Lost Insulation

I saw a greeting card yesterday with the most beautiful, serene illustration of an old-fashioned Japanese countryside in winter. All the dainty, pointy houses and the tree-lined mountains that they perched upon were dusted with the merest sprinkle of new-fallen snow. Smart-lined ladies strolled the wooden walkways, jet-black hair done up with chopsticks, protecting their vibrant-dyed kimonos with equally technicolor parasols. It made me realize I'd never considered winter in Japan before, though of course I knew it had one. And as I meditated on the details of this sublime and quiet scene, the thought that floated up into my conscious mind was...

How in heaven did they heat those pretty paper houses?