Earth-sheltered housing plan. Some of the insulation ideas for these houses are incredible: Soil stays at about 55°F, which cuts down on heating and cooling, and houses can be lined with used tires which maintain a regular temperature (as well as prevent concrete or trees from being used). This stuff is amazing.
Семенцов, А. Ю. "Резьба по дереву в интерьере" Современная школа, 2009 год, 256 стр.