The concrete walls create 'thermal mass', meaning that they store heat in cold weather, and are cool in warm weather. (I have to admit though, I really don't like this sofa! The fireplace, on the other hand...)
Again, the concrete floors were outfitted with radiant heat coils; this is more efficient as its not working really hard to heat 'dead air'. Also, the concrete works really well to store heat, therefore you can heat your home at a lower temperature. Finally, heat rises!
The abundance of windows allow for passive solar heating, and keep energy costs down by allowing in plenty of natural light. Make sure they are well insulated though (e factor), so heat isn't escaping through them. Love the reclaimed fir beams.
This is a neat feature: see the chain suspended from the eaves in the background? This is actually attached to the gutter, channeling rainwater down to the garden. Natural irrigation!
all photos: Wish