Earthsheltered buildings

Earth-sheltered buildings, including homes, are defined as those where the roof and some sides are covered by earth. Increased depth of earth cover improves the thermal performance, but this has to be balanced against consequential increased structural strength requirements. Typically, 400-50 mm of earth cover is appropriate, and the weight of this material is usually supported by concrete or masonry construction. Water exclusion is key to the design, requiring land drainage and the use of reinforced membranes.

One method of construction uses fibrous plaster shells to create the internal organic form. These are sprayed with a layer of lightweight aggregate concrete insulation, followed by 100 mm of structural concrete. After the concrete is structurally sound, the building may be fitted out and covered externally with soil and grass. An alternative construction system uses extruded polystyrene insulation between the structural concrete and the soil backfill. Either approach uses the temperature stabilising effect of the mass concrete and soil cover to significantly reduce energy consumption. In order to introduce sufficient light, at least one elevation is usually glazed and, in addition, interesting effects can be achieved with roof lights or light pipes. Ventilation may be mechanical but is normally provided through opening glazing. At the same time, unwanted cold air infiltration is eliminated by the earth enclosure.

The Hockerton Housing Project at Southwell, Nottinghamshire (Fig. 15.5) illustrates an ecological development of earth-sheltered housing in which the residents generate their own energy, harvest their own water, and recycle waste materials eliminating pollution and carbon dioxide emissions. Only the south elevation of the development overlooking the reed pond is visible, as grass covers the majority of the construction.

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