Log homes are actually more energy efficient than conventional ones! So long as it’s been properly built, and has been properly chinked, your log home could be 15-20% more energy efficient than your typical home.
This is due in part to log home builders mostly trying to meet the DOE’s “Energy Star” standards, which mean those buildings are 30% more energy efficient than building codes stipulate.
PLUS, they’re more environmentally friendly by nature! They’re constructed from natural and renewable materials, and if the home is deconstructed in the future, its parts can be reused, as opposed to just sitting in a landfill!