home companies and good and bad log home builders. My dad probably could have avoided the headaches by going with an experienced log home builder, but he used his cousin who was a very experienced general contractor, but had never done a log home. They were both learning as they went.