During the California heat wave of 1906, Baldassare Forestiere dug a home underground with just a pickax and shovel. He spent 40 years excavating 10 acres of rooms, tunnels, a chapel, an underground aquarium, and courtyards to experiment with underground farming. With no budget, he mixed mortar from the dirt he dug out, creating his own concrete and bricks. Despite continuing to work as a day laborer during the day (mostly digging irrigation ditches), by the 1920s, he had completed about 50 subterranean rooms.

A Sicilian immigrant to Fresno, California, Forestiere had planned to farm citrus until discovering that his 80 acres of hardpan soil were unusable for planting. Digging as far as 20 feet below the surface, Forestiere reached depths wher...

Flat House in Cambridgeshire, UK, looks like a typical barn conversion, but inside, the look and feel is something quite different. The walls remind me of hay bale dens we used to make as kids, says Flat Houses owner Gemma Barron. It has the most lovely acoustic quality. And last year we had the heating off for 24 hours in mid-winter and it stayed warm.

This comfortable home was built mostly with hemp. This fast-growing plant is a renewable resource, with carbon-capturing properties. When used in building, it typically takes the form of hempcrete, a sturdy material made by mixing hemp hurd the woody core of the plant with a binder made from water and lime. Hempcrete has both thermal mass and insulating qualities. It also continues to absorb carbon over its lifespan.

Today hempcrete is used mostly by eco-minded architects in Europe and Canada, mainly due to regulations controlling hemp production evolving in these regions. (Its not contain the psychoactive agents of regular cannabis.)

Hempcrete does not work like concrete; it cannot be used structu...