Here's a taste of the (excellent IMO) article:
And Gardiner said when they finally got tired of the old wood-burning stove she telephoned the propane dealer in Kindersley. “He asked if I needed a wall vent or a ceiling vent,” she recalled. “I told him my walls are four feet thick.” A few months after the propane system was installed, she remembered the propane man saying, “You’re not using much propane. If all my customers were like you, I’d go broke.” She attributed the low usage to the superb insulating efficiency of the sod; which is now being re-discovered by conservationists as the latest in energy-efficient housing.