I fear cold and damp. We had a cellar. Actually that cellar had the misfortune to be adjacent to an ancient clay sewerage pipe, that leaked. That got fixed, but it still was cold and damp down there.

There are lots of these in the ground hobbit houses featured in "grand designs", some I reckon are great, and some are scary. I liked the tyre one they built in France.

Around here (well more rural than here) they like straw bale houses. Fantastic insulation, and given the high density of the straw and the concrete rendering - good in a fire too. I think they made a buddist monastary or accomodation with this on Eyre peninsular and there is somebody who gives classes in how to build them.

I like high peaked roofs too - having lived far too long in flat roofed houses - can't get enough insulation - so when it's 40'C outside, its the same inside and all the heat in winter disappears too. I hate floor to ceiling glass windows for the same reason.