Editing Earth shelter (section)

==Types==
Three main types of earth shelter are described.<ref name="harral2012" /><ref name="lowimpact" /> There is also great variation in the approach to earth sheltering in terms of materials used and expenditure. The "low tech" approach might involve natural building techniques, wooden posts and shed style roofs, recycling of materials, owner labor, hand excavation, etc.<ref name="lowimpact" /> The relatively more high tech approach would be larger, using concrete and steel.<ref name="lowimpact" /> While typically more energy efficient post construction, the high tech approach has higher embodied energy and significantly more costs.<ref name="lowimpact" />

===Bermed===
In the [[Berm|earth bermed]] (also termed "bunded")<ref name="harral2012" /> type, earth is banked against the exterior walls,<ref name="lowimpact" /> sloping down away from the building. The berm can be partial or total.<ref name="harral2012" /> The polar facing wall may be bermed,<ref name="lowimpact" /> leaving the equator-facing wall un-bermed (in temperate regions). Usually this type of earth shelter is built on, or only slightly below the original [[Grade (slope)|grade]].{{citation needed|date=January 2019}} Due to the building being above the original ground level, fewer moisture problems are associated with earth berming in comparison to underground/fully-recessed construction,{{citation needed|date=January 2019}} and it costs less to construct.<ref name="roy2006" /> According to one report, earth berming provided 90-95% of the energy advantage as a completely below grade structure.<ref name="roy2006" />

===In-hill===
The in-hill (also termed "earth covered",<ref name="lowimpact" /> or "elevational")<ref name="gray2019" /> construction is where the earth shelter is set into a slope or hillside, and earth covers the roof in addition to the walls.<ref name="lowimpact" /> The most practical application is using a hill facing towards the equator (south in the [[Northern Hemisphere]] and north in the [[Southern Hemisphere]]), towards the [[Apsis|aphelion]] (north) in the [[Tropics]], or east just outside the Tropics. There is only one exposed wall in this type of earth sheltering, the wall facing out of the hill, all other walls are embedded within the earth/hill. This is the most popular and energy efficient form of earth shelter in cold and temperate climates.<ref name="terman2012" /><ref name="sterling1980" />

===Underground===
{{Main|Underground living}}
The true underground (also termed "chambered" or "subterranean") earth shelter describes a house where the ground is excavated, and the house is set in below grade. They can feature an [[Atrium (architecture)|atrium]] or courtyard<ref name="boyer1987">{{cite book |author1=LL Boyer, WT Grondzik |title=Earth shelter technology |date=1987 |publisher=Texas A & M University Press |isbn=9780890962732 |language=en|oclc=925048286 }}</ref> constructed in the middle of the shelter to provide adequate light and ventilation. The atrium is not always fully enclosed by raised ground, sometimes a U-shaped atrium is used, which is open on one side.<ref name=sterling1980 />

With an atrium earth shelter, the living spaces tend to be located around the atrium. The atrium arrangement provides a much less compact plan than that of the one or two-story bermed/in hill design; therefore it is commonly less energy efficient, in terms of heating needs.{{citation needed|date=February 2019}} Therefore, atrium designs are found mainly in warmer climates.<ref name=sterling1980>{{cite book |author1=RL Sterling |title=Earth Sheltered Buildings Construction Activity And Research In The U.S. |date=1980 |publisher=International Society for Rock Mechanics and Rock Engineering|url=https://www.onepetro.org/conference-paper/ISRM-Rockstore-1980-095}}</ref> However, the atrium does tend to trap air within it which is then heated by the sun and helps reduce heat loss.{{citation needed|date=February 2019}} Atrium designs are well suited to flat sites,<!-- <ref name=sterling1980 /> --> and are fairly common.<ref name=sterling1980 />

===Other types===
Depending on what definition of earth sheltering is used, other types are sometimes included. In culvert homes ("Cut and Cover"), precast concrete containers and large diameter pipes are arranged into a connecting design to form a living space and then backfilled with earth.<ref name="gray2019" /> An experimental construction design from the 1980s of Japan, coined '[[Alice City]]', proposed to use a wide and deep cylindrical shaft sunk into the earth, with a domed skylight roof.<ref name="gray2019" /> Artificial caves can be constructed by making a tunnel into the earth.<ref name="gray2019" /> Building greenhouses underground has also been speculated about.<ref name="oehler2007">{{cite book |author1=M Oehler |title=The earth-sheltered solar greenhouse book: how to build an energy-free year-round greenhouse |date=2007 |publisher=Mole Pub. Co. |isbn=9780960446407 |language=en|oclc=184985256 }}</ref> Schools, commercial centres, government buildings and other buildings could be built underground.<ref name="boyer1987" />