Turf housing

Turf houses, originally used in Eldurgrund and Fjordstrond, were houses built out of wood or stone and then covered in earth and allowed to grow over. These housing structures had superior insulation to other types of housing in their regions. 
Turf housing is still used in Fjordstrond, but many people live in houses carved out of the cliffs surrounding their namesake fjords. In Eldurgrund, the turf houses stand to this day, but their turf has been seared or otherwise died away, leaving only exposed looking houses beneath. This receding of the turf is a result of fire magics discovered by the humans of Eldurgrund.

Utility

They were used for increased insulation during cold times of year.