After reading numerous books and listening to those who have built, you can easily cut your building costs in half compared to a standard wood frame house built by contractors. Since the inside mortar joints are insulated from the outside wall, the mortar acts as thermal mass to keep your house at a more consistent temperature. The cordwood itself is sort of an insulator and the density of the wood will have a slight effect on its efficiency. Sawdust or other materials fill in the cavity between the mortar and help insulate the walls. Cliff Shockey has written a book Stackwall Construction - Double Wall Technique .
Cliff lives in Saskatchewan, Canada and knows what it's like to build houses in cold climates.
In his book, he discusses the benefits to building two cordwood walls with a vapor barrier and insulation in between. With this technique, you can expect to gain even greater energy efficiency. Cliff's double wall technique is more time consuming and may require additional post and beam framing, but for those who want a better R value this might be the way to go. There's nothing wrong with thinning trees from a woodlot when a woodlot is managed properly. By cutting your own Double Wall Cordwood, Alberta, Canada wood, you have control over preventing any ecological damage to the land and animals.