747 Wing House
The 747 Wing House was built on the site where existing Duquette structures had burned. Some of the materials from the previous building were used as walkways. The use of the existing pad minimized site grading. The foundation used many of the existing concrete retaining walls but they were rebuilt and reinforced as required to meet new code regulations. This greatly reduced the amount of concrete needed to make the foundation and new walls. Because the wings are only supported in four primary places to the ground, the foundation was further minimized. Both main wings are held up entirely by the four large mounts that the engines originally hung from. By designing the weight distribution on the mounts, it allowed for the outside walls of the building to be made of high efficiency self-supporting glass instead of conventional load-bearing wooden walls. This maximizes solar gain for heating and allows the entire building to be opened to the outside. This also keeps it cool in the summers and minimizes the need for artificial light.
Earth shelter
In some low budget earth shelters, insulation may not be applied to the walls. These methods rely on the U factor or thermal heat storage capacity of the earth itself below the frost layer. These designs are the exception however and risk frost heave damage in colder climates. The theory behind no insulation designs relies on using the thermal mass of the earth to store heat, rather than relying on a heavy masonry or cement inner structures that exist in a typical passive solar house. This is the exception to the rule and cold temperatures may extend down into the earth above the frost line making insulation necessary for higher efficiencies.