Houses can be built on steep surfaces and can maximize space in small areas by going below the ground. In addition the materials excavated in construction can be used in the building process.
Underground houses have less surface area so fewer building materials are used, and maintenance costs are lower. They are also wind, fire and earthquake resistant, providing a secure and safe environment in extreme weather.
One of the greatest benefits of underground living is energy efficiency. The earth's subsurface temperature remains stable, so underground dwellings benefit from geothermal mass and heat exchange, staying cool in the summer and warm in the winter. This saves around 80% in energy costs. By incorporating solar design this energy bill can be reduced to zero, providing hot water and heat to the home all year round. An additional benefit of the surrounding earth is noise insulation. Underground homes are exceptionally quiet places to live.
Finally, underground houses blend with the natural landscape, and have minimum impact on the local ecology. This is not only aesthetically pleasing but ensures that the maximum habitat is left alone for wildlife.